Change: Ability to set aspect ratio of a widget.

This allows setting the shape of a widget without dealing with absolute pixel sizes.

src/widget.cpp

@@ -925,6 +925,20 @@ 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 & AspectFlags::ResizeX) == AspectFlags::ResizeX) x = std::max(this->smallest_x, static_cast<uint>(this->smallest_y * std::abs(this->aspect_ratio)));
+	if ((this->aspect_flags & AspectFlags::ResizeY) == AspectFlags::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);
@@ -942,6 +956,28 @@ NWidgetResizeBase::NWidgetResizeBase(WidgetType tp, uint fill_x, uint fill_y) :
 	this->fill_y = fill_y;
 }
 
+/**
+ * Set desired aspect ratio of this widget.
+ * @param ratio Desired aspect ratio, or 0 for none.
+ * @param flags Dimensions which should be resized.
+ */
+void NWidgetResizeBase::SetAspect(float ratio, AspectFlags flags)
+{
+	this->aspect_ratio = ratio;
+	this->aspect_flags = flags;
+}
+
+/**
+ * Set desired aspect ratio of this widget, in terms of horizontal and vertical dimensions.
+ * @param x_ratio Desired horizontal component of aspect ratio.
+ * @param y_ratio Desired vertical component of aspect ratio.
+ * @param flags Dimensions which should be resized.
+ */
+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) {
@@ -1224,6 +1260,7 @@ void NWidgetStacked::SetupSmallestSize(Window *w)
 		this->fill_y = fill.height;
 		this->resize_x = resize.width;
 		this->resize_y = resize.height;
+		this->ApplyAspectRatio();
 		return;
 	}
 
@@ -1243,6 +1280,7 @@ void NWidgetStacked::SetupSmallestSize(Window *w)
 		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();
 	}
 }
 
@@ -1405,6 +1443,11 @@ void NWidgetHorizontal::SetupSmallestSize(Window *w)
 		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 & NC_EQUALSIZE) {
 		for (const auto &child_wid : this->children) {
 			if (child_wid->fill_x == 1) child_wid->smallest_x = longest;
@@ -1594,6 +1637,11 @@ void NWidgetVertical::SetupSmallestSize(Window *w)
 		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 & NC_EQUALSIZE) {
 		for (const auto &child_wid : this->children) {
 			if (child_wid->fill_y == 1) child_wid->smallest_y = highest;
@@ -1730,6 +1778,7 @@ void NWidgetSpacer::SetupSmallestSize(Window *)
 {
 	this->smallest_x = this->min_x;
 	this->smallest_y = this->min_y;
+	this->ApplyAspectRatio();
 }
 
 void NWidgetSpacer::FillWidgetLookup(WidgetLookup &)
@@ -1841,6 +1890,7 @@ void NWidgetMatrix::SetupSmallestSize(Window *w)
 	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)
@@ -2089,6 +2139,7 @@ void NWidgetBackground::SetupSmallestSize(Window *w)
 			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};
@@ -2117,6 +2168,7 @@ void NWidgetBackground::SetupSmallestSize(Window *w)
 		this->fill_y = fill.height;
 		this->resize_x = resize.width;
 		this->resize_y = resize.height;
+		this->ApplyAspectRatio();
 	}
 }
 
@@ -2203,6 +2255,7 @@ void NWidgetViewport::SetupSmallestSize(Window *)
 {
 	this->smallest_x = this->min_x;
 	this->smallest_y = this->min_y;
+	this->ApplyAspectRatio();
 }
 
 void NWidgetViewport::Draw(const Window *w)
@@ -2738,6 +2791,7 @@ void NWidgetLeaf::SetupSmallestSize(Window *w)
 	this->fill_y = fill.height;
 	this->resize_x = resize.width;
 	this->resize_y = resize.height;
+	this->ApplyAspectRatio();
 }
 
 void NWidgetLeaf::Draw(const Window *w)
@@ -3045,6 +3099,13 @@ static const NWidgetPart *MakeNWidget(const NWidgetPart *nwid_begin, const NWidg
 				break;
 			}
 
+			case WPT_ASPECT: {
+				if (dest == nullptr) [[unlikely]] throw std::runtime_error("WPT_ASPECT requires NWidgetBase");
+				dest->aspect_ratio = nwid_begin->u.aspect.ratio;
+				dest->aspect_flags = nwid_begin->u.aspect.flags;
+				break;
+			}
+
 			case WPT_ENDCONTAINER:
 				return nwid_begin;