widget.cpp

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/*
 * This file is part of OpenTTD.
 * OpenTTD is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, version 2.
 * OpenTTD is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
 * See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with OpenTTD. If not, see <https://www.gnu.org/licenses/old-licenses/gpl-2.0>.
 */

 
#include "stdafx.h"
#include "core/backup_type.hpp"
#include "company_func.h"
#include "settings_gui.h"
#include "strings_type.h"
#include "window_gui.h"
#include "viewport_func.h"
#include "zoom_func.h"
#include "strings_func.h"
#include "transparency.h"
#include "core/geometry_func.hpp"
#include "settings_type.h"
#include "querystring_gui.h"
 
#include "table/sprites.h"
#include "table/strings.h"
#include "table/string_colours.h"
 
#include "safeguards.h"
 
WidgetDimensions WidgetDimensions::scaled = {};
 
static std::string GetStringForWidget(const Window *w, const NWidgetCore *nwid, bool secondary = false)
{
  StringID stringid = nwid->GetString();
  if (nwid->GetIndex() < 0) {
    if (stringid == STR_NULL) return {};
 
    return GetString(stringid + (secondary ? 1 : 0));
  }
 
  return w->GetWidgetString(nwid->GetIndex(), stringid + (secondary ? 1 : 0));
}

static inline RectPadding ScaleGUITrad(const RectPadding &r)
{
  return {(uint8_t)ScaleGUITrad(r.left), (uint8_t)ScaleGUITrad(r.top), (uint8_t)ScaleGUITrad(r.right), (uint8_t)ScaleGUITrad(r.bottom)};
}

static inline Dimension ScaleGUITrad(const Dimension &dim)
{
  return {(uint)ScaleGUITrad(dim.width), (uint)ScaleGUITrad(dim.height)};
}

Dimension GetScaledSpriteSize(SpriteID sprid)
{
  Point offset;
  Dimension d = GetSpriteSize(sprid, &offset, ZoomLevel::Normal);
  d.width  -= offset.x;
  d.height -= offset.y;
  return ScaleGUITrad(d);
}

void SetupWidgetDimensions()
{
  WidgetDimensions::scaled.imgbtn       = ScaleGUITrad(WidgetDimensions::unscaled.imgbtn);
  WidgetDimensions::scaled.inset        = ScaleGUITrad(WidgetDimensions::unscaled.inset);
  WidgetDimensions::scaled.vscrollbar   = ScaleGUITrad(WidgetDimensions::unscaled.vscrollbar);
  WidgetDimensions::scaled.hscrollbar   = ScaleGUITrad(WidgetDimensions::unscaled.hscrollbar);
  if (_settings_client.gui.scale_bevels) {
    WidgetDimensions::scaled.bevel    = ScaleGUITrad(WidgetDimensions::unscaled.bevel);
  } else {
    WidgetDimensions::scaled.bevel    = WidgetDimensions::unscaled.bevel;
  }
  WidgetDimensions::scaled.fullbevel    = ScaleGUITrad(WidgetDimensions::unscaled.fullbevel);
  WidgetDimensions::scaled.framerect    = ScaleGUITrad(WidgetDimensions::unscaled.framerect);
  WidgetDimensions::scaled.frametext    = ScaleGUITrad(WidgetDimensions::unscaled.frametext);
  WidgetDimensions::scaled.matrix       = ScaleGUITrad(WidgetDimensions::unscaled.matrix);
  WidgetDimensions::scaled.shadebox     = ScaleGUITrad(WidgetDimensions::unscaled.shadebox);
  WidgetDimensions::scaled.stickybox    = ScaleGUITrad(WidgetDimensions::unscaled.stickybox);
  WidgetDimensions::scaled.debugbox     = ScaleGUITrad(WidgetDimensions::unscaled.debugbox);
  WidgetDimensions::scaled.defsizebox   = ScaleGUITrad(WidgetDimensions::unscaled.defsizebox);
  WidgetDimensions::scaled.resizebox    = ScaleGUITrad(WidgetDimensions::unscaled.resizebox);
  WidgetDimensions::scaled.closebox     = ScaleGUITrad(WidgetDimensions::unscaled.closebox);
  WidgetDimensions::scaled.captiontext  = ScaleGUITrad(WidgetDimensions::unscaled.captiontext);
  WidgetDimensions::scaled.dropdowntext = ScaleGUITrad(WidgetDimensions::unscaled.dropdowntext);
  WidgetDimensions::scaled.dropdownlist = ScaleGUITrad(WidgetDimensions::unscaled.dropdownlist);
  WidgetDimensions::scaled.modalpopup   = ScaleGUITrad(WidgetDimensions::unscaled.modalpopup);
 
  WidgetDimensions::scaled.vsep_normal  = ScaleGUITrad(WidgetDimensions::unscaled.vsep_normal);
  WidgetDimensions::scaled.vsep_wide    = ScaleGUITrad(WidgetDimensions::unscaled.vsep_wide);
  WidgetDimensions::scaled.hsep_normal  = ScaleGUITrad(WidgetDimensions::unscaled.hsep_normal);
  WidgetDimensions::scaled.hsep_wide    = ScaleGUITrad(WidgetDimensions::unscaled.hsep_wide);
  WidgetDimensions::scaled.hsep_indent  = ScaleGUITrad(WidgetDimensions::unscaled.hsep_indent);
}

static inline Point GetAlignedPosition(const Rect &r, const Dimension &d, StringAlignment align)
{
  Point p;
  /* In case we have a RTL language we swap the alignment. */
  if (!(align & SA_FORCE) && _current_text_dir == TD_RTL && (align & SA_HOR_MASK) != SA_HOR_CENTER) align ^= SA_RIGHT;
  switch (align & SA_HOR_MASK) {
    case SA_LEFT:       p.x = r.left; break;
    case SA_HOR_CENTER: p.x = CentreBounds(r.left, r.right, d.width); break;
    case SA_RIGHT:      p.x = r.right + 1 - d.width; break;
    default: NOT_REACHED();
  }
  switch (align & SA_VERT_MASK) {
    case SA_TOP:         p.y = r.top; break;
    case SA_VERT_CENTER: p.y = CentreBounds(r.top, r.bottom, d.height); break;
    case SA_BOTTOM:      p.y = r.bottom + 1 - d.height; break;
    default: NOT_REACHED();
  }
  return p;
}

static std::pair<int, int> HandleScrollbarHittest(const Scrollbar *sb, int mi, int ma, bool horizontal)
{
  /* Base for reversion */
  int rev_base = mi + ma;
  int button_size = horizontal ? NWidgetScrollbar::GetHorizontalDimension().width : NWidgetScrollbar::GetVerticalDimension().height;
 
  mi += button_size; // now points to just after the up/left-button
  ma -= button_size; // now points to just before the down/right-button
 
  int count = sb->GetCount();
  int cap = sb->GetCapacity();
 
  if (count > cap) {
    int height = ma + 1 - mi;
    int slider_height = std::max(button_size, cap * height / count);
    height -= slider_height;
 
    mi += height * sb->GetPosition() / (count - cap);
    ma = mi + slider_height - 1;
  }
 
  /* Reverse coordinates for RTL. */
  if (horizontal && _current_text_dir == TD_RTL) return {rev_base - ma, rev_base - mi};
 
  return {mi, ma};
}

static void ScrollbarClickPositioning(Window *w, NWidgetScrollbar *sb, int x, int y, int mi, int ma)
{
  int pos;
  int button_size;
  bool rtl = false;
  bool changed = false;
 
  if (sb->type == NWID_HSCROLLBAR) {
    pos = x;
    rtl = _current_text_dir == TD_RTL;
    button_size = NWidgetScrollbar::GetHorizontalDimension().width;
  } else {
    pos = y;
    button_size = NWidgetScrollbar::GetVerticalDimension().height;
  }
  if (pos < mi + button_size) {
    /* Pressing the upper button? */
    sb->disp_flags.Set(NWidgetDisplayFlag::ScrollbarUp);
    if (_scroller_click_timeout <= 1) {
      _scroller_click_timeout = 3;
      changed = sb->UpdatePosition(rtl ? 1 : -1);
    }
    w->mouse_capture_widget = sb->GetIndex();
  } else if (pos >= ma - button_size) {
    /* Pressing the lower button? */
    sb->disp_flags.Set(NWidgetDisplayFlag::ScrollbarDown);
 
    if (_scroller_click_timeout <= 1) {
      _scroller_click_timeout = 3;
      changed = sb->UpdatePosition(rtl ? -1 : 1);
    }
    w->mouse_capture_widget = sb->GetIndex();
  } else {
    auto [start, end] = HandleScrollbarHittest(sb, mi, ma, sb->type == NWID_HSCROLLBAR);
 
    if (pos < start) {
      changed = sb->UpdatePosition(rtl ? 1 : -1, Scrollbar::SS_BIG);
    } else if (pos > end) {
      changed = sb->UpdatePosition(rtl ? -1 : 1, Scrollbar::SS_BIG);
    } else {
      _scrollbar_start_pos = start - mi - button_size;
      _scrollbar_size = ma - mi - button_size * 2 - (end - start);
      w->mouse_capture_widget = sb->GetIndex();
      _cursorpos_drag_start = _cursor.pos;
    }
  }
 
  if (changed) {
    /* Position changed so refresh the window */
    w->OnScrollbarScroll(sb->GetIndex());
    w->SetDirty();
  } else {
    /* No change so only refresh this scrollbar */
    sb->SetDirty(w);
  }
}

void ScrollbarClickHandler(Window *w, NWidgetCore *nw, int x, int y)
{
  int mi, ma;
 
  if (nw->type == NWID_HSCROLLBAR) {
    mi = nw->pos_x;
    ma = nw->pos_x + nw->current_x;
  } else {
    mi = nw->pos_y;
    ma = nw->pos_y + nw->current_y;
  }
  NWidgetScrollbar *scrollbar = dynamic_cast<NWidgetScrollbar*>(nw);
  assert(scrollbar != nullptr);
  ScrollbarClickPositioning(w, scrollbar, x, y, mi, ma);
}

WidgetID GetWidgetFromPos(const Window *w, int x, int y)
{
  NWidgetCore *nw = w->nested_root->GetWidgetFromPos(x, y);
  return (nw != nullptr) ? nw->GetIndex() : INVALID_WIDGET;
}

void DrawFrameRect(int left, int top, int right, int bottom, Colours colour, FrameFlags flags)
{
  if (flags.Test(FrameFlag::Transparent)) {
    GfxFillRect(left, top, right, bottom, PALETTE_TO_TRANSPARENT, FILLRECT_RECOLOUR);
  } else {
    assert(colour < COLOUR_END);
 
    const PixelColour dark         = GetColourGradient(colour, SHADE_DARK);
    const PixelColour medium_dark  = GetColourGradient(colour, SHADE_LIGHT);
    const PixelColour medium_light = GetColourGradient(colour, SHADE_LIGHTER);
    const PixelColour light        = GetColourGradient(colour, SHADE_LIGHTEST);
    PixelColour interior;
 
    Rect outer = {left, top, right, bottom};                   // Outside rectangle
    Rect inner = outer.Shrink(WidgetDimensions::scaled.bevel); // Inside rectangle
 
    if (flags.Test(FrameFlag::Lowered)) {
      GfxFillRect(outer.left,      outer.top,        inner.left - 1,  outer.bottom, dark);   // Left
      GfxFillRect(inner.left,      outer.top,        outer.right,     inner.top - 1, dark);  // Top
      GfxFillRect(inner.right + 1, inner.top,        outer.right,     inner.bottom,  light); // Right
      GfxFillRect(inner.left,      inner.bottom + 1, outer.right,     outer.bottom, light);  // Bottom
      interior = (flags.Test(FrameFlag::Darkened) ? medium_dark : medium_light);
    } else {
      GfxFillRect(outer.left,      outer.top,        inner.left - 1, inner.bottom,  light); // Left
      GfxFillRect(inner.left,      outer.top,        inner.right,    inner.top - 1, light); // Top
      GfxFillRect(inner.right + 1, outer.top,        outer.right,    inner.bottom,  dark);  // Right
      GfxFillRect(outer.left,      inner.bottom + 1, outer.right,    outer.bottom, dark);   // Bottom
      interior = medium_dark;
    }
    if (!flags.Test(FrameFlag::BorderOnly)) {
      GfxFillRect(inner.left,  inner.top, inner.right, inner.bottom, interior); // Inner
    }
  }
}
 
void DrawSpriteIgnorePadding(SpriteID img, PaletteID pal, const Rect &r, StringAlignment align)
{
  Point offset;
  Dimension d = GetSpriteSize(img, &offset);
  d.width  -= offset.x;
  d.height -= offset.y;
 
  Point p = GetAlignedPosition(r, d, align);
  DrawSprite(img, pal, p.x - offset.x, p.y - offset.y);
}

static inline void DrawImageButtons(const Rect &r, WidgetType type, Colours colour, bool clicked, SpriteID img, StringAlignment align)
{
  assert(img != 0);
  DrawFrameRect(r, colour, clicked ? FrameFlag::Lowered : FrameFlags{});
 
  if ((type & WWT_MASK) == WWT_IMGBTN_2 && clicked) img++; // Show different image when clicked for #WWT_IMGBTN_2.
  DrawSpriteIgnorePadding(img, PAL_NONE, r, align);
}

static inline void DrawImageTextButtons(const Rect &r, Colours colour, bool clicked, SpriteID img, TextColour text_colour, const std::string &text, StringAlignment align, FontSize fs)
{
  DrawFrameRect(r, colour, clicked ? FrameFlag::Lowered : FrameFlags{});
 
  bool rtl = _current_text_dir == TD_RTL;
  int image_width = img != 0 ? GetScaledSpriteSize(img).width : 0;
  Rect r_img = r.Shrink(WidgetDimensions::scaled.framerect).WithWidth(image_width, rtl);
  Rect r_text = r.Shrink(WidgetDimensions::scaled.framerect).Indent(image_width + WidgetDimensions::scaled.hsep_wide, rtl);
 
  if (img != 0) {
    DrawSpriteIgnorePadding(img, PAL_NONE, r_img, SA_HOR_CENTER | (align & SA_VERT_MASK));
  }
 
  if (!text.empty()) {
    Dimension d = GetStringBoundingBox(text, fs);
    Point p = GetAlignedPosition(r_text, d, align);
    DrawString(r_text.left, r_text.right, p.y, text, text_colour, align, false, fs);
  }
}

static inline void DrawLabel(const Rect &r, TextColour colour, std::string_view str, StringAlignment align, FontSize fs)
{
  if (str.empty()) return;
 
  Dimension d = GetStringBoundingBox(str, fs);
  Point p = GetAlignedPosition(r, d, align);
  DrawString(r.left, r.right, p.y, str, colour, align, false, fs);
}

static inline void DrawText(const Rect &r, TextColour colour, std::string_view str, StringAlignment align, FontSize fs)
{
  if (str.empty()) return;
 
  Dimension d = GetStringBoundingBox(str, fs);
  Point p = GetAlignedPosition(r, d, align);
  DrawString(r.left, r.right, p.y, str, colour, align, false, fs);
}

static inline void DrawInset(const Rect &r, Colours colour, TextColour text_colour, std::string_view str, StringAlignment align, FontSize fs)
{
  DrawFrameRect(r, colour, {FrameFlag::Lowered, FrameFlag::Darkened});
  if (!str.empty()) DrawString(r.Shrink(WidgetDimensions::scaled.inset), str, text_colour, align, false, fs);
}

static inline void DrawMatrix(const Rect &r, Colours colour, bool clicked, uint32_t num_columns, uint32_t num_rows, uint resize_x, uint resize_y)
{
  DrawFrameRect(r, colour, clicked ? FrameFlag::Lowered : FrameFlags{});
 
  int column_width; // Width of a single column in the matrix.
  if (num_columns == 0) {
    column_width = resize_x;
    num_columns = r.Width() / column_width;
  } else {
    column_width = r.Width() / num_columns;
  }
 
  int row_height; // Height of a single row in the matrix.
  if (num_rows == 0) {
    row_height = resize_y;
    num_rows = r.Height() / row_height;
  } else {
    row_height = r.Height() / num_rows;
  }
 
