From 4d86cee91c4307c8bb4fe2a8b6874b661482b179 Mon Sep 17 00:00:00 2001
From: Xianzhu Wang <wangxianzhu@chromium.org>
Date: Wed, 13 Nov 2024 22:17:29 +0000
Subject: [PATCH] Fix solid color thumb quad under large scale

If a layer has a large scale, visible_layer_rect() can't reliably
clip a quad before scaling because a "pixel" in the layer is very
large and scale-after-clip will create a quad exceeding the clip.

clip
  large-scale
    layer

Now share more code with the non-solid-color-thumb code path.

For a AppendQuads method, to ensure the clip rect is applied, it's
better to call PopulateScaledSharedQuadState() instead of creating a
shared quad state by itself.

Bug: 377948403
Change-Id: I8d7dd08fe9fc7907685bfbaa1a5fd5682688aed0
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6014683
Reviewed-by: Philip Rogers <pdr@chromium.org>
Commit-Queue: Xianzhu Wang <wangxianzhu@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1382613}
---

diff --git a/cc/layers/painted_scrollbar_layer_impl.cc b/cc/layers/painted_scrollbar_layer_impl.cc
index ed9b32b..12fb191 100644
--- a/cc/layers/painted_scrollbar_layer_impl.cc
+++ b/cc/layers/painted_scrollbar_layer_impl.cc
@@ -109,19 +109,28 @@
     AppendQuadsData* append_quads_data) const {
   viz::SharedQuadState* shared_quad_state =
       render_pass->CreateAndAppendSharedQuadState();
-  if (thumb_color_.has_value()) {
-    const gfx::Rect thumb_rect = ComputeThumbQuadRect();
-    if (thumb_rect.IsEmpty()) {
-      return;
-    }
-    gfx::Rect visible_thumb_rect =
-        draw_properties().occlusion_in_content_space.GetUnoccludedContentRect(
-            thumb_rect);
-    visible_thumb_rect.Intersect(visible_layer_rect());
-    if (visible_thumb_rect.IsEmpty()) {
-      return;
-    }
+  // The thumb sqs must be non-opaque so that the track and buttons will not be
+  // occluded in viz by the thumb's 'quad_layer_rect'.
+  constexpr bool kContentsOpaque = false;
+  PopulateScaledSharedQuadState(shared_quad_state, internal_contents_scale_,
+                                kContentsOpaque);
 
+  AppendDebugBorderQuad(render_pass, gfx::Rect(internal_content_bounds_),
+                        shared_quad_state, append_quads_data);
+
+  const gfx::Rect thumb_quad_rect = ComputeThumbQuadRect();
+  const gfx::Rect scaled_thumb_quad_rect =
+      gfx::ScaleToEnclosingRect(thumb_quad_rect, internal_contents_scale_);
+  const gfx::Rect visible_thumb_quad_rect =
+      draw_properties().occlusion_in_content_space.GetUnoccludedContentRect(
+          thumb_quad_rect);
+  if (visible_thumb_quad_rect.IsEmpty()) {
+    return;
+  }
+  const gfx::Rect scaled_visible_thumb_quad_rect = gfx::ScaleToEnclosingRect(
+      visible_thumb_quad_rect, internal_contents_scale_);
+
+  if (thumb_color_.has_value()) {
     gfx::MaskFilterInfo rounded_corners_mask =
         draw_properties().mask_filter_info;
     // Web tests draw the thumb as a square to avoid issues that come with the
@@ -130,24 +139,18 @@
     if (!is_web_test() && IsFluentScrollbarEnabled()) {
       const int rounded_corner_radius =
           orientation() == ScrollbarOrientation::kHorizontal
-              ? thumb_rect.height()
-              : thumb_rect.width();
-      rounded_corners_mask = gfx::MaskFilterInfo(
-          gfx::RRectF(gfx::RectF(thumb_rect), rounded_corner_radius));
-      rounded_corners_mask.ApplyTransform(
+              ? thumb_quad_rect.height()
+              : thumb_quad_rect.width();
+      shared_quad_state->mask_filter_info = gfx::MaskFilterInfo(
+          gfx::RRectF(gfx::RectF(thumb_quad_rect), rounded_corner_radius));
+      shared_quad_state->mask_filter_info.ApplyTransform(
           draw_properties().target_space_transform);
     }
-    shared_quad_state->SetAll(
-        draw_properties().target_space_transform, thumb_rect,
-        visible_thumb_rect, rounded_corners_mask, /*clip=*/std::nullopt,
-        /*contents_opaque=*/false, draw_properties().opacity,
-        /*blend=*/SkBlendMode::kSrcOver, GetSortingContextId(),
-        static_cast<uint32_t>(id()),
-        /*fast_rounded_corner=*/true);
     auto* thumb_quad =
         render_pass->CreateAndAppendDrawQuad<viz::SolidColorDrawQuad>();
-    thumb_quad->SetNew(shared_quad_state, thumb_rect, visible_thumb_rect,
-                       thumb_color_.value(), /*anti_aliasing_off=*/false);
+    thumb_quad->SetNew(shared_quad_state, scaled_thumb_quad_rect,
+                       scaled_visible_thumb_quad_rect, thumb_color_.value(),
+                       /*anti_aliasing_off=*/false);
     ValidateQuadResources(thumb_quad);
     return;
   }
@@ -159,26 +162,9 @@
     return;
   }
 
