LibWeb: Support CSS property background-clip: text

From https://drafts.csswg.org/css-backgrounds-4/#background-clip
"The background is painted within (clipped to) the intersection of the
border box and the geometry of the text in the element and its in-flow
and floated descendants"

This change implements it in the following way:
1. Traverse the descendants of the element, collecting the Gfx::Path of
   glyphs into a vector.
2. The vector of collected paths is saved in the background painting
   command.
3. The painting commands executor uses the list of glyphs to paint a
   mask for background clipping.

Co-authored-by: Aliaksandr Kalenik <kalenik.aliaksandr@gmail.com>

Userland/Libraries/LibWeb/CSS/StyleValues/AbstractImageStyleValue.h

@@ -36,7 +36,7 @@ public:
     virtual void resolve_for_size(Layout::NodeWithStyleAndBoxModelMetrics const&, CSSPixelSize) const {};
 
     virtual bool is_paintable() const = 0;
-    virtual void paint(PaintContext& context, DevicePixelRect const& dest_rect, ImageRendering) const = 0;
+    virtual void paint(PaintContext& context, DevicePixelRect const& dest_rect, ImageRendering, Vector<Gfx::Path> const& clip_paths = {}) const = 0;
 
     virtual Optional<Gfx::Color> color_if_single_pixel_bitmap() const { return {}; }
 };

Userland/Libraries/LibWeb/CSS/StyleValues/ConicGradientStyleValue.cpp

@@ -42,10 +42,10 @@ void ConicGradientStyleValue::resolve_for_size(Layout::NodeWithStyleAndBoxModelM
     m_resolved->position = m_properties.position->resolved(node, CSSPixelRect { { 0, 0 }, size });
 }
 
-void ConicGradientStyleValue::paint(PaintContext& context, DevicePixelRect const& dest_rect, CSS::ImageRendering) const
+void ConicGradientStyleValue::paint(PaintContext& context, DevicePixelRect const& dest_rect, CSS::ImageRendering, Vector<Gfx::Path> const& clip_paths) const
 {
     VERIFY(m_resolved.has_value());
-    Painting::paint_conic_gradient(context, dest_rect, m_resolved->data, context.rounded_device_point(m_resolved->position));
+    Painting::paint_conic_gradient(context, dest_rect, m_resolved->data, context.rounded_device_point(m_resolved->position), clip_paths);
 }
 
 bool ConicGradientStyleValue::equals(StyleValue const& other) const

Userland/Libraries/LibWeb/CSS/StyleValues/ConicGradientStyleValue.h

@@ -25,7 +25,7 @@ public:
 
     virtual String to_string() const override;
 
-    void paint(PaintContext&, DevicePixelRect const& dest_rect, CSS::ImageRendering) const override;
+    void paint(PaintContext&, DevicePixelRect const& dest_rect, CSS::ImageRendering, Vector<Gfx::Path> const& clip_paths = {}) const override;
 
     virtual bool equals(StyleValue const& other) const override;
 

Userland/Libraries/LibWeb/CSS/StyleValues/ImageStyleValue.cpp

@@ -131,11 +131,11 @@ Optional<CSSPixelFraction> ImageStyleValue::natural_aspect_ratio() const
     return {};
 }
 
-void ImageStyleValue::paint(PaintContext& context, DevicePixelRect const& dest_rect, CSS::ImageRendering image_rendering) const
+void ImageStyleValue::paint(PaintContext& context, DevicePixelRect const& dest_rect, CSS::ImageRendering image_rendering, Vector<Gfx::Path> const& clip_paths) const
 {
     if (auto const* b = bitmap(m_current_frame_index, dest_rect.size().to_type<int>()); b != nullptr) {
         auto scaling_mode = to_gfx_scaling_mode(image_rendering, b->rect(), dest_rect.to_type<int>());
-        context.recording_painter().draw_scaled_immutable_bitmap(dest_rect.to_type<int>(), *b, b->rect(), scaling_mode);
+        context.recording_painter().draw_scaled_immutable_bitmap(dest_rect.to_type<int>(), *b, b->rect(), scaling_mode, clip_paths);
     }
 }
 