  PixelColour col = GetColourGradient(colour, SHADE_LIGHTER);
 
  int x = r.left;
  for (int ctr = num_columns; ctr > 1; ctr--) {
    x += column_width;
    GfxFillRect(x, r.top + WidgetDimensions::scaled.bevel.top, x + WidgetDimensions::scaled.bevel.left - 1, r.bottom - WidgetDimensions::scaled.bevel.bottom, col);
  }
 
  x = r.top;
  for (int ctr = num_rows; ctr > 1; ctr--) {
    x += row_height;
    GfxFillRect(r.left + WidgetDimensions::scaled.bevel.left, x, r.right - WidgetDimensions::scaled.bevel.right, x + WidgetDimensions::scaled.bevel.top - 1, col);
  }
 
  col = GetColourGradient(colour, SHADE_NORMAL);
 
  x = r.left - 1;
  for (int ctr = num_columns; ctr > 1; ctr--) {
    x += column_width;
    GfxFillRect(x - WidgetDimensions::scaled.bevel.right + 1, r.top + WidgetDimensions::scaled.bevel.top, x, r.bottom - WidgetDimensions::scaled.bevel.bottom, col);
  }
 
  x = r.top - 1;
  for (int ctr = num_rows; ctr > 1; ctr--) {
    x += row_height;
    GfxFillRect(r.left + WidgetDimensions::scaled.bevel.left, x - WidgetDimensions::scaled.bevel.bottom + 1, r.right - WidgetDimensions::scaled.bevel.right, x, col);
  }
}

static inline void DrawVerticalScrollbar(const Rect &r, Colours colour, bool up_clicked, bool bar_dragged, bool down_clicked, const Scrollbar *scrollbar)
{
  int height = NWidgetScrollbar::GetVerticalDimension().height;
 
  /* draw up/down buttons */
  DrawImageButtons(r.WithHeight(height, false),  NWID_VSCROLLBAR, colour, up_clicked,   SPR_ARROW_UP,   SA_CENTER);
  DrawImageButtons(r.WithHeight(height, true),   NWID_VSCROLLBAR, colour, down_clicked, SPR_ARROW_DOWN, SA_CENTER);
 
  PixelColour c1 = GetColourGradient(colour, SHADE_DARK);
  PixelColour c2 = GetColourGradient(colour, SHADE_LIGHTEST);
 
  /* draw "shaded" background */
  Rect bg = r.Shrink(0, height);
  GfxFillRect(bg, c2);
  GfxFillRect(bg, c1, FILLRECT_CHECKER);
 
  /* track positions. These fractions are based on original 1x dimensions, but scale better. */
  int left  = r.left + r.Width() * 3 / 11; /*  left track is positioned 3/11ths from the left */
  int right = r.left + r.Width() * 8 / 11; /* right track is positioned 8/11ths from the left */
  const uint8_t bl = WidgetDimensions::scaled.bevel.left;
  const uint8_t br = WidgetDimensions::scaled.bevel.right;
 
  /* draw shaded lines */
  GfxFillRect(bg.WithX(left - bl,  left       - 1), c1);
  GfxFillRect(bg.WithX(left,       left + br  - 1), c2);
  GfxFillRect(bg.WithX(right - bl, right      - 1), c1);
  GfxFillRect(bg.WithX(right,      right + br - 1), c2);
 
  auto [top, bottom] = HandleScrollbarHittest(scrollbar, r.top, r.bottom, false);
  DrawFrameRect(r.left, top, r.right, bottom, colour, bar_dragged ? FrameFlag::Lowered : FrameFlags{});
}

static inline void DrawHorizontalScrollbar(const Rect &r, Colours colour, bool left_clicked, bool bar_dragged, bool right_clicked, const Scrollbar *scrollbar)
{
  int width = NWidgetScrollbar::GetHorizontalDimension().width;
 
  DrawImageButtons(r.WithWidth(width, false), NWID_HSCROLLBAR, colour, left_clicked,  SPR_ARROW_LEFT,  SA_CENTER);
  DrawImageButtons(r.WithWidth(width, true),  NWID_HSCROLLBAR, colour, right_clicked, SPR_ARROW_RIGHT, SA_CENTER);
 
  PixelColour c1 = GetColourGradient(colour, SHADE_DARK);
  PixelColour c2 = GetColourGradient(colour, SHADE_LIGHTEST);
 
  /* draw "shaded" background */
  Rect bg = r.Shrink(width, 0);
  GfxFillRect(bg, c2);
  GfxFillRect(bg, c1, FILLRECT_CHECKER);
 
  /* track positions. These fractions are based on original 1x dimensions, but scale better. */
  int top    = r.top + r.Height() * 3 / 11; /*    top track is positioned 3/11ths from the top */
  int bottom = r.top + r.Height() * 8 / 11; /* bottom track is positioned 8/11ths from the top */
  const uint8_t bt = WidgetDimensions::scaled.bevel.top;
  const uint8_t bb = WidgetDimensions::scaled.bevel.bottom;
 
  /* draw shaded lines */
  GfxFillRect(bg.WithY(top - bt,    top         - 1), c1);
  GfxFillRect(bg.WithY(top,         top + bb    - 1), c2);
  GfxFillRect(bg.WithY(bottom - bt, bottom      - 1), c1);
  GfxFillRect(bg.WithY(bottom,      bottom + bb - 1), c2);
 
  /* draw actual scrollbar */
  auto [left, right] = HandleScrollbarHittest(scrollbar, r.left, r.right, true);
  DrawFrameRect(left, r.top, right, r.bottom, colour, bar_dragged ? FrameFlag::Lowered : FrameFlags{});
}

static inline void DrawFrame(const Rect &r, Colours colour, TextColour text_colour, std::string_view str, StringAlignment align, FontSize fs)
{
  int x2 = r.left; // by default the left side is the left side of the widget
 
  if (!str.empty()) x2 = DrawString(r.left + WidgetDimensions::scaled.frametext.left, r.right - WidgetDimensions::scaled.frametext.right, r.top, str, text_colour, align, false, fs);
 
  PixelColour c1 = GetColourGradient(colour, SHADE_DARK);
  PixelColour c2 = GetColourGradient(colour, SHADE_LIGHTEST);
 
  /* If the frame has text, adjust the top bar to fit half-way through */
  Rect inner = r.Shrink(ScaleGUITrad(1));
  if (!str.empty()) inner.top = r.top + GetCharacterHeight(FS_NORMAL) / 2;
 
  Rect outer  = inner.Expand(WidgetDimensions::scaled.bevel);
  Rect inside = inner.Shrink(WidgetDimensions::scaled.bevel);
 
  if (_current_text_dir == TD_LTR) {
    /* Line from upper left corner to start of text */
    GfxFillRect(outer.left, outer.top, r.left + WidgetDimensions::scaled.frametext.left - WidgetDimensions::scaled.bevel.left - 1, inner.top  - 1, c1);
    GfxFillRect(inner.left, inner.top, r.left + WidgetDimensions::scaled.frametext.left - WidgetDimensions::scaled.bevel.left - 1, inside.top - 1, c2);
 
    /* Line from end of text to upper right corner */
    GfxFillRect(x2 + WidgetDimensions::scaled.bevel.right, outer.top, inner.right,  inner.top  - 1, c1);
    GfxFillRect(x2 + WidgetDimensions::scaled.bevel.right, inner.top, inside.right, inside.top - 1, c2);
  } else {
    /* Line from upper left corner to start of text */
    GfxFillRect(outer.left, outer.top, x2 - WidgetDimensions::scaled.bevel.left - 1, inner.top  - 1, c1);
    GfxFillRect(inner.left, inner.top, x2 - WidgetDimensions::scaled.bevel.left - 1, inside.top - 1, c2);
 
    /* Line from end of text to upper right corner */
    GfxFillRect(r.right - WidgetDimensions::scaled.frametext.right + WidgetDimensions::scaled.bevel.right, outer.top, inner.right,  inner.top  - 1, c1);
    GfxFillRect(r.right - WidgetDimensions::scaled.frametext.right + WidgetDimensions::scaled.bevel.right, inner.top, inside.right, inside.top - 1, c2);
  }
 
  /* Line from upper left corner to bottom left corner */
  GfxFillRect(outer.left, inner.top,  inner.left  - 1, inner.bottom,  c1);
  GfxFillRect(inner.left, inside.top, inside.left - 1, inside.bottom, c2);
 
  /* Line from upper right corner to bottom right corner */
  GfxFillRect(inside.right + 1, inner.top, inner.right, inside.bottom, c1);
  GfxFillRect(inner.right  + 1, outer.top, outer.right, inner.bottom,  c2);
 
  /* Line from bottom left corner to bottom right corner */
  GfxFillRect(inner.left, inside.bottom + 1, inner.right, inner.bottom, c1);
  GfxFillRect(outer.left, inner.bottom  + 1, outer.right, outer.bottom, c2);
}

static inline void DrawShadeBox(const Rect &r, Colours colour, bool clicked)
{
  DrawImageButtons(r, WWT_SHADEBOX, colour, clicked, clicked ? SPR_WINDOW_SHADE: SPR_WINDOW_UNSHADE, SA_CENTER);
}

static inline void DrawStickyBox(const Rect &r, Colours colour, bool clicked)
{
  DrawImageButtons(r, WWT_STICKYBOX, colour, clicked, clicked ? SPR_PIN_UP : SPR_PIN_DOWN, SA_CENTER);
}

static inline void DrawDefSizeBox(const Rect &r, Colours colour, bool clicked)
{
  DrawImageButtons(r, WWT_DEFSIZEBOX, colour, clicked, SPR_WINDOW_DEFSIZE, SA_CENTER);
}

static inline void DrawDebugBox(const Rect &r, Colours colour, bool clicked)
{
  DrawImageButtons(r, WWT_DEBUGBOX, colour, clicked, SPR_WINDOW_DEBUG, SA_CENTER);
}

static inline void DrawResizeBox(const Rect &r, Colours colour, bool at_left, bool clicked, bool bevel)
{
  if (bevel) {
    DrawFrameRect(r, colour, clicked ? FrameFlag::Lowered : FrameFlags{});
  } else if (clicked) {
    GfxFillRect(r.Shrink(WidgetDimensions::scaled.bevel), GetColourGradient(colour, SHADE_LIGHTER));
  }
  DrawSpriteIgnorePadding(at_left ? SPR_WINDOW_RESIZE_LEFT : SPR_WINDOW_RESIZE_RIGHT, PAL_NONE, r.Shrink(ScaleGUITrad(2)), at_left ? (SA_LEFT | SA_BOTTOM | SA_FORCE) : (SA_RIGHT | SA_BOTTOM | SA_FORCE));
}

static inline void DrawCloseBox(const Rect &r, Colours colour)
{
  if (colour != COLOUR_WHITE) DrawFrameRect(r, colour, {});
  Point offset;
  Dimension d = GetSpriteSize(SPR_CLOSEBOX, &offset);
  d.width  -= offset.x;
  d.height -= offset.y;
  int s = ScaleSpriteTrad(1); // Offset to account for shadow of SPR_CLOSEBOX.
  DrawSprite(SPR_CLOSEBOX, (colour != COLOUR_WHITE ? TC_BLACK : TC_SILVER) | (1U << PALETTE_TEXT_RECOLOUR), CentreBounds(r.left, r.right, d.width - s) - offset.x, CentreBounds(r.top, r.bottom, d.height - s) - offset.y);
}

void DrawCaption(const Rect &r, Colours colour, Owner owner, TextColour text_colour, std::string_view str, StringAlignment align, FontSize fs)
{
  bool company_owned = owner < MAX_COMPANIES;
 
  DrawFrameRect(r, colour, FrameFlag::BorderOnly);
  Rect ir = r.Shrink(WidgetDimensions::scaled.bevel);
  DrawFrameRect(ir, colour, company_owned ? FrameFlags{FrameFlag::Lowered, FrameFlag::Darkened, FrameFlag::BorderOnly} : FrameFlags{FrameFlag::Lowered, FrameFlag::Darkened});
 
  if (company_owned) {
    GfxFillRect(ir.Shrink(WidgetDimensions::scaled.bevel), GetColourGradient(_company_colours[owner], SHADE_NORMAL));
  }
 
  if (str.empty()) return;
 
  Dimension d = GetStringBoundingBox(str);
  Point p = GetAlignedPosition(r, d, align);
  DrawString(r.left + WidgetDimensions::scaled.captiontext.left, r.right - WidgetDimensions::scaled.captiontext.left, p.y, str, text_colour, align, false, fs);
}

static inline void DrawButtonDropdown(const Rect &r, Colours colour, bool clicked_button, bool clicked_dropdown, std::string_view str, StringAlignment align)
{
  bool rtl = _current_text_dir == TD_RTL;
 
  Rect text = r.Indent(NWidgetLeaf::dropdown_dimension.width, !rtl);
  DrawFrameRect(text, colour, clicked_button ? FrameFlag::Lowered : FrameFlags{});
  if (!str.empty()) {
    text = text.CentreToHeight(GetCharacterHeight(FS_NORMAL)).Shrink(WidgetDimensions::scaled.dropdowntext, RectPadding::zero);
    DrawString(text, str, TC_BLACK, align);
  }
 
  Rect button = r.WithWidth(NWidgetLeaf::dropdown_dimension.width, !rtl);
  DrawImageButtons(button, WWT_DROPDOWN, colour, clicked_dropdown, SPR_ARROW_DOWN, SA_CENTER);
}

void Window::DrawWidgets() const
{
  this->nested_root->Draw(this);
 
  if (this->flags.Test(WindowFlag::WhiteBorder)) {
    DrawFrameRect(0, 0, this->width - 1, this->height - 1, COLOUR_WHITE, FrameFlag::BorderOnly);
  }
 
  if (this->flags.Test(WindowFlag::Highlighted)) {
    extern bool _window_highlight_colour;
    for (const auto &pair : this->widget_lookup) {
      const NWidgetBase *widget = pair.second;
      if (!widget->IsHighlighted()) continue;
 
      Rect outer = widget->GetCurrentRect();
      Rect inner = outer.Shrink(WidgetDimensions::scaled.bevel).Expand(1);
 
      PixelColour colour = _string_colourmap[_window_highlight_colour ? widget->GetHighlightColour() : TC_WHITE];
 
      GfxFillRect(outer.left,     outer.top,    inner.left,      inner.bottom, colour);
      GfxFillRect(inner.left + 1, outer.top,    inner.right - 1, inner.top,    colour);
      GfxFillRect(inner.right,    outer.top,    outer.right,     inner.bottom, colour);
      GfxFillRect(outer.left + 1, inner.bottom, outer.right - 1, outer.bottom, colour);
    }
  }
}

void Window::DrawSortButtonState(WidgetID widget, SortButtonState state) const
{
  if (state == SBS_OFF) return;
 
  assert(!this->widget_lookup.empty());
  Rect r = this->GetWidget<NWidgetBase>(widget)->GetCurrentRect();
 
  /* Sort button uses the same sprites as vertical scrollbar */
  Dimension dim = NWidgetScrollbar::GetVerticalDimension();
 
  DrawSpriteIgnorePadding(state == SBS_DOWN ? SPR_ARROW_DOWN : SPR_ARROW_UP, PAL_NONE, r.WithWidth(dim.width, _current_text_dir == TD_LTR), SA_CENTER);
}

int Window::SortButtonWidth()
{
  return NWidgetScrollbar::GetVerticalDimension().width + 1;
}
 
bool _draw_widget_outlines;
 
static void DrawOutline(const Window *, const NWidgetBase *wid)
{
  if (!_draw_widget_outlines || wid->current_x == 0 || wid->current_y == 0) return;
 
  DrawRectOutline(wid->GetCurrentRect(), PC_WHITE, 1, 4);
}




void NWidgetBase::FillWidgetLookup(WidgetLookup &widget_lookup)
{
  if (this->index >= 0) widget_lookup[this->index] = this;
}


void NWidgetBase::SetDirty(const Window *w) const
{
  int abs_left = w->left + this->pos_x;
  int abs_top = w->top + this->pos_y;
  AddDirtyBlock(abs_left, abs_top, abs_left + this->current_x, abs_top + this->current_y);
}


NWidgetBase *NWidgetBase::GetWidgetOfType(WidgetType tp)
{
  return (this->type == tp) ? this : nullptr;
}
 
void NWidgetBase::ApplyAspectRatio()
{
  if (this->aspect_ratio == 0) return;
  if (this->smallest_x == 0 || this->smallest_y == 0) return;
 
  uint x = this->smallest_x;
  uint y = this->smallest_y;
  if (this->aspect_flags.Test(AspectFlag::ResizeX)) x = std::max(this->smallest_x, static_cast<uint>(this->smallest_y * std::abs(this->aspect_ratio)));
  if (this->aspect_flags.Test(AspectFlag::ResizeY)) y = std::max(this->smallest_y, static_cast<uint>(this->smallest_x / std::abs(this->aspect_ratio)));
 
  this->smallest_x = x;
  this->smallest_y = y;
}
 
void NWidgetBase::AdjustPaddingForZoom()
{
  this->padding = ScaleGUITrad(this->uz_padding);
}