-  // The thumb sqs must be non-opaque so that the track and buttons will not be
-  // occluded in viz by the thumb's 'quad_layer_rect'.
-  constexpr bool kContentsOpaque = false;
-  PopulateScaledSharedQuadState(shared_quad_state, internal_contents_scale_,
-                                kContentsOpaque);
-
-  AppendDebugBorderQuad(render_pass, gfx::Rect(internal_content_bounds_),
-                        shared_quad_state, append_quads_data);
-  gfx::Rect thumb_quad_rect = ComputeThumbQuadRect();
-  gfx::Rect scaled_thumb_quad_rect =
-      gfx::ScaleToEnclosingRect(thumb_quad_rect, internal_contents_scale_);
-  gfx::Rect visible_thumb_quad_rect =
-      draw_properties().occlusion_in_content_space.GetUnoccludedContentRect(
-          thumb_quad_rect);
-  gfx::Rect scaled_visible_thumb_quad_rect = gfx::ScaleToEnclosingRect(
-      visible_thumb_quad_rect, internal_contents_scale_);
   viz::ResourceId thumb_resource_id =
       layer_tree_impl()->ResourceIdForUIResource(thumb_ui_resource_id_);
-
-  if (!thumb_resource_id || visible_thumb_quad_rect.IsEmpty()) {
+  if (!thumb_resource_id) {
     return;
   }
 
diff --git a/cc/layers/painted_scrollbar_layer_impl_unittest.cc b/cc/layers/painted_scrollbar_layer_impl_unittest.cc
index 26ff7c4..6ea79f9d 100644
--- a/cc/layers/painted_scrollbar_layer_impl_unittest.cc
+++ b/cc/layers/painted_scrollbar_layer_impl_unittest.cc
@@ -65,8 +65,7 @@
   impl.CalcDrawProps(viewport_size);
 
   gfx::Rect thumb_rect = scrollbar_layer_impl->ComputeThumbQuadRect();
-  EXPECT_EQ(gfx::Rect(0, 500 / 4, 10, layer_size.height() / 2).ToString(),
-            thumb_rect.ToString());
+  EXPECT_EQ(gfx::Rect(0, 500 / 4, 10, layer_size.height() / 2), thumb_rect);
 
   {
     SCOPED_TRACE("No occlusion");
@@ -97,16 +96,14 @@
         viz::TextureDrawQuad::MaterialCast(track_and_buttons_draw_quad);
 
     gfx::Rect scaled_thumb_rect = gfx::ScaleToEnclosingRect(thumb_rect, scale);
-    EXPECT_EQ(track_and_buttons_quad->rect.ToString(),
-              gfx::Rect(scaled_layer_size).ToString());
+    EXPECT_EQ(track_and_buttons_quad->rect, gfx::Rect(scaled_layer_size));
     EXPECT_EQ(scrollbar_layer_impl->contents_opaque(),
               track_and_buttons_quad->shared_quad_state->are_contents_opaque);
-    EXPECT_EQ(track_and_buttons_quad->visible_rect.ToString(),
-              gfx::Rect(scaled_layer_size).ToString());
+    EXPECT_EQ(track_and_buttons_quad->visible_rect,
+              gfx::Rect(scaled_layer_size));
     EXPECT_FALSE(track_and_buttons_quad->needs_blending);
-    EXPECT_EQ(thumb_quad->rect.ToString(), scaled_thumb_rect.ToString());
-    EXPECT_EQ(thumb_quad->visible_rect.ToString(),
-              scaled_thumb_rect.ToString());
+    EXPECT_EQ(thumb_quad->rect, scaled_thumb_rect);
+    EXPECT_EQ(thumb_quad->visible_rect, scaled_thumb_rect);
     EXPECT_TRUE(thumb_quad->needs_blending);
     EXPECT_FALSE(thumb_quad->shared_quad_state->are_contents_opaque);
 
