LibWeb: Extract border-radius normalization code from Box

This is going to be needed by InlineNodes too!

`BorderPainting.{h,cpp}` might not be the best place for it, but it
works for now.

Userland/Libraries/LibWeb/Layout/Box.cpp

@@ -299,28 +299,13 @@ void Box::paint_box_shadow(PaintContext& context)
         context.painter().blit(rect.location() + blur_rect_position, *new_bitmap, rect);
 }
 
-Box::BorderRadiusData Box::normalized_border_radius_data()
+Painting::BorderRadiusData Box::normalized_border_radius_data()
 {
-    // FIXME: some values should be relative to the height() if specified, but which? For now, all relative values are relative to the width.
+    return Painting::normalized_border_radius_data(*this, bordered_rect(),
-    auto bottom_left_radius = computed_values().border_bottom_left_radius().resolved_or_zero(*this, width()).to_px(*this);
+        computed_values().border_top_left_radius(),
-    auto bottom_right_radius = computed_values().border_bottom_right_radius().resolved_or_zero(*this, width()).to_px(*this);
+        computed_values().border_top_right_radius(),
-    auto top_left_radius = computed_values().border_top_left_radius().resolved_or_zero(*this, width()).to_px(*this);
+        computed_values().border_bottom_right_radius(),
-    auto top_right_radius = computed_values().border_top_right_radius().resolved_or_zero(*this, width()).to_px(*this);
+        computed_values().border_bottom_left_radius());
-
-    // Scale overlapping curves according to https://www.w3.org/TR/css-backgrounds-3/#corner-overlap
-    auto bordered_rect = this->bordered_rect();
-    auto f = 1.0f;
-    f = min(f, bordered_rect.width() / (float)(top_left_radius + top_right_radius));
-    f = min(f, bordered_rect.height() / (float)(top_right_radius + bottom_right_radius));
-    f = min(f, bordered_rect.width() / (float)(bottom_left_radius + bottom_right_radius));
-    f = min(f, bordered_rect.height() / (float)(top_left_radius + bottom_left_radius));
-
-    top_left_radius = (int)(top_left_radius * f);
-    top_right_radius = (int)(top_right_radius * f);
-    bottom_right_radius = (int)(bottom_right_radius * f);
-    bottom_left_radius = (int)(bottom_left_radius * f);
-
-    return { top_left_radius, top_right_radius, bottom_right_radius, bottom_left_radius };
 }
 
 // https://www.w3.org/TR/css-display-3/#out-of-flow

Userland/Libraries/LibWeb/Layout/Box.h

@@ -10,6 +10,7 @@
 #include <LibGfx/Rect.h>
 #include <LibWeb/Layout/LineBox.h>
 #include <LibWeb/Layout/Node.h>
+#include <LibWeb/Painting/BorderPainting.h>
 #include <LibWeb/Painting/StackingContext.h>
 
 namespace Web::Layout {
@@ -125,14 +126,7 @@ public:
 
     virtual float width_of_logical_containing_block() const;
 
-    struct BorderRadiusData {
+    Painting::BorderRadiusData normalized_border_radius_data();
-        float top_left { 0 };
-        float top_right { 0 };
-        float bottom_right { 0 };
-        float bottom_left { 0 };
-    };
-
-    BorderRadiusData normalized_border_radius_data();
 
 protected:
     Box(DOM::Document& document, DOM::Node* node, NonnullRefPtr<CSS::StyleProperties> style)

Userland/Libraries/LibWeb/Painting/BorderPainting.cpp

@@ -10,6 +10,29 @@
 
 namespace Web::Painting {
 
+BorderRadiusData normalized_border_radius_data(Layout::Node const& node, Gfx::FloatRect const& rect, CSS::Length top_left_radius, CSS::Length top_right_radius, CSS::Length bottom_right_radius, CSS::Length bottom_left_radius)
+{
+    // FIXME: some values should be relative to the height() if specified, but which? For now, all relative values are relative to the width.
+    auto bottom_left_radius_px = bottom_left_radius.resolved_or_zero(node, rect.width()).to_px(node);
+    auto bottom_right_radius_px = bottom_right_radius.resolved_or_zero(node, rect.width()).to_px(node);
+    auto top_left_radius_px = top_left_radius.resolved_or_zero(node, rect.width()).to_px(node);
+    auto top_right_radius_px = top_right_radius.resolved_or_zero(node, rect.width()).to_px(node);
+
+    // Scale overlapping curves according to https://www.w3.org/TR/css-backgrounds-3/#corner-overlap
+    auto f = 1.0f;
+    f = min(f, rect.width() / (float)(top_left_radius_px + top_right_radius_px));
+    f = min(f, rect.height() / (float)(top_right_radius_px + bottom_right_radius_px));
+    f = min(f, rect.width() / (float)(bottom_left_radius_px + bottom_right_radius_px));
+    f = min(f, rect.height() / (float)(top_left_radius_px + bottom_left_radius_px));
+
+    top_left_radius_px = (int)(top_left_radius_px * f);
+    top_right_radius_px = (int)(top_right_radius_px * f);
+    bottom_right_radius_px = (int)(bottom_right_radius_px * f);
+    bottom_left_radius_px = (int)(bottom_left_radius_px * f);
+
+    return BorderRadiusData { top_left_radius_px, top_right_radius_px, bottom_right_radius_px, bottom_left_radius_px };
+}
+
 void paint_border(PaintContext& context, BorderEdge edge, const Gfx::FloatRect& rect, const CSS::ComputedValues& style)
 {
     const auto& border_data = [&] {

Userland/Libraries/LibWeb/Painting/BorderPainting.h

@@ -11,6 +11,14 @@
 
 namespace Web::Painting {
 
+struct BorderRadiusData {
+    float top_left { 0 };
+    float top_right { 0 };
+    float bottom_right { 0 };
+    float bottom_left { 0 };
+};
+BorderRadiusData normalized_border_radius_data(Layout::Node const&, Gfx::FloatRect const&, CSS::Length top_left_radius, CSS::Length top_right_radius, CSS::Length bottom_right_radius, CSS::Length bottom_left_radius);
+
 enum class BorderEdge {
     Top,
     Right,