NWidgetResizeBase::NWidgetResizeBase(WidgetType tp, WidgetID index, uint fill_x, uint fill_y) : NWidgetBase(tp, index)
{
  this->fill_x = fill_x;
  this->fill_y = fill_y;
}

void NWidgetResizeBase::SetAspect(float ratio, AspectFlags flags)
{
  this->aspect_ratio = ratio;
  this->aspect_flags = flags;
}

void NWidgetResizeBase::SetAspect(int x_ratio, int y_ratio, AspectFlags flags)
{
  this->SetAspect(static_cast<float>(x_ratio) / static_cast<float>(y_ratio), flags);
}
 
void NWidgetResizeBase::AdjustPaddingForZoom()
{
  if (!this->absolute) {
    this->min_x = ScaleGUITrad(this->uz_min_x);
    this->min_y = std::max(ScaleGUITrad(this->uz_min_y), this->uz_text_lines * GetCharacterHeight(this->uz_text_size) + ScaleGUITrad(this->uz_text_spacing));
  }
  NWidgetBase::AdjustPaddingForZoom();
}

void NWidgetResizeBase::SetMinimalSize(uint min_x, uint min_y)
{
  this->uz_min_x = std::max(this->uz_min_x, min_x);
  this->uz_min_y = std::max(this->uz_min_y, min_y);
  this->min_x = ScaleGUITrad(this->uz_min_x);
  this->min_y = std::max(ScaleGUITrad(this->uz_min_y), this->uz_text_lines * GetCharacterHeight(this->uz_text_size) + ScaleGUITrad(this->uz_text_spacing));
}

void NWidgetResizeBase::SetMinimalSizeAbsolute(uint min_x, uint min_y)
{
  this->absolute = true;
  this->min_x = std::max(this->min_x, min_x);
  this->min_y = std::max(this->min_y, min_y);
}

void NWidgetResizeBase::SetMinimalTextLines(uint8_t min_lines, uint8_t spacing, FontSize size)
{
  this->uz_text_lines = min_lines;
  this->uz_text_spacing = spacing;
  this->uz_text_size = size;
  this->min_y = std::max(ScaleGUITrad(this->uz_min_y), this->uz_text_lines * GetCharacterHeight(this->uz_text_size) + ScaleGUITrad(this->uz_text_spacing));
}

void NWidgetResizeBase::SetFill(uint fill_x, uint fill_y)
{
  this->fill_x = fill_x;
  this->fill_y = fill_y;
}

void NWidgetResizeBase::SetResize(uint resize_x, uint resize_y)
{
  this->resize_x = resize_x;
  this->resize_y = resize_y;
}

bool NWidgetResizeBase::UpdateMultilineWidgetSize(const std::string &str, int max_lines)
{
  int y = GetStringHeight(str, this->current_x);
  if (y > max_lines * GetCharacterHeight(FS_NORMAL)) {
    /* Text at the current width is too tall, so try to guess a better width. */
    Dimension d = GetStringBoundingBox(str);
    d.height *= max_lines;
    d.width /= 2;
    return this->UpdateSize(d.width, d.height);
  }
  return this->UpdateVerticalSize(y);
}

bool NWidgetResizeBase::UpdateSize(uint min_x, uint min_y)
{
  if (min_x == this->min_x && min_y == this->min_y) return false;
  this->min_x = min_x;
  this->min_y = min_y;
  return true;
}

bool NWidgetResizeBase::UpdateVerticalSize(uint min_y)
{
  if (min_y == this->min_y) return false;
  this->min_y = min_y;
  return true;
}
 
void NWidgetResizeBase::AssignSizePosition(SizingType sizing, int x, int y, uint given_width, uint given_height, bool)
{
  this->StoreSizePosition(sizing, x, y, given_width, given_height);
}

NWidgetCore::NWidgetCore(WidgetType tp, Colours colour, WidgetID index, uint fill_x, uint fill_y, const WidgetData &widget_data, StringID tool_tip) : NWidgetResizeBase(tp, index, fill_x, fill_y)
{
  this->colour = colour;
  this->widget_data = widget_data;
  this->SetToolTip(tool_tip);
  this->text_colour = tp == WWT_CAPTION ? TC_WHITE : TC_BLACK;
}

void NWidgetCore::SetString(StringID string)
{
  this->widget_data.string = string;
}

void NWidgetCore::SetStringTip(StringID string, StringID tool_tip)
{
  this->SetString(string);
  this->SetToolTip(tool_tip);
}

void NWidgetCore::SetSprite(SpriteID sprite)
{
  this->widget_data.sprite = sprite;
}

void NWidgetCore::SetSpriteTip(SpriteID sprite, StringID tool_tip)
{
  this->SetSprite(sprite);
  this->SetToolTip(tool_tip);
}

void NWidgetCore::SetMatrixDimension(uint32_t columns, uint32_t rows)
{
  this->widget_data.matrix = { columns, rows };
}

void NWidgetCore::SetResizeWidgetType(ResizeWidgetValues type)
{
  this->widget_data.resize_widget_type = type;
}

void NWidgetCore::SetTextStyle(TextColour colour, FontSize size)
{
  this->text_colour = colour;
  this->text_size = size;
}

void NWidgetCore::SetToolTip(StringID tool_tip)
{
  this->tool_tip = tool_tip;
}

StringID NWidgetCore::GetToolTip() const
{
  return this->tool_tip;
}

void NWidgetCore::SetAlignment(StringAlignment align)
{
  this->align = align;
}

StringID NWidgetCore::GetString() const
{
  return this->widget_data.string;
}

WidgetID NWidgetCore::GetScrollbarIndex() const
{
  return this->scrollbar_index;
}
 
NWidgetCore *NWidgetCore::GetWidgetFromPos(int x, int y)
{
  return (IsInsideBS(x, this->pos_x, this->current_x) && IsInsideBS(y, this->pos_y, this->current_y)) ? this : nullptr;
}
 
NWidgetBase *NWidgetContainer::GetWidgetOfType(WidgetType tp)
{
  if (this->type == tp) return this;
  for (const auto &child_wid : this->children) {
    NWidgetBase *nwid = child_wid->GetWidgetOfType(tp);
    if (nwid != nullptr) return nwid;
  }
  return nullptr;
}
 
void NWidgetContainer::AdjustPaddingForZoom()
{
  for (const auto &child_wid : this->children) {
    child_wid->AdjustPaddingForZoom();
  }
  NWidgetBase::AdjustPaddingForZoom();
}

void NWidgetContainer::Add(std::unique_ptr<NWidgetBase> &&wid)
{
  assert(wid != nullptr);
  wid->parent = this;
  this->children.push_back(std::move(wid));
}
 
void NWidgetContainer::FillWidgetLookup(WidgetLookup &widget_lookup)
{
  this->NWidgetBase::FillWidgetLookup(widget_lookup);
  for (const auto &child_wid : this->children) {
    child_wid->FillWidgetLookup(widget_lookup);
  }
}
 
void NWidgetContainer::Draw(const Window *w)
{
  for (const auto &child_wid : this->children) {
    child_wid->Draw(w);
  }
 
  DrawOutline(w, this);
}
 
NWidgetCore *NWidgetContainer::GetWidgetFromPos(int x, int y)
{
  if (!IsInsideBS(x, this->pos_x, this->current_x) || !IsInsideBS(y, this->pos_y, this->current_y)) return nullptr;
 
  for (const auto &child_wid : this->children) {
    NWidgetCore *nwid = child_wid->GetWidgetFromPos(x, y);
    if (nwid != nullptr) return nwid;
  }
  return nullptr;
}
 
void NWidgetStacked::SetupSmallestSize(Window *w)
{
  /* Zero size plane selected */
  if (this->shown_plane >= SZSP_BEGIN) {
    Dimension size    = {0, 0};
    Dimension padding = {0, 0};
    Dimension fill    = {(this->shown_plane == SZSP_HORIZONTAL), (this->shown_plane == SZSP_VERTICAL)};
    Dimension resize  = {(this->shown_plane == SZSP_HORIZONTAL), (this->shown_plane == SZSP_VERTICAL)};
    /* Here we're primarily interested in the value of resize */
    if (this->index >= 0) w->UpdateWidgetSize(this->index, size, padding, fill, resize);
 
    this->smallest_x = size.width;
    this->smallest_y = size.height;
    this->fill_x = fill.width;
    this->fill_y = fill.height;
    this->resize_x = resize.width;
    this->resize_y = resize.height;
    this->ApplyAspectRatio();
    return;
  }
 
  /* First sweep, recurse down and compute minimal size and filling. */
  this->smallest_x = 0;
  this->smallest_y = 0;
  this->fill_x = this->IsEmpty() ? 0 : 1;
  this->fill_y = this->IsEmpty() ? 0 : 1;
  this->resize_x = this->IsEmpty() ? 0 : 1;
  this->resize_y = this->IsEmpty() ? 0 : 1;
  for (const auto &child_wid : this->children) {
    child_wid->SetupSmallestSize(w);
 
    this->smallest_x = std::max(this->smallest_x, child_wid->smallest_x + child_wid->padding.Horizontal());
    this->smallest_y = std::max(this->smallest_y, child_wid->smallest_y + child_wid->padding.Vertical());
    this->fill_x = std::lcm(this->fill_x, child_wid->fill_x);
    this->fill_y = std::lcm(this->fill_y, child_wid->fill_y);
    this->resize_x = std::lcm(this->resize_x, child_wid->resize_x);
    this->resize_y = std::lcm(this->resize_y, child_wid->resize_y);
    this->ApplyAspectRatio();
  }
}
 
void NWidgetStacked::AssignSizePosition(SizingType sizing, int x, int y, uint given_width, uint given_height, bool rtl)
{
  assert(given_width >= this->smallest_x && given_height >= this->smallest_y);
  this->StoreSizePosition(sizing, x, y, given_width, given_height);
 
  if (this->shown_plane >= SZSP_BEGIN) return;
 
  for (const auto &child_wid : this->children) {
    uint hor_step = (sizing == ST_SMALLEST) ? 1 : child_wid->GetHorizontalStepSize(sizing);
    uint child_width = ComputeMaxSize(child_wid->smallest_x, given_width - child_wid->padding.Horizontal(), hor_step);
    uint child_pos_x = (rtl ? child_wid->padding.right : child_wid->padding.left);
 
    uint vert_step = (sizing == ST_SMALLEST) ? 1 : child_wid->GetVerticalStepSize(sizing);
    uint child_height = ComputeMaxSize(child_wid->smallest_y, given_height - child_wid->padding.Vertical(), vert_step);
    uint child_pos_y = child_wid->padding.top;
 
    child_wid->AssignSizePosition(sizing, x + child_pos_x, y + child_pos_y, child_width, child_height, rtl);
  }
}
 
void NWidgetStacked::FillWidgetLookup(WidgetLookup &widget_lookup)
{
  /* We need to update widget_lookup later. */
  this->widget_lookup = &widget_lookup;
 
  this->NWidgetContainer::FillWidgetLookup(widget_lookup);
  /* In case widget IDs are repeated, make sure Window::GetWidget works on displayed widgets. */
  if (static_cast<size_t>(this->shown_plane) < this->children.size()) this->children[shown_plane]->FillWidgetLookup(widget_lookup);
}
 
void NWidgetStacked::Draw(const Window *w)
{
  if (this->shown_plane >= SZSP_BEGIN) return;
 
  assert(static_cast<size_t>(this->shown_plane) < this->children.size());
  this->children[shown_plane]->Draw(w);
  DrawOutline(w, this);
}
 
NWidgetCore *NWidgetStacked::GetWidgetFromPos(int x, int y)
{
  if (this->shown_plane >= SZSP_BEGIN) return nullptr;
 
  if (!IsInsideBS(x, this->pos_x, this->current_x) || !IsInsideBS(y, this->pos_y, this->current_y)) return nullptr;
 
  if (static_cast<size_t>(this->shown_plane) >= this->children.size()) return nullptr;
  return this->children[shown_plane]->GetWidgetFromPos(x, y);
}

bool NWidgetStacked::SetDisplayedPlane(int plane)
{
  if (this->shown_plane == plane) return false;
  this->shown_plane = plane;
  /* In case widget IDs are repeated, make sure Window::GetWidget works on displayed widgets. */
  if (static_cast<size_t>(this->shown_plane) < this->children.size()) this->children[shown_plane]->FillWidgetLookup(*this->widget_lookup);
  return true;
}
 
class NWidgetLayer : public NWidgetContainer {
public:
  NWidgetLayer(WidgetID index) : NWidgetContainer(NWID_LAYER, index) {}
 
  void SetupSmallestSize(Window *w) override;
  void AssignSizePosition(SizingType sizing, int x, int y, uint given_width, uint given_height, bool rtl) override;
 
  void Draw(const Window *w) override;
};
 
void NWidgetLayer::SetupSmallestSize(Window *w)
{
  /* First sweep, recurse down and compute minimal size and filling. */
  this->smallest_x = 0;
  this->smallest_y = 0;
  this->fill_x = this->IsEmpty() ? 0 : 1;
  this->fill_y = this->IsEmpty() ? 0 : 1;
  this->resize_x = this->IsEmpty() ? 0 : 1;
  this->resize_y = this->IsEmpty() ? 0 : 1;
  for (const auto &child_wid : this->children) {
    child_wid->SetupSmallestSize(w);
 
    this->smallest_x = std::max(this->smallest_x, child_wid->smallest_x + child_wid->padding.Horizontal());
    this->smallest_y = std::max(this->smallest_y, child_wid->smallest_y + child_wid->padding.Vertical());
    this->fill_x = std::lcm(this->fill_x, child_wid->fill_x);
    this->fill_y = std::lcm(this->fill_y, child_wid->fill_y);
    this->resize_x = std::lcm(this->resize_x, child_wid->resize_x);
    this->resize_y = std::lcm(this->resize_y, child_wid->resize_y);
    this->ApplyAspectRatio();
  }
}
 
void NWidgetLayer::AssignSizePosition(SizingType sizing, int x, int y, uint given_width, uint given_height, bool rtl)
{
  assert(given_width >= this->smallest_x && given_height >= this->smallest_y);
  this->StoreSizePosition(sizing, x, y, given_width, given_height);
 
  for (const auto &child_wid : this->children) {
    uint hor_step = (sizing == ST_SMALLEST) ? 1 : child_wid->GetHorizontalStepSize(sizing);
    uint child_width = ComputeMaxSize(child_wid->smallest_x, given_width - child_wid->padding.Horizontal(), hor_step);
    uint child_pos_x = (rtl ? child_wid->padding.right : child_wid->padding.left);
 
    uint vert_step = (sizing == ST_SMALLEST) ? 1 : child_wid->GetVerticalStepSize(sizing);
    uint child_height = ComputeMaxSize(child_wid->smallest_y, given_height - child_wid->padding.Vertical(), vert_step);
    uint child_pos_y = child_wid->padding.top;
 
    child_wid->AssignSizePosition(sizing, x + child_pos_x, y + child_pos_y, child_width, child_height, rtl);
  }
}
 
void NWidgetLayer::Draw(const Window *w)
{
  /* Draw in reverse order, as layers are arranged top-down. */
  for (auto it = std::rbegin(this->children); it != std::rend(this->children); ++it) {
    (*it)->Draw(w);
  }
 
  DrawOutline(w, this);
}
 
void NWidgetPIPContainer::AdjustPaddingForZoom()
{
  this->pip_pre = ScaleGUITrad(this->uz_pip_pre);
  this->pip_inter = ScaleGUITrad(this->uz_pip_inter);
  this->pip_post = ScaleGUITrad(this->uz_pip_post);
  NWidgetContainer::AdjustPaddingForZoom();
}

void NWidgetPIPContainer::SetPIP(uint8_t pip_pre, uint8_t pip_inter, uint8_t pip_post)
{
  this->uz_pip_pre = pip_pre;
  this->uz_pip_inter = pip_inter;
  this->uz_pip_post = pip_post;
 
  this->pip_pre = ScaleGUITrad(this->uz_pip_pre);
  this->pip_inter = ScaleGUITrad(this->uz_pip_inter);
  this->pip_post = ScaleGUITrad(this->uz_pip_post);
}

void NWidgetPIPContainer::SetPIPRatio(uint8_t pip_ratio_pre, uint8_t pip_ratio_inter, uint8_t pip_ratio_post)
{
  this->pip_ratio_pre = pip_ratio_pre;
  this->pip_ratio_inter = pip_ratio_inter;
  this->pip_ratio_post = pip_ratio_post;
}
 
void NWidgetHorizontal::SetupSmallestSize(Window *w)
{
  this->smallest_x = 0; // Sum of minimal size of all children.
  this->smallest_y = 0; // Biggest child.
  this->fill_x = 0;     // smallest non-zero child widget fill step.
  this->fill_y = 1;     // smallest common child fill step.
  this->resize_x = 0;   // smallest non-zero child widget resize step.
  this->resize_y = 1;   // smallest common child resize step.
  this->gaps = 0;
 