@@ -184,8 +181,8 @@
   impl.CalcDrawProps(viewport_size);
 
   gfx::Rect thumb_rect = scrollbar_layer_impl->ComputeThumbQuadRect();
-  EXPECT_EQ(gfx::Rect(2, 500 / 4, 11, layer_size.height() / 2).ToString(),
-            thumb_rect.ToString());
+  EXPECT_EQ(gfx::Rect(2, 500 / 4, 11, layer_size.height() / 2), thumb_rect);
+  gfx::Rect scaled_thumb_rect = gfx::ScaleToEnclosingRect(thumb_rect, scale);
 
   {
     SCOPED_TRACE("No occlusion");
@@ -220,8 +217,8 @@
     EXPECT_EQ(track_and_buttons_quad->visible_rect,
               gfx::Rect(scaled_layer_size));
     EXPECT_FALSE(track_and_buttons_quad->needs_blending);
-    EXPECT_EQ(thumb_quad->rect, thumb_rect);
-    EXPECT_EQ(thumb_quad->visible_rect, thumb_rect);
+    EXPECT_EQ(thumb_quad->rect, scaled_thumb_rect);
+    EXPECT_EQ(thumb_quad->visible_rect, scaled_thumb_rect);
     EXPECT_FALSE(thumb_quad->needs_blending);
     EXPECT_FALSE(thumb_quad->shared_quad_state->are_contents_opaque);
 
@@ -252,6 +249,84 @@
   }
 }
 
+TEST(PaintedScrollbarLayerImplTest,
+     SolidColorThumbNinePatchTrackUnderClipAndScale) {
+  gfx::Size layer_size(15, 1000);
+  gfx::Rect clip_rect(0, 0, 1000, 1000);
+  float scale = 33.f;

diff --git a/cc/layers/painted_scrollbar_layer_impl_unittest.cc b/cc/layers/painted_scrollbar_layer_impl_unittest.cc
index 26ff7c4..6ea79f9d 100644
--- a/cc/layers/painted_scrollbar_layer_impl_unittest.cc
+++ b/cc/layers/painted_scrollbar_layer_impl_unittest.cc
@@ -65,8 +65,7 @@
   impl.CalcDrawProps(viewport_size);
 
   gfx::Rect thumb_rect = scrollbar_layer_impl->ComputeThumbQuadRect();
-  EXPECT_EQ(gfx::Rect(0, 500 / 4, 10, layer_size.height() / 2).ToString(),
-            thumb_rect.ToString());
+  EXPECT_EQ(gfx::Rect(0, 500 / 4, 10, layer_size.height() / 2), thumb_rect);
 
   {
     SCOPED_TRACE("No occlusion");
@@ -97,16 +96,14 @@
         viz::TextureDrawQuad::MaterialCast(track_and_buttons_draw_quad);
 
     gfx::Rect scaled_thumb_rect = gfx::ScaleToEnclosingRect(thumb_rect, scale);
-    EXPECT_EQ(track_and_buttons_quad->rect.ToString(),
-              gfx::Rect(scaled_layer_size).ToString());
+    EXPECT_EQ(track_and_buttons_quad->rect, gfx::Rect(scaled_layer_size));
     EXPECT_EQ(scrollbar_layer_impl->contents_opaque(),
               track_and_buttons_quad->shared_quad_state->are_contents_opaque);
-    EXPECT_EQ(track_and_buttons_quad->visible_rect.ToString(),
-              gfx::Rect(scaled_layer_size).ToString());
+    EXPECT_EQ(track_and_buttons_quad->visible_rect,
+              gfx::Rect(scaled_layer_size));
     EXPECT_FALSE(track_and_buttons_quad->needs_blending);
-    EXPECT_EQ(thumb_quad->rect.ToString(), scaled_thumb_rect.ToString());
-    EXPECT_EQ(thumb_quad->visible_rect.ToString(),
-              scaled_thumb_rect.ToString());
+    EXPECT_EQ(thumb_quad->rect, scaled_thumb_rect);
+    EXPECT_EQ(thumb_quad->visible_rect, scaled_thumb_rect);
     EXPECT_TRUE(thumb_quad->needs_blending);
     EXPECT_FALSE(thumb_quad->shared_quad_state->are_contents_opaque);
 
@@ -184,8 +181,8 @@
   impl.CalcDrawProps(viewport_size);
 
   gfx::Rect thumb_rect = scrollbar_layer_impl->ComputeThumbQuadRect();
-  EXPECT_EQ(gfx::Rect(2, 500 / 4, 11, layer_size.height() / 2).ToString(),
-            thumb_rect.ToString());
+  EXPECT_EQ(gfx::Rect(2, 500 / 4, 11, layer_size.height() / 2), thumb_rect);
+  gfx::Rect scaled_thumb_rect = gfx::ScaleToEnclosingRect(thumb_rect, scale);
 
