From ee4ba7617ce8e99df953cff0b345974eb1f7098e Mon Sep 17 00:00:00 2001
From: Aliaksandr Kalenik <kalenik.aliaksandr@gmail.com>
Date: Wed, 25 Jan 2023 02:57:50 +0300
Subject: [PATCH] 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.
---
 Userland/Libraries/LibGfx/Painter.h           |  1 +
 .../LibWeb/Painting/PaintableBox.cpp          | 37 ++++++++-----------
 .../Libraries/LibWeb/Painting/PaintableBox.h  |  4 +-
 3 files changed, 18 insertions(+), 24 deletions(-)

diff --git a/Userland/Libraries/LibGfx/Painter.h b/Userland/Libraries/LibGfx/Painter.h
index 5f4804ca01..e1f9c542fa 100644
--- a/Userland/Libraries/LibGfx/Painter.h
+++ b/Userland/Libraries/LibGfx/Painter.h
@@ -177,6 +177,7 @@ public:
     }
 
     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; }
 
diff --git a/Userland/Libraries/LibWeb/Painting/PaintableBox.cpp b/Userland/Libraries/LibWeb/Painting/PaintableBox.cpp
index 9e9c9bf866..f63cbd709f 100644
--- a/Userland/Libraries/LibWeb/Painting/PaintableBox.cpp
+++ b/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;
diff --git a/Userland/Libraries/LibWeb/Painting/PaintableBox.h b/Userland/Libraries/LibWeb/Painting/PaintableBox.h
index 170041772e..eb3b8125d5 100644
--- a/Userland/Libraries/LibWeb/Painting/PaintableBox.h
+++ b/Userland/Libraries/LibWeb/Painting/PaintableBox.h
@@ -98,7 +98,7 @@ public:
         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 @@ private:
     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;