  /* 1a. Forward call, collect longest/widest child length. */
  uint longest = 0; // Longest child found.
  uint max_vert_fill = 0; // Biggest vertical fill step.
  for (const auto &child_wid : this->children) {
    child_wid->SetupSmallestSize(w);
    longest = std::max(longest, child_wid->smallest_x);
    max_vert_fill = std::max(max_vert_fill, child_wid->GetVerticalStepSize(ST_SMALLEST));
    this->smallest_y = std::max(this->smallest_y, child_wid->smallest_y + child_wid->padding.Vertical());
    if (child_wid->smallest_x != 0 || child_wid->fill_x != 0) this->gaps++;
  }
  if (this->gaps > 0) this->gaps--; // Number of gaps is number of widgets less one.
  /* 1b. Make the container higher if needed to accommodate all children nicely. */
  [[maybe_unused]] uint max_smallest = this->smallest_y + 3 * max_vert_fill; // Upper limit to computing smallest height.
  uint cur_height = this->smallest_y;
  for (;;) {
    for (const auto &child_wid : this->children) {
      uint step_size = child_wid->GetVerticalStepSize(ST_SMALLEST);
      uint child_height = child_wid->smallest_y + child_wid->padding.Vertical();
      if (step_size > 1 && child_height < cur_height) { // Small step sizes or already fitting children are not interesting.
        uint remainder = (cur_height - child_height) % step_size;
        if (remainder > 0) { // Child did not fit entirely, widen the container.
          cur_height += step_size - remainder;
          assert(cur_height < max_smallest); // Safeguard against infinite height expansion.
          /* Remaining children will adapt to the new cur_height, thus speeding up the computation. */
        }
      }
    }
    if (this->smallest_y == cur_height) break;
    this->smallest_y = cur_height; // Smallest height got changed, try again.
  }
  /* 2. For containers that must maintain equal width, extend child minimal size. */
  for (const auto &child_wid : this->children) {
    child_wid->smallest_y = this->smallest_y - child_wid->padding.Vertical();
    child_wid->ApplyAspectRatio();
    longest = std::max(longest, child_wid->smallest_x);
  }
  if (this->flags.Test(NWidContainerFlag::EqualSize)) {
    for (const auto &child_wid : this->children) {
      if (child_wid->fill_x == 1) child_wid->smallest_x = longest;
    }
  }
  /* 3. Compute smallest, fill, and resize values of the container. */
  for (const auto &child_wid : this->children) {
    this->smallest_x += child_wid->smallest_x + child_wid->padding.Horizontal();
    if (child_wid->fill_x > 0) {
      if (this->fill_x == 0 || this->fill_x > child_wid->fill_x) this->fill_x = child_wid->fill_x;
    }
    this->fill_y = std::lcm(this->fill_y, child_wid->fill_y);
 
    if (child_wid->resize_x > 0) {
      if (this->resize_x == 0 || this->resize_x > child_wid->resize_x) this->resize_x = child_wid->resize_x;
    }
    this->resize_y = std::lcm(this->resize_y, child_wid->resize_y);
  }
  if (this->fill_x == 0 && this->pip_ratio_pre + this->pip_ratio_inter + this->pip_ratio_post > 0) this->fill_x = 1;
  /* 4. Increase by required PIP space. */
  this->smallest_x += this->pip_pre + this->gaps * this->pip_inter + this->pip_post;
}
 
void NWidgetHorizontal::AssignSizePosition(SizingType sizing, int x, int y, uint given_width, uint given_height, bool rtl)
{
  assert(given_width >= this->smallest_x && given_height >= this->smallest_y);
 
  /* Compute additional width given to us. */
  uint additional_length = given_width - (this->pip_pre + this->gaps * this->pip_inter + this->pip_post);
  for (const auto &child_wid : this->children) {
    if (child_wid->smallest_x != 0 || child_wid->fill_x != 0) additional_length -= child_wid->smallest_x + child_wid->padding.Horizontal();
  }
 
  this->StoreSizePosition(sizing, x, y, given_width, given_height);
 
  /* In principle, the additional horizontal space is distributed evenly over the available resizable children. Due to step sizes, this may not always be feasible.
   * To make resizing work as good as possible, first children with biggest step sizes are done. These may get less due to rounding down.
   * This additional space is then given to children with smaller step sizes. This will give a good result when resize steps of each child is a multiple
   * of the child with the smallest non-zero stepsize.
   *
   * Since child sizes are computed out of order, positions cannot be calculated until all sizes are known. That means it is not possible to compute the child
   * size and position, and directly call child->AssignSizePosition() with the computed values.
   * Instead, computed child widths and heights are stored in child->current_x and child->current_y values. That is allowed, since this method overwrites those values
   * then we call the child.
   */
 
  /* First loop: Find biggest stepsize, find number of children that want a piece of the pie, handle vertical size for all children,
   * handle horizontal size for non-resizing children.
   */
  int num_changing_childs = 0; // Number of children that can change size.
  uint biggest_stepsize = 0;
  for (const auto &child_wid : this->children) {
    uint hor_step = child_wid->GetHorizontalStepSize(sizing);
    if (hor_step > 0) {
      if (!flags.Test(NWidContainerFlag::BigFirst)) num_changing_childs++;
      biggest_stepsize = std::max(biggest_stepsize, hor_step);
    } else {
      child_wid->current_x = child_wid->smallest_x;
    }
 
    uint vert_step = (sizing == ST_SMALLEST) ? 1 : child_wid->GetVerticalStepSize(sizing);
    child_wid->current_y = ComputeMaxSize(child_wid->smallest_y, given_height - child_wid->padding.Vertical(), vert_step);
  }
 
  /* First.5 loop: count how many children are of the biggest step size. */
  if (flags.Test(NWidContainerFlag::BigFirst) && biggest_stepsize > 0) {
    for (const auto &child_wid : this->children) {
      uint hor_step = child_wid->GetHorizontalStepSize(sizing);
      if (hor_step == biggest_stepsize) {
        num_changing_childs++;
      }
    }
  }
 
  /* Second loop: Allocate the additional horizontal space over the resizing children, starting with the biggest resize steps. */
  while (biggest_stepsize > 0) {
    uint next_biggest_stepsize = 0;
    for (const auto &child_wid : this->children) {
      uint hor_step = child_wid->GetHorizontalStepSize(sizing);
      if (hor_step > biggest_stepsize) continue; // Already done
      if (hor_step == biggest_stepsize) {
        uint increment = additional_length / num_changing_childs;
        num_changing_childs--;
        if (hor_step > 1) increment -= increment % hor_step;
        child_wid->current_x = child_wid->smallest_x + increment;
        additional_length -= increment;
        continue;
      }
      next_biggest_stepsize = std::max(next_biggest_stepsize, hor_step);
    }
    biggest_stepsize = next_biggest_stepsize;
 
    if (num_changing_childs == 0 && flags.Test(NWidContainerFlag::BigFirst) && biggest_stepsize > 0) {
      /* Second.5 loop: count how many children are of the updated biggest step size. */
      for (const auto &child_wid : this->children) {
        uint hor_step = child_wid->GetHorizontalStepSize(sizing);
        if (hor_step == biggest_stepsize) {
          num_changing_childs++;
        }
      }
    }
  }
  assert(num_changing_childs == 0);
 
  uint pre = this->pip_pre;
  uint inter = this->pip_inter;
 
  if (additional_length > 0) {
    /* Allocate remaining space by pip ratios. If this doesn't round exactly, the unused space will fall into pip_post
     * which is never explicitly needed. */
    int r = this->pip_ratio_pre + this->gaps * this->pip_ratio_inter + this->pip_ratio_post;
    if (r > 0) {
      pre += this->pip_ratio_pre * additional_length / r;
      if (this->gaps > 0) inter += this->pip_ratio_inter * additional_length / r;
    }
  }
 
  /* Third loop: Compute position and call the child. */
  uint position = rtl ? this->current_x - pre : pre; // Place to put next child relative to origin of the container.
  for (const auto &child_wid : this->children) {
    uint child_width = child_wid->current_x;
    uint child_x = x + (rtl ? position - child_width - child_wid->padding.left : position + child_wid->padding.left);
    uint child_y = y + child_wid->padding.top;
 
    child_wid->AssignSizePosition(sizing, child_x, child_y, child_width, child_wid->current_y, rtl);
    if (child_wid->current_x != 0) {
      uint padded_child_width = child_width + child_wid->padding.Horizontal() + inter;
      position = rtl ? position - padded_child_width : position + padded_child_width;
    }
  }
}
 
void NWidgetHorizontalLTR::AssignSizePosition(SizingType sizing, int x, int y, uint given_width, uint given_height, bool)
{
  NWidgetHorizontal::AssignSizePosition(sizing, x, y, given_width, given_height, false);
}
 
void NWidgetVertical::SetupSmallestSize(Window *w)
{
  this->smallest_x = 0; // Biggest child.
  this->smallest_y = 0; // Sum of minimal size of all children.
  this->fill_x = 1;     // smallest common child fill step.
  this->fill_y = 0;     // smallest non-zero child widget fill step.
  this->resize_x = 1;   // smallest common child resize step.
  this->resize_y = 0;   // smallest non-zero child widget resize step.
  this->gaps = 0;
 
  /* 1a. Forward call, collect longest/widest child length. */
  uint highest = 0; // Highest child found.
  uint max_hor_fill = 0; // Biggest horizontal fill step.
  for (const auto &child_wid : this->children) {
    child_wid->SetupSmallestSize(w);
    highest = std::max(highest, child_wid->smallest_y);
    max_hor_fill = std::max(max_hor_fill, child_wid->GetHorizontalStepSize(ST_SMALLEST));
    this->smallest_x = std::max(this->smallest_x, child_wid->smallest_x + child_wid->padding.Horizontal());
    if (child_wid->smallest_y != 0 || child_wid->fill_y != 0) this->gaps++;
  }
  if (this->gaps > 0) this->gaps--; // Number of gaps is number of widgets less one.
  /* 1b. Make the container wider if needed to accommodate all children nicely. */
  [[maybe_unused]] uint max_smallest = this->smallest_x + 3 * max_hor_fill; // Upper limit to computing smallest height.
  uint cur_width = this->smallest_x;
  for (;;) {
    for (const auto &child_wid : this->children) {
      uint step_size = child_wid->GetHorizontalStepSize(ST_SMALLEST);
      uint child_width = child_wid->smallest_x + child_wid->padding.Horizontal();
      if (step_size > 1 && child_width < cur_width) { // Small step sizes or already fitting children are not interesting.
        uint remainder = (cur_width - child_width) % step_size;
        if (remainder > 0) { // Child did not fit entirely, widen the container.
          cur_width += step_size - remainder;
          assert(cur_width < max_smallest); // Safeguard against infinite width expansion.
          /* Remaining children will adapt to the new cur_width, thus speeding up the computation. */
        }
      }
    }
    if (this->smallest_x == cur_width) break;
    this->smallest_x = cur_width; // Smallest width got changed, try again.
  }
  /* 2. For containers that must maintain equal width, extend children minimal size. */
  for (const auto &child_wid : this->children) {
    child_wid->smallest_x = this->smallest_x - child_wid->padding.Horizontal();
    child_wid->ApplyAspectRatio();
    highest = std::max(highest, child_wid->smallest_y);
  }
  if (this->flags.Test(NWidContainerFlag::EqualSize)) {
    for (const auto &child_wid : this->children) {
      if (child_wid->fill_y == 1) child_wid->smallest_y = highest;
    }
  }
  /* 3. Compute smallest, fill, and resize values of the container. */
  for (const auto &child_wid : this->children) {
    this->smallest_y += child_wid->smallest_y + child_wid->padding.Vertical();
    if (child_wid->fill_y > 0) {
      if (this->fill_y == 0 || this->fill_y > child_wid->fill_y) this->fill_y = child_wid->fill_y;
    }
    this->fill_x = std::lcm(this->fill_x, child_wid->fill_x);
 
    if (child_wid->resize_y > 0) {
      if (this->resize_y == 0 || this->resize_y > child_wid->resize_y) this->resize_y = child_wid->resize_y;
    }
    this->resize_x = std::lcm(this->resize_x, child_wid->resize_x);
  }
  if (this->fill_y == 0 && this->pip_ratio_pre + this->pip_ratio_inter + this->pip_ratio_post > 0) this->fill_y = 1;
  /* 4. Increase by required PIP space. */
  this->smallest_y += this->pip_pre + this->gaps * this->pip_inter + this->pip_post;
}
 
void NWidgetVertical::AssignSizePosition(SizingType sizing, int x, int y, uint given_width, uint given_height, bool rtl)
{
  assert(given_width >= this->smallest_x && given_height >= this->smallest_y);
 
  /* Compute additional height given to us. */
  uint additional_length = given_height - (this->pip_pre + this->gaps * this->pip_inter + this->pip_post);
  for (const auto &child_wid : this->children) {
    if (child_wid->smallest_y != 0 || child_wid->fill_y != 0) additional_length -= child_wid->smallest_y + child_wid->padding.Vertical();
  }
 
  this->StoreSizePosition(sizing, x, y, given_width, given_height);
 
  /* Like the horizontal container, the vertical container also distributes additional height evenly, starting with the children with the biggest resize steps.
   * It also stores computed widths and heights into current_x and current_y values of the child.
   */
 
  /* First loop: Find biggest stepsize, find number of children that want a piece of the pie, handle horizontal size for all children, handle vertical size for non-resizing child. */
  int num_changing_childs = 0; // Number of children that can change size.
  uint biggest_stepsize = 0;
  for (const auto &child_wid : this->children) {
    uint vert_step = child_wid->GetVerticalStepSize(sizing);
    if (vert_step > 0) {
      if (!flags.Test(NWidContainerFlag::BigFirst)) num_changing_childs++;
      biggest_stepsize = std::max(biggest_stepsize, vert_step);
    } else {
      child_wid->current_y = child_wid->smallest_y;
    }
 
    uint hor_step = (sizing == ST_SMALLEST) ? 1 : child_wid->GetHorizontalStepSize(sizing);
    child_wid->current_x = ComputeMaxSize(child_wid->smallest_x, given_width - child_wid->padding.Horizontal(), hor_step);
  }
 
  /* First.5 loop: count how many children are of the biggest step size. */
  if (this->flags.Test(NWidContainerFlag::BigFirst) && biggest_stepsize > 0) {
    for (const auto &child_wid : this->children) {
      uint vert_step = child_wid->GetVerticalStepSize(sizing);
      if (vert_step == biggest_stepsize) {
        num_changing_childs++;
      }
    }
  }
 
  /* Second loop: Allocate the additional vertical space over the resizing children, starting with the biggest resize steps. */
  while (biggest_stepsize > 0) {
    uint next_biggest_stepsize = 0;
    for (const auto &child_wid : this->children) {
      uint vert_step = child_wid->GetVerticalStepSize(sizing);
      if (vert_step > biggest_stepsize) continue; // Already done
      if (vert_step == biggest_stepsize) {
        uint increment = additional_length / num_changing_childs;
        num_changing_childs--;
        if (vert_step > 1) increment -= increment % vert_step;
        child_wid->current_y = child_wid->smallest_y + increment;
        additional_length -= increment;
        continue;
      }
      next_biggest_stepsize = std::max(next_biggest_stepsize, vert_step);
    }
    biggest_stepsize = next_biggest_stepsize;
 
    if (num_changing_childs == 0 && flags.Test(NWidContainerFlag::BigFirst) && biggest_stepsize > 0) {
      /* Second.5 loop: count how many children are of the updated biggest step size. */
      for (const auto &child_wid : this->children) {
        uint vert_step = child_wid->GetVerticalStepSize(sizing);
        if (vert_step == biggest_stepsize) {
          num_changing_childs++;
        }
      }
    }
  }
  assert(num_changing_childs == 0);
 
  uint pre = this->pip_pre;
  uint inter = this->pip_inter;
 
  if (additional_length > 0) {
    /* Allocate remaining space by pip ratios. If this doesn't round exactly, the unused space will fall into pip_post
     * which is never explicitly needed. */
    int r = this->pip_ratio_pre + this->gaps * this->pip_ratio_inter + this->pip_ratio_post;
    if (r > 0) {
      pre += this->pip_ratio_pre * additional_length / r;
      if (this->gaps > 0) inter += this->pip_ratio_inter * additional_length / r;
    }
  }
 