Userland/Libraries/LibWeb/CSS/StyleValues/ImageStyleValue.h

@@ -45,7 +45,7 @@ public:
     Optional<CSSPixelFraction> natural_aspect_ratio() const override;
 
     virtual bool is_paintable() const override;
-    void paint(PaintContext& context, DevicePixelRect const& dest_rect, CSS::ImageRendering image_rendering) const override;
+    void paint(PaintContext& context, DevicePixelRect const& dest_rect, CSS::ImageRendering image_rendering, Vector<Gfx::Path> const& clip_paths = {}) const override;
 
     virtual Optional<Gfx::Color> color_if_single_pixel_bitmap() const override;
 

Userland/Libraries/LibWeb/CSS/StyleValues/LinearGradientStyleValue.cpp

@@ -109,10 +109,10 @@ void LinearGradientStyleValue::resolve_for_size(Layout::NodeWithStyleAndBoxModel
     m_resolved = ResolvedData { Painting::resolve_linear_gradient_data(node, size, *this), size };
 }
 
-void LinearGradientStyleValue::paint(PaintContext& context, DevicePixelRect const& dest_rect, CSS::ImageRendering) const
+void LinearGradientStyleValue::paint(PaintContext& context, DevicePixelRect const& dest_rect, CSS::ImageRendering, Vector<Gfx::Path> const& clip_paths) const
 {
     VERIFY(m_resolved.has_value());
-    Painting::paint_linear_gradient(context, dest_rect, m_resolved->data);
+    Painting::paint_linear_gradient(context, dest_rect, m_resolved->data, clip_paths);
 }
 
 }

Userland/Libraries/LibWeb/CSS/StyleValues/LinearGradientStyleValue.h

@@ -60,7 +60,7 @@ public:
     void resolve_for_size(Layout::NodeWithStyleAndBoxModelMetrics const&, CSSPixelSize) const override;
 
     bool is_paintable() const override { return true; }
-    void paint(PaintContext& context, DevicePixelRect const& dest_rect, CSS::ImageRendering image_rendering) const override;
+    void paint(PaintContext& context, DevicePixelRect const& dest_rect, CSS::ImageRendering image_rendering, Vector<Gfx::Path> const& clip_paths = {}) const override;
 
 private:
     LinearGradientStyleValue(GradientDirection direction, Vector<LinearColorStopListElement> color_stop_list, GradientType type, GradientRepeating repeating)

Userland/Libraries/LibWeb/CSS/StyleValues/RadialGradientStyleValue.cpp

@@ -207,12 +207,13 @@ bool RadialGradientStyleValue::equals(StyleValue const& other) const
     return m_properties == other_gradient.m_properties;
 }
 
-void RadialGradientStyleValue::paint(PaintContext& context, DevicePixelRect const& dest_rect, CSS::ImageRendering) const
+void RadialGradientStyleValue::paint(PaintContext& context, DevicePixelRect const& dest_rect, CSS::ImageRendering, Vector<Gfx::Path> const& clip_paths) const
 {
     VERIFY(m_resolved.has_value());
     Painting::paint_radial_gradient(context, dest_rect, m_resolved->data,
         context.rounded_device_point(m_resolved->center),
-        context.rounded_device_size(m_resolved->gradient_size));
+        context.rounded_device_size(m_resolved->gradient_size),
+        clip_paths);
 }
 
 }

Userland/Libraries/LibWeb/CSS/StyleValues/RadialGradientStyleValue.h

@@ -51,7 +51,7 @@ public:
 
     virtual String to_string() const override;
 
-    void paint(PaintContext&, DevicePixelRect const& dest_rect, CSS::ImageRendering) const override;
+    void paint(PaintContext&, DevicePixelRect const& dest_rect, CSS::ImageRendering, Vector<Gfx::Path> const& clip_paths = {}) const override;
 
     virtual bool equals(StyleValue const& other) const override;