LibWeb: Fix clip of hidden overflow when translated boxes are involved

There is a problem with current approach where overflow clip rectange is
calculated by aggregating intersection of absolute padding boxes of
boxes in containing block chain that resulting rectangle doesn't
respect transform properties.

To solve this problem `PaintableBox` is changed to store clip rectangle
saved from painter because it does respect transform properties of all
previously applied clip rectangles.

Author: kalenikaliaksandr

Userland/Libraries/LibGfx/Painter.h

@@ -177,6 +177,7 @@ class Painter {
     }
 
     IntRect clip_rect() const { return state().clip_rect; }
+    void set_clip_rect(IntRect const& rect) { state().clip_rect = rect; }
 
     int scale() const { return state().scale; }
 

Userland/Libraries/LibWeb/Painting/PaintableBox.cpp

@@ -313,24 +313,8 @@ BorderRadiiData PaintableBox::normalized_border_radii_data(ShrinkRadiiForBorders
     return border_radius_data;
 }
 
-Optional<CSSPixelRect> PaintableBox::clip_rect() const
+Optional<Gfx::IntRect> PaintableBox::clip_rect() const
 {
-    if (!m_clip_rect.has_value()) {
-        if (containing_block() && containing_block()->paint_box())
-            m_clip_rect = containing_block()->paint_box()->clip_rect();
-
-        auto overflow_x = computed_values().overflow_x();
-        auto overflow_y = computed_values().overflow_y();
-
-        if (overflow_x == CSS::Overflow::Hidden && overflow_y == CSS::Overflow::Hidden) {
-            if (m_clip_rect.has_value()) {
-                m_clip_rect->intersect(absolute_padding_box_rect());
-            } else {
-                m_clip_rect = absolute_padding_box_rect();
-            }
-        }
-    }
-
     return m_clip_rect;
 }
 
@@ -339,27 +323,36 @@ void PaintableBox::before_children_paint(PaintContext& context, PaintPhase phase
     if (!AK::first_is_one_of(phase, PaintPhase::Background, PaintPhase::Border, PaintPhase::Foreground))
         return;
 
-    // FIXME: Support more overflow variations.
-    auto clip_rect = this->clip_rect();
+    auto clip_rect = context.painter().clip_rect();
+    if (containing_block() && containing_block()->paint_box()) {
+        if (containing_block()->paint_box()->clip_rect().has_value()) {
+            clip_rect = *containing_block()->paint_box()->clip_rect();
+        }
+    }
+    context.painter().set_clip_rect(clip_rect);
+
     auto overflow_x = computed_values().overflow_x();
     auto overflow_y = computed_values().overflow_y();
 
     auto clip_overflow = [&] {
         if (!m_clipping_overflow) {
             context.painter().save();
-            context.painter().add_clip_rect(context.rounded_device_rect(*clip_rect).to_type<int>());
+            context.painter().add_clip_rect(context.rounded_device_rect(absolute_padding_box_rect()).to_type<int>());
             m_clipping_overflow = true;
         }
     };
 
-    if (clip_rect.has_value()) {
+    // FIXME: Support more overflow variations.
+    if (overflow_x == CSS::Overflow::Hidden && overflow_y == CSS::Overflow::Hidden) {
         clip_overflow();
     }
 
+    m_clip_rect = context.painter().clip_rect();
+
     if (overflow_y == CSS::Overflow::Hidden || overflow_x == CSS::Overflow::Hidden) {
         auto border_radii_data = normalized_border_radii_data(ShrinkRadiiForBorders::Yes);
         if (border_radii_data.has_any_radius()) {
-            auto corner_clipper = BorderRadiusCornerClipper::create(context, context.rounded_device_rect(*clip_rect), border_radii_data, CornerClip::Outside, BorderRadiusCornerClipper::UseCachedBitmap::No);
+            auto corner_clipper = BorderRadiusCornerClipper::create(context, context.rounded_device_rect(absolute_padding_box_rect()), border_radii_data, CornerClip::Outside, BorderRadiusCornerClipper::UseCachedBitmap::No);
             if (corner_clipper.is_error()) {
                 dbgln("Failed to create overflow border-radius corner clipper: {}", corner_clipper.error());
                 return;

Userland/Libraries/LibWeb/Painting/PaintableBox.h

@@ -98,7 +98,7 @@ class PaintableBox : public Paintable {
         return m_overflow_data->scrollable_overflow_rect;
     }
 
-    Optional<CSSPixelRect> clip_rect() const;
+    Optional<Gfx::IntRect> clip_rect() const;
 
     void set_overflow_data(Optional<OverflowData> data) { m_overflow_data = move(data); }
     void set_containing_line_box_fragment(Optional<Layout::LineBoxFragmentCoordinate>);
@@ -157,7 +157,7 @@ class PaintableBox : public Paintable {
     Optional<CSSPixelRect> mutable m_absolute_rect;
     Optional<CSSPixelRect> mutable m_absolute_paint_rect;
 
-    Optional<CSSPixelRect> mutable m_clip_rect;
+    Gfx::IntRect mutable m_clip_rect;
 
     mutable bool m_clipping_overflow { false };
     Optional<BorderRadiusCornerClipper> mutable m_overflow_corner_radius_clipper;