  /* Third loop: Compute position and call the child. */
  uint position = pre; // Place to put next child relative to origin of the container.
  for (const auto &child_wid : this->children) {
    uint child_x = x + (rtl ? child_wid->padding.right : child_wid->padding.left);
    uint child_height = child_wid->current_y;
 
    child_wid->AssignSizePosition(sizing, child_x, y + position + child_wid->padding.top, child_wid->current_x, child_height, rtl);
    if (child_wid->current_y != 0) {
      position += child_height + child_wid->padding.Vertical() + inter;
    }
  }
}

NWidgetSpacer::NWidgetSpacer(int width, int height) : NWidgetResizeBase(NWID_SPACER, INVALID_WIDGET, 0, 0)
{
  this->SetMinimalSize(width, height);
  this->SetResize(0, 0);
}
 
void NWidgetSpacer::SetupSmallestSize(Window *)
{
  this->smallest_x = this->min_x;
  this->smallest_y = this->min_y;
  this->ApplyAspectRatio();
}
 
void NWidgetSpacer::Draw(const Window *w)
{
  /* Spacer widget is never normally visible. */
 
  if (_draw_widget_outlines && this->current_x != 0 && this->current_y != 0) {
    /* Spacers indicate a potential design issue, so get extra highlighting. */
    GfxFillRect(this->GetCurrentRect(), PC_WHITE, FILLRECT_CHECKER);
 
    DrawOutline(w, this);
  }
}
 
void NWidgetSpacer::SetDirty(const Window *) const
{
  /* Spacer widget never need repainting. */
}
 
NWidgetCore *NWidgetSpacer::GetWidgetFromPos(int, int)
{
  return nullptr;
}

void NWidgetMatrix::SetClicked(int clicked)
{
  this->clicked = clicked;
  if (this->clicked >= 0 && this->sb != nullptr && this->widgets_x != 0) {
    int vpos = (this->clicked / this->widgets_x) * this->widget_h; // Vertical position of the top.
    /* Need to scroll down -> Scroll to the bottom.
     * However, last entry has no 'this->pip_inter' underneath, and we must stay below this->sb->GetCount() */
    if (this->sb->GetPosition() < vpos) vpos += this->widget_h - this->pip_inter - 1;
    this->sb->ScrollTowards(vpos);
  }
}

void NWidgetMatrix::SetCount(int count)
{
  this->count = count;
 
  if (this->sb == nullptr || this->widgets_x == 0) return;
 
  /* We need to get the number of pixels the matrix is high/wide.
   * So, determine the number of rows/columns based on the number of
   * columns/rows (one is constant/unscrollable).
   * Then multiply that by the height of a widget, and add the pre
   * and post spacing "offsets". */
  count = CeilDiv(count, this->sb->IsVertical() ? this->widgets_x : this->widgets_y);
  count *= (this->sb->IsVertical() ? this->children.front()->smallest_y : this->children.front()->smallest_x) + this->pip_inter;
  if (count > 0) count -= this->pip_inter; // We counted an inter too much in the multiplication above
  count += this->pip_pre + this->pip_post;
  this->sb->SetCount(count);
  this->sb->SetCapacity(this->sb->IsVertical() ? this->current_y : this->current_x);
  this->sb->SetStepSize(this->sb->IsVertical() ? this->widget_h  : this->widget_w);
}

void NWidgetMatrix::SetScrollbar(Scrollbar *sb)
{
  this->sb = sb;
}

int NWidgetMatrix::GetCurrentElement() const
{
  return this->current_element;
}
 
void NWidgetMatrix::SetupSmallestSize(Window *w)
{
  assert(this->children.size() == 1);
 
  this->children.front()->SetupSmallestSize(w);
 
  Dimension padding = { (uint)this->pip_pre + this->pip_post, (uint)this->pip_pre + this->pip_post};
  Dimension size    = {this->children.front()->smallest_x + padding.width, this->children.front()->smallest_y + padding.height};
  Dimension fill    = {0, 0};
  Dimension resize  = {this->pip_inter + this->children.front()->smallest_x, this->pip_inter + this->children.front()->smallest_y};
 
  if (this->index >= 0) w->UpdateWidgetSize(this->index, size, padding, fill, resize);
 
  this->smallest_x = size.width;
  this->smallest_y = size.height;
  this->fill_x = fill.width;
  this->fill_y = fill.height;
  this->resize_x = resize.width;
  this->resize_y = resize.height;
  this->ApplyAspectRatio();
}
 
void NWidgetMatrix::AssignSizePosition(SizingType, int x, int y, uint given_width, uint given_height, bool)
{
  assert(given_width >= this->smallest_x && given_height >= this->smallest_y);
 
  this->pos_x = x;
  this->pos_y = y;
  this->current_x = given_width;
  this->current_y = given_height;
 
  /* Determine the size of the widgets, and the number of visible widgets on each of the axis. */
  this->widget_w = this->children.front()->smallest_x + this->pip_inter;
  this->widget_h = this->children.front()->smallest_y + this->pip_inter;
 
  /* Account for the pip_inter is between widgets, so we need to account for that when
   * the division assumes pip_inter is used for all widgets. */
  this->widgets_x = CeilDiv(this->current_x - this->pip_pre - this->pip_post + this->pip_inter, this->widget_w);
  this->widgets_y = CeilDiv(this->current_y - this->pip_pre - this->pip_post + this->pip_inter, this->widget_h);
 
  /* When resizing, update the scrollbar's count. E.g. with a vertical
   * scrollbar becoming wider or narrower means the amount of rows in
   * the scrollbar becomes respectively smaller or higher. */
  this->SetCount(this->count);
}
 
NWidgetCore *NWidgetMatrix::GetWidgetFromPos(int x, int y)
{
  /* Falls outside of the matrix widget. */
  if (!IsInsideBS(x, this->pos_x, this->current_x) || !IsInsideBS(y, this->pos_y, this->current_y)) return nullptr;
 
  int start_x, start_y, base_offs_x, base_offs_y;
  this->GetScrollOffsets(start_x, start_y, base_offs_x, base_offs_y);
 
  bool rtl = _current_text_dir == TD_RTL;
 
  int widget_col = (rtl ?
        -x + (int)this->pip_post + this->pos_x + base_offs_x + this->widget_w - 1 - (int)this->pip_inter :
         x - (int)this->pip_pre  - this->pos_x - base_offs_x
      ) / this->widget_w;
 
  int widget_row = (y - base_offs_y - (int)this->pip_pre - this->pos_y) / this->widget_h;
 
  this->current_element = (widget_row + start_y) * this->widgets_x + start_x + widget_col;
  if (this->current_element >= this->count) return nullptr;
 
  NWidgetCore *child = dynamic_cast<NWidgetCore *>(this->children.front().get());
  assert(child != nullptr);
  child->AssignSizePosition(ST_RESIZE,
      this->pos_x + (rtl ? this->pip_post - widget_col * this->widget_w : this->pip_pre + widget_col * this->widget_w) + base_offs_x,
      this->pos_y + this->pip_pre + widget_row * this->widget_h + base_offs_y,
      child->smallest_x, child->smallest_y, rtl);
 
  return child->GetWidgetFromPos(x, y);
}
 
/* virtual */ void NWidgetMatrix::Draw(const Window *w)
{
  /* Fill the background. */
  GfxFillRect(this->GetCurrentRect(), GetColourGradient(this->colour, SHADE_LIGHT));
 
  /* Set up a clipping area for the previews. */
  bool rtl = _current_text_dir == TD_RTL;
  DrawPixelInfo tmp_dpi;
  if (!FillDrawPixelInfo(&tmp_dpi, this->pos_x + (rtl ? this->pip_post : this->pip_pre), this->pos_y + this->pip_pre, this->current_x - this->pip_pre - this->pip_post, this->current_y - this->pip_pre - this->pip_post)) return;
 
  {
    AutoRestoreBackup dpi_backup(_cur_dpi, &tmp_dpi);
 
    /* Get the appropriate offsets so we can draw the right widgets. */
    NWidgetCore *child = dynamic_cast<NWidgetCore *>(this->children.front().get());
    assert(child != nullptr);
    int start_x, start_y, base_offs_x, base_offs_y;
    this->GetScrollOffsets(start_x, start_y, base_offs_x, base_offs_y);
 
    int offs_y = base_offs_y;
    for (int y = start_y; y < start_y + this->widgets_y + 1; y++, offs_y += this->widget_h) {
      /* Are we within bounds? */
      if (offs_y + child->smallest_y <= 0) continue;
      if (offs_y >= (int)this->current_y) break;
 
      /* We've passed our amount of widgets. */
      if (y * this->widgets_x >= this->count) break;
 
      int offs_x = base_offs_x;
      for (int x = start_x; x < start_x + this->widgets_x + 1; x++, offs_x += rtl ? -this->widget_w : this->widget_w) {
        /* Are we within bounds? */
        if (offs_x + child->smallest_x <= 0) continue;
        if (offs_x >= (int)this->current_x) continue;
 
        /* Do we have this many widgets? */
        this->current_element = y * this->widgets_x + x;
        if (this->current_element >= this->count) break;
 
        child->AssignSizePosition(ST_RESIZE, offs_x, offs_y, child->smallest_x, child->smallest_y, rtl);
        child->SetLowered(this->clicked == this->current_element);
        child->Draw(w);
      }
    }
  }
 
  DrawOutline(w, this);
}

void NWidgetMatrix::GetScrollOffsets(int &start_x, int &start_y, int &base_offs_x, int &base_offs_y)
{
  base_offs_x = _current_text_dir == TD_RTL ? this->widget_w * (this->widgets_x - 1) : 0;
  base_offs_y = 0;
  start_x = 0;
  start_y = 0;
  if (this->sb != nullptr) {
    if (this->sb->IsVertical()) {
      start_y = this->sb->GetPosition() / this->widget_h;
      base_offs_y += -this->sb->GetPosition() + start_y * this->widget_h;
    } else {
      start_x = this->sb->GetPosition() / this->widget_w;
      int sub_x = this->sb->GetPosition() - start_x * this->widget_w;
      if (_current_text_dir == TD_RTL) {
        base_offs_x += sub_x;
      } else {
        base_offs_x -= sub_x;
      }
    }
  }
}

NWidgetBackground::NWidgetBackground(WidgetType tp, Colours colour, WidgetID index, std::unique_ptr<NWidgetPIPContainer> &&child) : NWidgetCore(tp, colour, index, 1, 1, {}, STR_NULL)
{
  assert(tp == WWT_PANEL || tp == WWT_INSET || tp == WWT_FRAME);
  this->child = std::move(child);
  if (this->child != nullptr) this->child->parent = this;
  this->SetAlignment(SA_TOP | SA_LEFT);
}

void NWidgetBackground::Add(std::unique_ptr<NWidgetBase> &&nwid)
{
  if (this->child == nullptr) {
    this->child = std::make_unique<NWidgetVertical>();
  }
  nwid->parent = this->child.get();
  this->child->Add(std::move(nwid));
}

void NWidgetBackground::SetPIP(uint8_t pip_pre, uint8_t pip_inter, uint8_t pip_post)
{
  if (this->child == nullptr) {
    this->child = std::make_unique<NWidgetVertical>();
  }
  this->child->parent = this;
  this->child->SetPIP(pip_pre, pip_inter, pip_post);
}

void NWidgetBackground::SetPIPRatio(uint8_t pip_ratio_pre, uint8_t pip_ratio_inter, uint8_t pip_ratio_post)
{
  if (this->child == nullptr) {
    this->child = std::make_unique<NWidgetVertical>();
  }
  this->child->parent = this;
  this->child->SetPIPRatio(pip_ratio_pre, pip_ratio_inter, pip_ratio_post);
}
 
void NWidgetBackground::AdjustPaddingForZoom()
{
  if (child != nullptr) child->AdjustPaddingForZoom();
  NWidgetCore::AdjustPaddingForZoom();
}
 
void NWidgetBackground::SetupSmallestSize(Window *w)
{
  if (this->child != nullptr) {
    this->child->SetupSmallestSize(w);
 
    this->smallest_x = this->child->smallest_x;
    this->smallest_y = this->child->smallest_y;
    this->fill_x = this->child->fill_x;
    this->fill_y = this->child->fill_y;
    this->resize_x = this->child->resize_x;
    this->resize_y = this->child->resize_y;
 
    /* Don't apply automatic padding if there is no child widget. */
    if (w == nullptr) return;
 
    if (this->type == WWT_FRAME) {
      std::string text = GetStringForWidget(w, this);
      Dimension text_size = text.empty() ? Dimension{0, 0} : GetStringBoundingBox(text, this->text_size);
 
      /* Account for the size of the frame's text if that exists */
      this->child->padding     = WidgetDimensions::scaled.frametext;
      this->child->padding.top = std::max<uint8_t>(WidgetDimensions::scaled.frametext.top, text_size.height != 0 ? text_size.height + WidgetDimensions::scaled.frametext.top / 2 : 0);
 
      this->smallest_x += this->child->padding.Horizontal();
      this->smallest_y += this->child->padding.Vertical();
 
      this->smallest_x = std::max(this->smallest_x, text_size.width + WidgetDimensions::scaled.frametext.Horizontal());
    } else if (this->type == WWT_INSET) {
      /* Apply automatic padding for bevel thickness. */
      this->child->padding = WidgetDimensions::scaled.bevel;
 
      this->smallest_x += this->child->padding.Horizontal();
      this->smallest_y += this->child->padding.Vertical();
    }
    this->ApplyAspectRatio();
  } else {
    Dimension d = {this->min_x, this->min_y};
    Dimension fill = {this->fill_x, this->fill_y};
    Dimension resize  = {this->resize_x, this->resize_y};
    if (w != nullptr) { // A non-nullptr window pointer acts as switch to turn dynamic widget size on.
      if (this->type == WWT_FRAME || this->type == WWT_INSET) {
        std::string text = GetStringForWidget(w, this);
        if (!text.empty()) {
          Dimension background = GetStringBoundingBox(text, this->text_size);
          background.width += (this->type == WWT_FRAME) ? (WidgetDimensions::scaled.frametext.Horizontal()) : (WidgetDimensions::scaled.inset.Horizontal());
          d = maxdim(d, background);
        }
      }
      if (this->index >= 0) {
        Dimension padding;
        switch (this->type) {
          default: NOT_REACHED();
          case WWT_PANEL: padding = {WidgetDimensions::scaled.framerect.Horizontal(), WidgetDimensions::scaled.framerect.Vertical()}; break;
          case WWT_FRAME: padding = {WidgetDimensions::scaled.frametext.Horizontal(), WidgetDimensions::scaled.frametext.Vertical()}; break;
          case WWT_INSET: padding = {WidgetDimensions::scaled.inset.Horizontal(),     WidgetDimensions::scaled.inset.Vertical()};     break;
        }
        w->UpdateWidgetSize(this->index, d, padding, fill, resize);
      }
    }
    this->smallest_x = d.width;
    this->smallest_y = d.height;
    this->fill_x = fill.width;
    this->fill_y = fill.height;
    this->resize_x = resize.width;
    this->resize_y = resize.height;
    this->ApplyAspectRatio();
  }
}
 
void NWidgetBackground::AssignSizePosition(SizingType sizing, int x, int y, uint given_width, uint given_height, bool rtl)
{
  this->StoreSizePosition(sizing, x, y, given_width, given_height);
 
  if (this->child != nullptr) {
    uint x_offset = (rtl ? this->child->padding.right : this->child->padding.left);
    uint width = given_width - this->child->padding.Horizontal();
    uint height = given_height - this->child->padding.Vertical();
    this->child->AssignSizePosition(sizing, x + x_offset, y + this->child->padding.top, width, height, rtl);
  }
}
 
void NWidgetBackground::FillWidgetLookup(WidgetLookup &widget_lookup)
{
  this->NWidgetCore::FillWidgetLookup(widget_lookup);
  if (this->child != nullptr) this->child->FillWidgetLookup(widget_lookup);
}
 
void NWidgetBackground::Draw(const Window *w)
{
  if (this->current_x == 0 || this->current_y == 0) return;
 
  Rect r = this->GetCurrentRect();
 
  const DrawPixelInfo *dpi = _cur_dpi;
  if (dpi->left > r.right || dpi->left + dpi->width <= r.left || dpi->top > r.bottom || dpi->top + dpi->height <= r.top) return;
 
  switch (this->type) {
    case WWT_PANEL:
      DrawFrameRect(r, this->colour, this->IsLowered() ? FrameFlag::Lowered : FrameFlags{});
      break;
 
    case WWT_FRAME:
      DrawFrame(r, this->colour, this->text_colour, GetStringForWidget(w, this), this->align, this->text_size);
      break;
 
    case WWT_INSET:
      DrawInset(r, this->colour, this->text_colour, GetStringForWidget(w, this), this->align, this->text_size);
      break;
 
    default:
      NOT_REACHED();
  }
 
  if (this->index >= 0) w->DrawWidget(r, this->index);
  if (this->child != nullptr) this->child->Draw(w);
 
  if (this->IsDisabled()) {
    GfxFillRect(r.Shrink(WidgetDimensions::scaled.bevel), GetColourGradient(this->colour, SHADE_DARKER), FILLRECT_CHECKER);
  }
 
  DrawOutline(w, this);
}
 
NWidgetCore *NWidgetBackground::GetWidgetFromPos(int x, int y)
{
  NWidgetCore *nwid = nullptr;
  if (IsInsideBS(x, this->pos_x, this->current_x) && IsInsideBS(y, this->pos_y, this->current_y)) {
    if (this->child != nullptr) nwid = this->child->GetWidgetFromPos(x, y);
    if (nwid == nullptr) nwid = this;
  }
  return nwid;
}
 
NWidgetBase *NWidgetBackground::GetWidgetOfType(WidgetType tp)
{
  NWidgetBase *nwid = nullptr;
  if (this->child != nullptr) nwid = this->child->GetWidgetOfType(tp);
  if (nwid == nullptr && this->type == tp) nwid = this;
  return nwid;
}
 
NWidgetViewport::NWidgetViewport(WidgetID index) : NWidgetCore(NWID_VIEWPORT, INVALID_COLOUR, index, 1, 1, {}, STR_NULL)
{
}
 
void NWidgetViewport::SetupSmallestSize(Window *)
{
  this->smallest_x = this->min_x;
  this->smallest_y = this->min_y;
  this->ApplyAspectRatio();
}
 
void NWidgetViewport::Draw(const Window *w)
{
  if (this->current_x == 0 || this->current_y == 0) return;
 
  if (this->disp_flags.Test(NWidgetDisplayFlag::NoTransparency)) {
    TransparencyOptionBits to_backup = _transparency_opt;
    _transparency_opt &= (1 << TO_SIGNS) | (1 << TO_TEXT); // Disable all transparency, except textual stuff
    w->DrawViewport();
    _transparency_opt = to_backup;
  } else {
    w->DrawViewport();
  }
 
  /* Optionally shade the viewport. */
  if (this->disp_flags.Any({NWidgetDisplayFlag::ShadeGrey, NWidgetDisplayFlag::ShadeDimmed})) {
    GfxFillRect(this->GetCurrentRect(), this->disp_flags.Test(NWidgetDisplayFlag::ShadeDimmed) ? PALETTE_TO_TRANSPARENT : PALETTE_NEWSPAPER, FILLRECT_RECOLOUR);
  }
 
  DrawOutline(w, this);
}

void NWidgetViewport::InitializeViewport(Window *w, std::variant<TileIndex, VehicleID> focus, ZoomLevel zoom)
{
  InitializeWindowViewport(w, this->pos_x, this->pos_y, this->current_x, this->current_y, focus, zoom);
}

void NWidgetViewport::UpdateViewportCoordinates(Window *w)
{
  if (w->viewport == nullptr) return;
 
  Viewport &vp = *w->viewport;
  vp.left = w->left + this->pos_x;
  vp.top  = w->top + this->pos_y;
  vp.width  = this->current_x;
  vp.height = this->current_y;
 
  vp.virtual_width  = ScaleByZoom(vp.width, vp.zoom);
  vp.virtual_height = ScaleByZoom(vp.height, vp.zoom);
}

Scrollbar::size_type Scrollbar::GetScrolledRowFromWidget(int clickpos, const Window * const w, WidgetID widget, int padding, int line_height) const
{
  int pos = w->GetRowFromWidget(clickpos, widget, padding, line_height);
  if (pos != INT_MAX) pos += this->GetPosition();
  return (pos < 0 || pos >= this->GetCount()) ? Scrollbar::npos : pos;
}

EventState Scrollbar::UpdateListPositionOnKeyPress(int &list_position, uint16_t keycode) const
{
  int new_pos = list_position;
  switch (keycode) {
    case WKC_UP:
      /* scroll up by one */
      new_pos--;
      break;
 
    case WKC_DOWN:
      /* scroll down by one */
      new_pos++;
      break;
 
    case WKC_PAGEUP:
      /* scroll up a page */
      new_pos -= this->GetCapacity();
      break;
 
    case WKC_PAGEDOWN:
      /* scroll down a page */
      new_pos += this->GetCapacity();
      break;
 
    case WKC_HOME:
      /* jump to beginning */
      new_pos = 0;
      break;
 
    case WKC_END:
      /* jump to end */
      new_pos = this->GetCount() - 1;
      break;
 
    default:
      return ES_NOT_HANDLED;
  }
 
  /* If there are no elements, there is nothing to scroll/update. */
  if (this->GetCount() != 0) {
    list_position = Clamp(new_pos, 0, this->GetCount() - 1);
  }
  return ES_HANDLED;
}
 

void Scrollbar::SetCapacityFromWidget(Window *w, WidgetID widget, int padding)
{
  NWidgetBase *nwid = w->GetWidget<NWidgetBase>(widget);
  if (this->IsVertical()) {
    this->SetCapacity(((int)nwid->current_y - padding) / (int)nwid->resize_y);
  } else {
    this->SetCapacity(((int)nwid->current_x - padding) / (int)nwid->resize_x);
  }
}

Rect ScrollRect(Rect r, const Scrollbar &sb, int resize_step)
{
  const int count = sb.GetCount() * resize_step;
  const int position = sb.GetPosition() * resize_step;
 
  if (sb.IsVertical()) {
    r.top -= position;
    r.bottom = r.top + count;
  } else {
    bool rtl = _current_text_dir == TD_RTL;
    if (rtl) {
      r.right += position;
      r.left = r.right - count;
    } else {
      r.left -= position;
      r.right = r.left + count;
    }
  }
 
  return r;
}

NWidgetScrollbar::NWidgetScrollbar(WidgetType tp, Colours colour, WidgetID index) : NWidgetCore(tp, colour, index, 1, 1, {}, STR_NULL), Scrollbar(tp != NWID_HSCROLLBAR)
{
  assert(tp == NWID_HSCROLLBAR || tp == NWID_VSCROLLBAR);
 
  switch (this->type) {
    case NWID_HSCROLLBAR:
      this->SetResize(1, 0);
      this->SetFill(1, 0);
      this->SetToolTip(STR_TOOLTIP_HSCROLL_BAR_SCROLLS_LIST);
      break;
 
    case NWID_VSCROLLBAR:
      this->SetResize(0, 1);
      this->SetFill(0, 1);
      this->SetToolTip(STR_TOOLTIP_VSCROLL_BAR_SCROLLS_LIST);
      break;
 
    default: NOT_REACHED();
  }
}
 
void NWidgetScrollbar::SetupSmallestSize(Window *)
{
  this->min_x = 0;
  this->min_y = 0;
 
  switch (this->type) {
    case NWID_HSCROLLBAR:
      this->SetMinimalSizeAbsolute(NWidgetScrollbar::GetHorizontalDimension().width * 3, NWidgetScrollbar::GetHorizontalDimension().height);
      break;
 
    case NWID_VSCROLLBAR:
      this->SetMinimalSizeAbsolute(NWidgetScrollbar::GetVerticalDimension().width, NWidgetScrollbar::GetVerticalDimension().height * 3);
      break;
 
    default: NOT_REACHED();
  }
 
  this->smallest_x = this->min_x;
  this->smallest_y = this->min_y;
}
 
void NWidgetScrollbar::Draw(const Window *w)
{
  if (this->current_x == 0 || this->current_y == 0) return;
 
  Rect r = this->GetCurrentRect();
 
  const DrawPixelInfo *dpi = _cur_dpi;
  if (dpi->left > r.right || dpi->left + dpi->width <= r.left || dpi->top > r.bottom || dpi->top + dpi->height <= r.top) return;
 
  bool up_lowered = this->disp_flags.Test(NWidgetDisplayFlag::ScrollbarUp);
  bool down_lowered = this->disp_flags.Test(NWidgetDisplayFlag::ScrollbarDown);
  bool middle_lowered = !this->disp_flags.Any({NWidgetDisplayFlag::ScrollbarUp, NWidgetDisplayFlag::ScrollbarDown}) && w->mouse_capture_widget == this->index;
 
  if (this->type == NWID_HSCROLLBAR) {
    DrawHorizontalScrollbar(r, this->colour, up_lowered, middle_lowered, down_lowered, this);
  } else {
    DrawVerticalScrollbar(r, this->colour, up_lowered, middle_lowered, down_lowered, this);
  }
 
  if (this->IsDisabled()) {
    GfxFillRect(r.Shrink(WidgetDimensions::scaled.bevel), GetColourGradient(this->colour, SHADE_DARKER), FILLRECT_CHECKER);
  }
 
  DrawOutline(w, this);
}
 
/* static */ void NWidgetScrollbar::InvalidateDimensionCache()
{
  vertical_dimension.width   = vertical_dimension.height   = 0;
  horizontal_dimension.width = horizontal_dimension.height = 0;
}
 
/* static */ Dimension NWidgetScrollbar::GetVerticalDimension()
{
  if (vertical_dimension.width == 0) {
    vertical_dimension = maxdim(GetScaledSpriteSize(SPR_ARROW_UP), GetScaledSpriteSize(SPR_ARROW_DOWN));
    vertical_dimension.width += WidgetDimensions::scaled.vscrollbar.Horizontal();
    vertical_dimension.height += WidgetDimensions::scaled.vscrollbar.Vertical();
  }
  return vertical_dimension;
}
 
/* static */ Dimension NWidgetScrollbar::GetHorizontalDimension()
{
  if (horizontal_dimension.width == 0) {
    horizontal_dimension = maxdim(GetScaledSpriteSize(SPR_ARROW_LEFT), GetScaledSpriteSize(SPR_ARROW_RIGHT));
    horizontal_dimension.width += WidgetDimensions::scaled.hscrollbar.Horizontal();
    horizontal_dimension.height += WidgetDimensions::scaled.hscrollbar.Vertical();
  }
  return horizontal_dimension;
}
 
Dimension NWidgetScrollbar::vertical_dimension = {0, 0};
Dimension NWidgetScrollbar::horizontal_dimension = {0, 0};

/* static */ void NWidgetLeaf::InvalidateDimensionCache()
{
  shadebox_dimension.width   = shadebox_dimension.height   = 0;
  debugbox_dimension.width   = debugbox_dimension.height   = 0;
  defsizebox_dimension.width = defsizebox_dimension.height = 0;
  stickybox_dimension.width  = stickybox_dimension.height  = 0;
  resizebox_dimension.width  = resizebox_dimension.height  = 0;
  closebox_dimension.width   = closebox_dimension.height   = 0;
  dropdown_dimension.width   = dropdown_dimension.height   = 0;
}
 
Dimension NWidgetLeaf::shadebox_dimension   = {0, 0};
Dimension NWidgetLeaf::debugbox_dimension   = {0, 0};
Dimension NWidgetLeaf::defsizebox_dimension = {0, 0};
Dimension NWidgetLeaf::stickybox_dimension  = {0, 0};
Dimension NWidgetLeaf::resizebox_dimension  = {0, 0};
Dimension NWidgetLeaf::closebox_dimension   = {0, 0};
Dimension NWidgetLeaf::dropdown_dimension   = {0, 0};

NWidgetLeaf::NWidgetLeaf(WidgetType tp, Colours colour, WidgetID index, const WidgetData &data, StringID tip) : NWidgetCore(tp, colour, index, 1, 1, data, tip)
{
  assert(index >= 0 || tp == WWT_LABEL || tp == WWT_TEXT || tp == WWT_CAPTION || tp == WWT_RESIZEBOX || tp == WWT_SHADEBOX || tp == WWT_DEFSIZEBOX || tp == WWT_DEBUGBOX || tp == WWT_STICKYBOX || tp == WWT_CLOSEBOX);
  this->min_x = 0;
  this->min_y = 0;
  this->SetResize(0, 0);
 
  switch (tp) {
    case WWT_EMPTY:
      if (colour != INVALID_COLOUR) [[unlikely]] throw std::runtime_error("WWT_EMPTY should not have a colour");
      break;
 
    case WWT_TEXT:
      if (colour != INVALID_COLOUR) [[unlikely]] throw std::runtime_error("WWT_TEXT should not have a colour");
      this->SetFill(0, 0);
      this->SetAlignment(SA_LEFT | SA_VERT_CENTER);
      break;
 
    case WWT_LABEL:
      if (colour != INVALID_COLOUR) [[unlikely]] throw std::runtime_error("WWT_LABEL should not have a colour");
      [[fallthrough]];
 
    case WWT_PUSHBTN:
    case WWT_IMGBTN:
    case WWT_PUSHIMGBTN:
    case WWT_IMGBTN_2:
    case WWT_TEXTBTN:
    case WWT_PUSHTXTBTN:
    case WWT_TEXTBTN_2:
    case WWT_IMGTEXTBTN:
    case WWT_PUSHIMGTEXTBTN:
    case WWT_BOOLBTN:
    case WWT_MATRIX:
    case NWID_BUTTON_DROPDOWN:
    case NWID_PUSHBUTTON_DROPDOWN:
      this->SetFill(0, 0);
      break;
 
    case WWT_ARROWBTN:
    case WWT_PUSHARROWBTN:
      this->SetFill(0, 0);
      this->SetAspect(WidgetDimensions::ASPECT_LEFT_RIGHT_BUTTON);
      break;
 
    case WWT_EDITBOX:
      this->SetFill(0, 0);
      break;
 
    case WWT_CAPTION:
      this->SetFill(1, 0);
      this->SetResize(1, 0);
      this->SetMinimalSize(0, WidgetDimensions::WD_CAPTION_HEIGHT);
      this->SetMinimalTextLines(1, WidgetDimensions::unscaled.captiontext.Vertical(), FS_NORMAL);
      this->SetToolTip(STR_TOOLTIP_WINDOW_TITLE_DRAG_THIS);
      break;
 
    case WWT_STICKYBOX:
      this->SetFill(0, 0);
      this->SetMinimalSize(WidgetDimensions::WD_STICKYBOX_WIDTH, WidgetDimensions::WD_CAPTION_HEIGHT);
      this->SetToolTip(STR_TOOLTIP_STICKY);
      this->SetAspect(this->min_x, this->min_y);
      break;
 
    case WWT_SHADEBOX:
      this->SetFill(0, 0);
      this->SetMinimalSize(WidgetDimensions::WD_SHADEBOX_WIDTH, WidgetDimensions::WD_CAPTION_HEIGHT);
      this->SetToolTip(STR_TOOLTIP_SHADE);
      this->SetAspect(this->min_x, this->min_y);
      break;
 
    case WWT_DEBUGBOX:
      this->SetFill(0, 0);
      this->SetMinimalSize(WidgetDimensions::WD_DEBUGBOX_WIDTH, WidgetDimensions::WD_CAPTION_HEIGHT);
      this->SetToolTip(STR_TOOLTIP_DEBUG);
      this->SetAspect(this->min_x, this->min_y);
      break;
 
    case WWT_DEFSIZEBOX:
      this->SetFill(0, 0);
      this->SetMinimalSize(WidgetDimensions::WD_DEFSIZEBOX_WIDTH, WidgetDimensions::WD_CAPTION_HEIGHT);
      this->SetToolTip(STR_TOOLTIP_DEFSIZE);
      this->SetAspect(this->min_x, this->min_y);
      break;
 
    case WWT_RESIZEBOX:
      this->SetFill(0, 0);
      this->SetMinimalSize(WidgetDimensions::WD_RESIZEBOX_WIDTH, 12);
      this->SetResizeWidgetType(RWV_SHOW_BEVEL);
      this->SetToolTip(STR_TOOLTIP_RESIZE);
      break;
 
    case WWT_CLOSEBOX:
      this->SetFill(0, 0);
      this->SetMinimalSize(WidgetDimensions::WD_CLOSEBOX_WIDTH, WidgetDimensions::WD_CAPTION_HEIGHT);
      this->SetToolTip(STR_TOOLTIP_CLOSE_WINDOW);
      this->SetAspect(this->min_x, this->min_y);
      break;
 
    case WWT_DROPDOWN:
      this->SetFill(0, 0);
      this->SetMinimalSize(0, WidgetDimensions::WD_DROPDOWN_HEIGHT);
      this->SetAlignment(SA_TOP | SA_LEFT);
      break;
 
    default:
      NOT_REACHED();
  }
}
 
void NWidgetLeaf::SetupSmallestSize(Window *w)
{
  Dimension padding = {0, 0};
  Dimension size = {this->min_x, this->min_y};
  Dimension fill = {this->fill_x, this->fill_y};
  Dimension resize = {this->resize_x, this->resize_y};
  switch (this->type) {
    case WWT_EMPTY: {
      break;
    }
    case WWT_MATRIX: {
      padding = {WidgetDimensions::scaled.matrix.Horizontal(), WidgetDimensions::scaled.matrix.Vertical()};
      break;
    }
    case WWT_SHADEBOX: {
      padding = {WidgetDimensions::scaled.shadebox.Horizontal(), WidgetDimensions::scaled.shadebox.Vertical()};
      if (NWidgetLeaf::shadebox_dimension.width == 0) {
        NWidgetLeaf::shadebox_dimension = maxdim(GetScaledSpriteSize(SPR_WINDOW_SHADE), GetScaledSpriteSize(SPR_WINDOW_UNSHADE));
        NWidgetLeaf::shadebox_dimension.width += padding.width;
        NWidgetLeaf::shadebox_dimension.height += padding.height;
      }
      size = maxdim(size, NWidgetLeaf::shadebox_dimension);
      break;
    }
    case WWT_DEBUGBOX:
      if (_settings_client.gui.newgrf_developer_tools && w->IsNewGRFInspectable()) {
        padding = {WidgetDimensions::scaled.debugbox.Horizontal(), WidgetDimensions::scaled.debugbox.Vertical()};
        if (NWidgetLeaf::debugbox_dimension.width == 0) {
          NWidgetLeaf::debugbox_dimension = GetScaledSpriteSize(SPR_WINDOW_DEBUG);
          NWidgetLeaf::debugbox_dimension.width += padding.width;
          NWidgetLeaf::debugbox_dimension.height += padding.height;
        }
        size = maxdim(size, NWidgetLeaf::debugbox_dimension);
      } else {
        /* If the setting is disabled we don't want to see it! */
        size.width = 0;
        fill.width = 0;
        resize.width = 0;
      }
      break;
 
    case WWT_STICKYBOX: {
      padding = {WidgetDimensions::scaled.stickybox.Horizontal(), WidgetDimensions::scaled.stickybox.Vertical()};
      if (NWidgetLeaf::stickybox_dimension.width == 0) {
        NWidgetLeaf::stickybox_dimension = maxdim(GetScaledSpriteSize(SPR_PIN_UP), GetScaledSpriteSize(SPR_PIN_DOWN));
        NWidgetLeaf::stickybox_dimension.width += padding.width;
        NWidgetLeaf::stickybox_dimension.height += padding.height;
      }
      size = maxdim(size, NWidgetLeaf::stickybox_dimension);
      break;
    }
 
    case WWT_DEFSIZEBOX: {
      padding = {WidgetDimensions::scaled.defsizebox.Horizontal(), WidgetDimensions::scaled.defsizebox.Vertical()};
      if (NWidgetLeaf::defsizebox_dimension.width == 0) {
        NWidgetLeaf::defsizebox_dimension = GetScaledSpriteSize(SPR_WINDOW_DEFSIZE);
        NWidgetLeaf::defsizebox_dimension.width += padding.width;
        NWidgetLeaf::defsizebox_dimension.height += padding.height;
      }
      size = maxdim(size, NWidgetLeaf::defsizebox_dimension);
      break;
    }
 
    case WWT_RESIZEBOX: {
      padding = {WidgetDimensions::scaled.resizebox.Horizontal(), WidgetDimensions::scaled.resizebox.Vertical()};
      if (NWidgetLeaf::resizebox_dimension.width == 0) {
        NWidgetLeaf::resizebox_dimension = maxdim(GetScaledSpriteSize(SPR_WINDOW_RESIZE_LEFT), GetScaledSpriteSize(SPR_WINDOW_RESIZE_RIGHT));
        NWidgetLeaf::resizebox_dimension.width += padding.width;
        NWidgetLeaf::resizebox_dimension.height += padding.height;
      }
      size = maxdim(size, NWidgetLeaf::resizebox_dimension);
      break;
    }
    case WWT_EDITBOX: {
      Dimension sprite_size = GetScaledSpriteSize(_current_text_dir == TD_RTL ? SPR_IMG_DELETE_RIGHT : SPR_IMG_DELETE_LEFT);
      size.width = std::max(size.width, ScaleGUITrad(30) + sprite_size.width);
      size.height = std::max(sprite_size.height, GetStringBoundingBox("_").height + WidgetDimensions::scaled.framerect.Vertical());
    }
    [[fallthrough]];
    case WWT_PUSHBTN: {
      padding = {WidgetDimensions::scaled.frametext.Horizontal(), WidgetDimensions::scaled.framerect.Vertical()};
      break;
    }
 
    case WWT_BOOLBTN:
      size.width = SETTING_BUTTON_WIDTH;
      size.height = SETTING_BUTTON_HEIGHT;
      break;
 
    case WWT_IMGBTN:
    case WWT_IMGBTN_2:
    case WWT_PUSHIMGBTN: {
      padding = {WidgetDimensions::scaled.imgbtn.Horizontal(), WidgetDimensions::scaled.imgbtn.Vertical()};
      Dimension d2 = GetScaledSpriteSize(this->widget_data.sprite);
      if (this->type == WWT_IMGBTN_2) d2 = maxdim(d2, GetScaledSpriteSize(this->widget_data.sprite + 1));
      d2.width += padding.width;
      d2.height += padding.height;
      size = maxdim(size, d2);
      break;
    }
 
    case WWT_IMGTEXTBTN:
    case WWT_PUSHIMGTEXTBTN: {
      padding = {WidgetDimensions::scaled.framerect.Horizontal(), WidgetDimensions::scaled.framerect.Vertical()};
      Dimension di = GetScaledSpriteSize(this->widget_data.sprite);
      Dimension dt = GetStringBoundingBox(GetStringForWidget(w, this), this->text_size);
      Dimension d2{
        padding.width + di.width + WidgetDimensions::scaled.hsep_wide + dt.width,
        padding.height + std::max(di.height, dt.height)
      };
      size = maxdim(size, d2);
      break;
    }
 
    case WWT_ARROWBTN:
    case WWT_PUSHARROWBTN: {
      padding = {WidgetDimensions::scaled.imgbtn.Horizontal(), WidgetDimensions::scaled.imgbtn.Vertical()};
      Dimension d2 = maxdim(GetScaledSpriteSize(SPR_ARROW_LEFT), GetScaledSpriteSize(SPR_ARROW_RIGHT));
      d2.width += padding.width;
      d2.height += padding.height;
      size = maxdim(size, d2);
      break;
    }
 
    case WWT_CLOSEBOX: {
      padding = {WidgetDimensions::scaled.closebox.Horizontal(), WidgetDimensions::scaled.closebox.Vertical()};
      if (NWidgetLeaf::closebox_dimension.width == 0) {
        NWidgetLeaf::closebox_dimension = GetScaledSpriteSize(SPR_CLOSEBOX);
        NWidgetLeaf::closebox_dimension.width += padding.width;
        NWidgetLeaf::closebox_dimension.height += padding.height;
      }
      size = maxdim(size, NWidgetLeaf::closebox_dimension);
      break;
    }
    case WWT_TEXTBTN:
    case WWT_PUSHTXTBTN:
    case WWT_TEXTBTN_2: {
      padding = {WidgetDimensions::scaled.framerect.Horizontal(), WidgetDimensions::scaled.framerect.Vertical()};
      Dimension d2 = GetStringBoundingBox(GetStringForWidget(w, this), this->text_size);
      d2.width += padding.width;
      d2.height += padding.height;
      size = maxdim(size, d2);
      break;
    }
    case WWT_LABEL:
    case WWT_TEXT: {
      size = maxdim(size, GetStringBoundingBox(GetStringForWidget(w, this), this->text_size));
      break;
    }
    case WWT_CAPTION: {
      padding = {WidgetDimensions::scaled.captiontext.Horizontal(), WidgetDimensions::scaled.captiontext.Vertical()};
      Dimension d2 = GetStringBoundingBox(GetStringForWidget(w, this), this->text_size);
      d2.width += padding.width;
      d2.height += padding.height;
      size = maxdim(size, d2);
      break;
    }
    case WWT_DROPDOWN:
    case NWID_BUTTON_DROPDOWN:
    case NWID_PUSHBUTTON_DROPDOWN: {
      if (NWidgetLeaf::dropdown_dimension.width == 0) {
        NWidgetLeaf::dropdown_dimension = GetScaledSpriteSize(SPR_ARROW_DOWN);
        NWidgetLeaf::dropdown_dimension.width += WidgetDimensions::scaled.vscrollbar.Horizontal();
        NWidgetLeaf::dropdown_dimension.height += WidgetDimensions::scaled.vscrollbar.Vertical();
      }
      padding = {WidgetDimensions::scaled.dropdowntext.Horizontal() + NWidgetLeaf::dropdown_dimension.width + WidgetDimensions::scaled.fullbevel.Horizontal(), WidgetDimensions::scaled.dropdowntext.Vertical()};
      Dimension d2 = GetStringBoundingBox(GetStringForWidget(w, this), this->text_size);
      d2.width += padding.width;
      d2.height = std::max(d2.height + padding.height, NWidgetLeaf::dropdown_dimension.height);
      size = maxdim(size, d2);
      break;
    }
    default:
      NOT_REACHED();
  }
 
  if (this->index >= 0) w->UpdateWidgetSize(this->index, size, padding, fill, resize);
 
  this->smallest_x = size.width;
  this->smallest_y = size.height;
  this->fill_x = fill.width;
  this->fill_y = fill.height;
  this->resize_x = resize.width;
  this->resize_y = resize.height;
  this->ApplyAspectRatio();
}
 
void NWidgetLeaf::Draw(const Window *w)
{
  if (this->current_x == 0 || this->current_y == 0) return;
 
  /* Setup a clipping rectangle... for WWT_EMPTY or WWT_TEXT, an extra scaled pixel is allowed in case text shadow encroaches. */
  int extra = (this->type == WWT_EMPTY || this->type == WWT_TEXT) ? ScaleGUITrad(1) : 0;
  DrawPixelInfo new_dpi;
  if (!FillDrawPixelInfo(&new_dpi, this->pos_x, this->pos_y, this->current_x + extra, this->current_y + extra)) return;
  /* ...but keep coordinates relative to the window. */
  new_dpi.left += this->pos_x;
  new_dpi.top += this->pos_y;
 
  AutoRestoreBackup dpi_backup(_cur_dpi, &new_dpi);
 
  Rect r = this->GetCurrentRect();
 
  bool clicked = this->IsLowered();
  switch (this->type) {
    case WWT_EMPTY:
      /* WWT_EMPTY used as a spacer indicates a potential design issue. */
      if (this->index == -1 && _draw_widget_outlines) {
        GfxFillRect(r, PC_BLACK, FILLRECT_CHECKER);
      }
      break;
 
    case WWT_PUSHBTN:
      DrawFrameRect(r, this->colour, clicked ? FrameFlag::Lowered : FrameFlags{});
      break;
 
    case WWT_BOOLBTN: {
      Point pt = GetAlignedPosition(r, Dimension(SETTING_BUTTON_WIDTH, SETTING_BUTTON_HEIGHT), this->align);
      Colours button_colour = this->widget_data.alternate_colour;
      if (button_colour == INVALID_COLOUR) button_colour = this->colour;
      DrawBoolButton(pt.x, pt.y, button_colour, this->colour, clicked, !this->IsDisabled());
      break;
    }
 
    case WWT_IMGBTN:
    case WWT_PUSHIMGBTN:
    case WWT_IMGBTN_2:
      DrawImageButtons(r, this->type, this->colour, clicked, this->widget_data.sprite, this->align);
      break;
 
    case WWT_TEXTBTN:
    case WWT_PUSHTXTBTN:
    case WWT_TEXTBTN_2:
      DrawFrameRect(r, this->colour, clicked ? FrameFlag::Lowered : FrameFlags{});
      DrawLabel(r, this->text_colour, GetStringForWidget(w, this, (type & WWT_MASK) == WWT_TEXTBTN_2 && clicked), this->align, this->text_size);
      break;
 
    case WWT_IMGTEXTBTN:
    case WWT_PUSHIMGTEXTBTN:
      DrawImageTextButtons(r, this->colour, clicked, this->widget_data.sprite, this->text_colour, GetStringForWidget(w, this), this->align, this->text_size);
      break;
 
    case WWT_ARROWBTN:
    case WWT_PUSHARROWBTN: {
      SpriteID sprite;
      switch (this->widget_data.arrow_widget_type) {
        case AWV_DECREASE: sprite = _current_text_dir != TD_RTL ? SPR_ARROW_LEFT : SPR_ARROW_RIGHT; break;
        case AWV_INCREASE: sprite = _current_text_dir == TD_RTL ? SPR_ARROW_LEFT : SPR_ARROW_RIGHT; break;
        case AWV_LEFT:     sprite = SPR_ARROW_LEFT;  break;
        case AWV_RIGHT:    sprite = SPR_ARROW_RIGHT; break;
        default: NOT_REACHED();
      }
      DrawImageButtons(r, WWT_PUSHIMGBTN, this->colour, clicked, sprite, this->align);
      break;
    }
 
    case WWT_LABEL:
      DrawLabel(r, this->text_colour, GetStringForWidget(w, this), this->align, this->text_size);
      break;
 
    case WWT_TEXT:
      DrawText(r, this->text_colour, GetStringForWidget(w, this), this->align, this->text_size);
      break;
 
    case WWT_MATRIX:
      DrawMatrix(r, this->colour, clicked, this->widget_data.matrix.width, this->widget_data.matrix.height, this->resize_x, this->resize_y);
      break;
 
    case WWT_EDITBOX: {
      const QueryString *query = w->GetQueryString(this->index);
      if (query != nullptr) query->DrawEditBox(w, this->index);
      break;
    }
 
    case WWT_CAPTION:
      DrawCaption(r, this->colour, w->owner, this->text_colour, GetStringForWidget(w, this), this->align, this->text_size);
      break;
 
    case WWT_SHADEBOX:
      DrawShadeBox(r, this->colour, w->IsShaded());
      break;
 
    case WWT_DEBUGBOX:
      DrawDebugBox(r, this->colour, clicked);
      break;
 
    case WWT_STICKYBOX:
      DrawStickyBox(r, this->colour, w->flags.Test(WindowFlag::Sticky));
      break;
 
    case WWT_DEFSIZEBOX:
      DrawDefSizeBox(r, this->colour, clicked);
      break;
 
    case WWT_RESIZEBOX:
      DrawResizeBox(r, this->colour, this->pos_x < (w->width / 2), w->flags.Test(WindowFlag::SizingLeft) || w->flags.Test(WindowFlag::SizingRight), this->widget_data.resize_widget_type == RWV_SHOW_BEVEL);
      break;
 
    case WWT_CLOSEBOX:
      DrawCloseBox(r, this->colour);
      break;
 
    case WWT_DROPDOWN:
      DrawButtonDropdown(r, this->colour, false, clicked, GetStringForWidget(w, this), this->align);
      break;
 
    case NWID_BUTTON_DROPDOWN:
    case NWID_PUSHBUTTON_DROPDOWN:
      DrawButtonDropdown(r, this->colour, clicked, this->disp_flags.Test(NWidgetDisplayFlag::DropdownActive), GetStringForWidget(w, this), this->align);
      break;
 
    default:
      NOT_REACHED();
  }
  if (this->index >= 0) w->DrawWidget(r, this->index);
 
  if (this->IsDisabled() && this->type != WWT_BOOLBTN) {
    /* WWT_BOOLBTN is excluded as it draws its own disabled state. */
    GfxFillRect(r.Shrink(WidgetDimensions::scaled.bevel), GetColourGradient(this->colour, SHADE_DARKER), FILLRECT_CHECKER);
  }
 
  DrawOutline(w, this);
}

bool NWidgetLeaf::ButtonHit(const Point &pt)
{
  if (_current_text_dir == TD_LTR) {
    int button_width = this->pos_x + this->current_x - NWidgetLeaf::dropdown_dimension.width;
    return pt.x < button_width;
  } else {
    int button_left = this->pos_x + NWidgetLeaf::dropdown_dimension.width;
    return pt.x >= button_left;
  }
}
 
/* == Conversion code from NWidgetPart array to NWidgetBase* tree == */

static bool IsAttributeWidgetPartType(WidgetType tp)
{
  return tp > WPT_ATTRIBUTE_BEGIN && tp < WPT_ATTRIBUTE_END;
}

void ApplyNWidgetPartAttribute(const NWidgetPart &nwid, NWidgetBase *dest)
{
  switch (nwid.type) {
    case WPT_RESIZE: {
      NWidgetResizeBase *nwrb = dynamic_cast<NWidgetResizeBase *>(dest);
      if (nwrb == nullptr) [[unlikely]] throw std::runtime_error("WPT_RESIZE requires NWidgetResizeBase");
      assert(nwid.u.xy.x >= 0 && nwid.u.xy.y >= 0);
      nwrb->SetResize(nwid.u.xy.x, nwid.u.xy.y);
      break;
    }
 
    case WPT_MINSIZE: {
      NWidgetResizeBase *nwrb = dynamic_cast<NWidgetResizeBase *>(dest);
      if (nwrb == nullptr) [[unlikely]] throw std::runtime_error("WPT_MINSIZE requires NWidgetResizeBase");
      assert(nwid.u.xy.x >= 0 && nwid.u.xy.y >= 0);
      nwrb->SetMinimalSize(nwid.u.xy.x, nwid.u.xy.y);
      break;
    }
 
    case WPT_MINTEXTLINES: {
      NWidgetResizeBase *nwrb = dynamic_cast<NWidgetResizeBase *>(dest);
      if (nwrb == nullptr) [[unlikely]] throw std::runtime_error("WPT_MINTEXTLINES requires NWidgetResizeBase");
      assert(nwid.u.text_lines.size >= FS_BEGIN && nwid.u.text_lines.size < FS_END);
      nwrb->SetMinimalTextLines(nwid.u.text_lines.lines, nwid.u.text_lines.spacing, nwid.u.text_lines.size);
      break;
    }
 
    case WPT_TEXTSTYLE: {
      NWidgetCore *nwc = dynamic_cast<NWidgetCore *>(dest);
      if (nwc == nullptr) [[unlikely]] throw std::runtime_error("WPT_TEXTSTYLE requires NWidgetCore");
      nwc->SetTextStyle(nwid.u.text_style.colour, nwid.u.text_style.size);
      break;
    }
 
    case WPT_ALIGNMENT: {
      NWidgetCore *nwc = dynamic_cast<NWidgetCore *>(dest);
      if (nwc == nullptr) [[unlikely]] throw std::runtime_error("WPT_ALIGNMENT requires NWidgetCore");
      nwc->SetAlignment(nwid.u.align.align);
      break;
    }
 
    case WPT_FILL: {
      NWidgetResizeBase *nwrb = dynamic_cast<NWidgetResizeBase *>(dest);
      if (nwrb == nullptr) [[unlikely]] throw std::runtime_error("WPT_FILL requires NWidgetResizeBase");
      nwrb->SetFill(nwid.u.xy.x, nwid.u.xy.y);
      break;
    }
 
    case WPT_DATATIP: {
      NWidgetCore *nwc = dynamic_cast<NWidgetCore *>(dest);
      if (nwc == nullptr) [[unlikely]] throw std::runtime_error("WPT_DATATIP requires NWidgetCore");
      nwc->widget_data = nwid.u.data_tip.data;
      nwc->SetToolTip(nwid.u.data_tip.tooltip);
      break;
    }
 
    case WPT_PADDING:
      if (dest == nullptr) [[unlikely]] throw std::runtime_error("WPT_PADDING requires NWidgetBase");
      dest->SetPadding(nwid.u.padding);
      break;
 
    case WPT_PIPSPACE: {
      NWidgetPIPContainer *nwc = dynamic_cast<NWidgetPIPContainer *>(dest);
      if (nwc != nullptr) nwc->SetPIP(nwid.u.pip.pre, nwid.u.pip.inter, nwid.u.pip.post);
 
      NWidgetBackground *nwb = dynamic_cast<NWidgetBackground *>(dest);
      if (nwb != nullptr) nwb->SetPIP(nwid.u.pip.pre, nwid.u.pip.inter, nwid.u.pip.post);
 
      if (nwc == nullptr && nwb == nullptr) [[unlikely]] throw std::runtime_error("WPT_PIPSPACE requires NWidgetPIPContainer or NWidgetBackground");
      break;
    }
 
    case WPT_PIPRATIO: {
      NWidgetPIPContainer *nwc = dynamic_cast<NWidgetPIPContainer *>(dest);
      if (nwc != nullptr) nwc->SetPIPRatio(nwid.u.pip.pre, nwid.u.pip.inter, nwid.u.pip.post);
 
      NWidgetBackground *nwb = dynamic_cast<NWidgetBackground *>(dest);
      if (nwb != nullptr) nwb->SetPIPRatio(nwid.u.pip.pre, nwid.u.pip.inter, nwid.u.pip.post);
 
      if (nwc == nullptr && nwb == nullptr) [[unlikely]] throw std::runtime_error("WPT_PIPRATIO requires NWidgetPIPContainer or NWidgetBackground");
      break;
    }
 
    case WPT_SCROLLBAR: {
      NWidgetCore *nwc = dynamic_cast<NWidgetCore *>(dest);
      if (nwc == nullptr) [[unlikely]] throw std::runtime_error("WPT_SCROLLBAR requires NWidgetCore");
      nwc->scrollbar_index = nwid.u.widget.index;
      break;
    }
 
    case WPT_ASPECT: {
      if (dest == nullptr) [[unlikely]] throw std::runtime_error("WPT_ASPECT requires NWidgetBase");
      dest->aspect_ratio = nwid.u.aspect.ratio;
      dest->aspect_flags = nwid.u.aspect.flags;
      break;
    }
 
    default:
      NOT_REACHED();
  }
}

static std::unique_ptr<NWidgetBase> MakeNWidget(const NWidgetPart &nwid)
{
  assert(!IsAttributeWidgetPartType(nwid.type));
  assert(nwid.type != WPT_ENDCONTAINER);
 
  switch (nwid.type) {
    case NWID_SPACER: return std::make_unique<NWidgetSpacer>(0, 0);
 
    case WWT_PANEL: [[fallthrough]];
    case WWT_INSET: [[fallthrough]];
    case WWT_FRAME: return std::make_unique<NWidgetBackground>(nwid.type, nwid.u.widget.colour, nwid.u.widget.index);
 
    case NWID_HORIZONTAL: return std::make_unique<NWidgetHorizontal>(nwid.u.container.flags, nwid.u.container.index);
    case NWID_HORIZONTAL_LTR: return std::make_unique<NWidgetHorizontalLTR>(nwid.u.container.flags, nwid.u.container.index);
    case NWID_VERTICAL: return std::make_unique<NWidgetVertical>(nwid.u.container.flags, nwid.u.container.index);
    case NWID_SELECTION: return std::make_unique<NWidgetStacked>(nwid.u.widget.index);
    case NWID_MATRIX: return std::make_unique<NWidgetMatrix>(nwid.u.widget.colour, nwid.u.widget.index);
    case NWID_VIEWPORT: return std::make_unique<NWidgetViewport>(nwid.u.widget.index);
    case NWID_LAYER: return std::make_unique<NWidgetLayer>(nwid.u.widget.index);
 
    case NWID_HSCROLLBAR: [[fallthrough]];
    case NWID_VSCROLLBAR: return std::make_unique<NWidgetScrollbar>(nwid.type, nwid.u.widget.colour, nwid.u.widget.index);
 
    case WPT_FUNCTION: return nwid.u.func_ptr();
 
    default:
      assert((nwid.type & WWT_MASK) < WWT_LAST || (nwid.type & WWT_MASK) == NWID_BUTTON_DROPDOWN);
      return std::make_unique<NWidgetLeaf>(nwid.type, nwid.u.widget.colour, nwid.u.widget.index, WidgetData{}, STR_NULL);
  }
}

static std::span<const NWidgetPart>::iterator MakeNWidget(std::span<const NWidgetPart>::iterator nwid_begin, std::span<const NWidgetPart>::iterator nwid_end, std::unique_ptr<NWidgetBase> &dest, bool &fill_dest)
{
  dest = nullptr;
 
  if (IsAttributeWidgetPartType(nwid_begin->type)) [[unlikely]] throw std::runtime_error("Expected non-attribute NWidgetPart type");
  if (nwid_begin->type == WPT_ENDCONTAINER) return nwid_begin;
 
  fill_dest = IsContainerWidgetType(nwid_begin->type);
  dest = MakeNWidget(*nwid_begin);
  if (dest == nullptr) return nwid_begin;
 
  ++nwid_begin;
 
  /* Once a widget is created, we're now looking for attributes. */
  while (nwid_begin != nwid_end && IsAttributeWidgetPartType(nwid_begin->type)) {
    ApplyNWidgetPartAttribute(*nwid_begin, dest.get());
    ++nwid_begin;
  }
 
  return nwid_begin;
}

bool IsContainerWidgetType(WidgetType tp)
{
  return tp == NWID_HORIZONTAL || tp == NWID_HORIZONTAL_LTR || tp == NWID_VERTICAL || tp == NWID_MATRIX
    || tp == WWT_PANEL || tp == WWT_FRAME || tp == WWT_INSET || tp == NWID_SELECTION || tp == NWID_LAYER;
}

static std::span<const NWidgetPart>::iterator MakeWidgetTree(std::span<const NWidgetPart>::iterator nwid_begin, std::span<const NWidgetPart>::iterator nwid_end, std::unique_ptr<NWidgetBase> &parent)
{
  /* If *parent == nullptr, only the first widget is read and returned. Otherwise, *parent must point to either
   * a #NWidgetContainer or a #NWidgetBackground object, and parts are added as much as possible. */
  NWidgetContainer *nwid_cont = dynamic_cast<NWidgetContainer *>(parent.get());
  NWidgetBackground *nwid_parent = dynamic_cast<NWidgetBackground *>(parent.get());
  assert(parent == nullptr || (nwid_cont != nullptr && nwid_parent == nullptr) || (nwid_cont == nullptr && nwid_parent != nullptr));
 
  while (nwid_begin != nwid_end) {
    std::unique_ptr<NWidgetBase> sub_widget = nullptr;
    bool fill_sub = false;
    nwid_begin = MakeNWidget(nwid_begin, nwid_end, sub_widget, fill_sub);
 
    /* Break out of loop when end reached */
    if (sub_widget == nullptr) break;
 
    /* If sub-widget is a container, recursively fill that container. */
    if (fill_sub && IsContainerWidgetType(sub_widget->type)) {
      nwid_begin = MakeWidgetTree(nwid_begin, nwid_end, sub_widget);
    }
 
    /* Add sub_widget to parent container if available, otherwise return the widget to the caller. */
    if (nwid_cont != nullptr) nwid_cont->Add(std::move(sub_widget));
    if (nwid_parent != nullptr) nwid_parent->Add(std::move(sub_widget));
    if (nwid_cont == nullptr && nwid_parent == nullptr) {
      parent = std::move(sub_widget);
      return nwid_begin;
    }
  }
 
  if (nwid_begin == nwid_end) return nwid_begin; // Reached the end of the array of parts?
 
  assert(nwid_begin < nwid_end);
  assert(nwid_begin->type == WPT_ENDCONTAINER);
  return std::next(nwid_begin); // *nwid_begin is also 'used'
}

std::unique_ptr<NWidgetBase> MakeNWidgets(std::span<const NWidgetPart> nwid_parts, std::unique_ptr<NWidgetBase> &&container)
{
  if (container == nullptr) container = std::make_unique<NWidgetVertical>();
  [[maybe_unused]] auto nwid_part = MakeWidgetTree(std::begin(nwid_parts), std::end(nwid_parts), container);
#ifdef WITH_ASSERT
  if (nwid_part != std::end(nwid_parts)) [[unlikely]] throw std::runtime_error("Did not consume all NWidgetParts");
#endif
  return std::move(container);
}

std::unique_ptr<NWidgetBase> MakeWindowNWidgetTree(std::span<const NWidgetPart> nwid_parts, NWidgetStacked **shade_select)
{
  auto nwid_begin = std::begin(nwid_parts);
  auto nwid_end = std::end(nwid_parts);
 
  *shade_select = nullptr;
 
  /* Read the first widget recursively from the array. */
  std::unique_ptr<NWidgetBase> nwid = nullptr;
  nwid_begin = MakeWidgetTree(nwid_begin, nwid_end, nwid);
  assert(nwid != nullptr);
 
  NWidgetHorizontal *hor_cont = dynamic_cast<NWidgetHorizontal *>(nwid.get());
 
  auto root = std::make_unique<NWidgetVertical>();
  root->Add(std::move(nwid));
  if (nwid_begin == nwid_end) return root; // There is no body at all.
 
  if (hor_cont != nullptr && hor_cont->GetWidgetOfType(WWT_CAPTION) != nullptr && hor_cont->GetWidgetOfType(WWT_SHADEBOX) != nullptr) {
    /* If the first widget has a title bar and a shade box, silently add a shade selection widget in the tree. */
    auto shade_stack = std::make_unique<NWidgetStacked>(INVALID_WIDGET);
    *shade_select = shade_stack.get();
    /* Load the remaining parts into the shade stack. */
    shade_stack->Add(MakeNWidgets({nwid_begin, nwid_end}, std::make_unique<NWidgetVertical>()));
    root->Add(std::move(shade_stack));
    return root;
  }
 
  /* Load the remaining parts into 'root'. */
  return MakeNWidgets({nwid_begin, nwid_end}, std::move(root));
}

std::unique_ptr<NWidgetBase> MakeCompanyButtonRows(WidgetID widget_first, WidgetID widget_last, Colours button_colour, int max_length, StringID button_tooltip, bool resizable)
{
  assert(max_length >= 1);
  std::unique_ptr<NWidgetVertical> vert = nullptr; // Storage for all rows.
  std::unique_ptr<NWidgetHorizontal> hor = nullptr; // Storage for buttons in one row.
  int hor_length = 0;
 
  Dimension sprite_size = GetSpriteSize(SPR_COMPANY_ICON, nullptr, ZoomLevel::Normal);
  sprite_size.width  += WidgetDimensions::unscaled.matrix.Horizontal();
  sprite_size.height += WidgetDimensions::unscaled.matrix.Vertical();
 
  for (WidgetID widnum = widget_first; widnum <= widget_last; widnum++) {
    /* Ensure there is room in 'hor' for another button. */
    if (hor_length == max_length) {
      if (vert == nullptr) vert = std::make_unique<NWidgetVertical>();
      vert->Add(std::move(hor));
      hor = nullptr;
      hor_length = 0;
    }
    if (hor == nullptr) {
      hor = std::make_unique<NWidgetHorizontal>();
      hor_length = 0;
    }
 
    auto panel = std::make_unique<NWidgetBackground>(WWT_PANEL, button_colour, widnum);
    panel->SetMinimalSize(sprite_size.width, sprite_size.height);
    panel->SetFill(1, 1);
    if (resizable) panel->SetResize(1, 0);
    panel->SetToolTip(button_tooltip);
    hor->Add(std::move(panel));
    hor_length++;
  }
  if (vert == nullptr) return hor; // All buttons fit in a single row.
 
  if (hor_length > 0 && hor_length < max_length) {
    /* Last row is partial, add a spacer at the end to force all buttons to the left. */
    auto spc = std::make_unique<NWidgetSpacer>(sprite_size.width, sprite_size.height);
    spc->SetFill(1, 1);
    if (resizable) spc->SetResize(1, 0);
    hor->Add(std::move(spc));
  }
  if (hor != nullptr) vert->Add(std::move(hor));
  return vert;
}

void NWidgetContainer::UnfocusWidgets(Window *parent_window)
{
  assert(parent_window != nullptr);
  if (parent_window->nested_focus != nullptr) {
    for (auto &widget : this->children) {
      if (parent_window->nested_focus == widget.get()) {
        parent_window->UnfocusFocusedWidget();
      }
    }
  }
}