   {
     SCOPED_TRACE("No occlusion");
@@ -220,8 +217,8 @@
     EXPECT_EQ(track_and_buttons_quad->visible_rect,
               gfx::Rect(scaled_layer_size));
     EXPECT_FALSE(track_and_buttons_quad->needs_blending);
-    EXPECT_EQ(thumb_quad->rect, thumb_rect);
-    EXPECT_EQ(thumb_quad->visible_rect, thumb_rect);
+    EXPECT_EQ(thumb_quad->rect, scaled_thumb_rect);
+    EXPECT_EQ(thumb_quad->visible_rect, scaled_thumb_rect);
     EXPECT_FALSE(thumb_quad->needs_blending);
     EXPECT_FALSE(thumb_quad->shared_quad_state->are_contents_opaque);
 
@@ -252,6 +249,84 @@
   }
 }
 
+TEST(PaintedScrollbarLayerImplTest,
+     SolidColorThumbNinePatchTrackUnderClipAndScale) {
+  gfx::Size layer_size(15, 1000);
+  gfx::Rect clip_rect(0, 0, 1000, 1000);
+  float scale = 33.f;
+  gfx::Size scaled_layer_size = gfx::ScaleToCeiledSize(layer_size, scale);
+  gfx::Size viewport_size(1000, 1000);
+
+  LayerTreeImplTestBase impl;
+
+  SkBitmap thumb_sk_bitmap;
+  thumb_sk_bitmap.allocN32Pixels(10, 10);
+  thumb_sk_bitmap.setImmutable();
+  UIResourceId thumb_uid = 5;
+  UIResourceBitmap thumb_bitmap(thumb_sk_bitmap);
+  impl.host_impl()->CreateUIResource(thumb_uid, thumb_bitmap);
+
+  SkBitmap track_and_buttons_sk_bitmap;
+  track_and_buttons_sk_bitmap.allocN32Pixels(10, 10);
+  track_and_buttons_sk_bitmap.setImmutable();
+  UIResourceId track_and_buttons_uid = 6;
+  UIResourceBitmap track_and_buttons_bitmap(track_and_buttons_sk_bitmap);
+  impl.host_impl()->CreateUIResource(track_and_buttons_uid,
+                                     track_and_buttons_bitmap);
+
+  ScrollbarOrientation orientation = ScrollbarOrientation::kVertical;
+
+  PaintedScrollbarLayerImpl* scrollbar_layer_impl =
+      impl.AddLayerInActiveTree<PaintedScrollbarLayerImpl>(orientation, false,
+                                                           false);
+  scrollbar_layer_impl->SetBounds(layer_size);
+  scrollbar_layer_impl->SetContentsOpaque(true);
+  scrollbar_layer_impl->set_internal_contents_scale_and_bounds(
+      scale, scaled_layer_size);
+  scrollbar_layer_impl->SetDrawsContent(true);
+  scrollbar_layer_impl->SetThumbThickness(11);
+  scrollbar_layer_impl->SetThumbLength(500);
+  scrollbar_layer_impl->SetTrackRect(gfx::Rect(0, 0, 15, layer_size.height()));
+  scrollbar_layer_impl->SetCurrentPos(100.f / 4);
+  scrollbar_layer_impl->SetClipLayerLength(100.f);
+  scrollbar_layer_impl->SetScrollLayerLength(200.f);
+  scrollbar_layer_impl->set_track_and_buttons_ui_resource_id(
+      track_and_buttons_uid);
+  scrollbar_layer_impl->SetThumbColor(SkColors::kRed);
+
+  CopyProperties(impl.root_layer(), scrollbar_layer_impl);
+  CreateClipNode(scrollbar_layer_impl).clip = gfx::RectF(clip_rect);
+  CreateTransformNode(scrollbar_layer_impl).local.Scale(scale);
+
+  impl.CalcDrawProps(viewport_size);
+
+  gfx::Rect thumb_rect = scrollbar_layer_impl->ComputeThumbQuadRect();
+  EXPECT_EQ(gfx::Rect(2, 500 / 4, 11, layer_size.height() / 2), thumb_rect);
+  gfx::Rect scaled_thumb_rect = gfx::ScaleToEnclosingRect(thumb_rect, scale);
+
+  impl.AppendQuads(scrollbar_layer_impl);
+  EXPECT_EQ(2u, impl.quad_list().size());
+
+  const viz::SolidColorDrawQuad* thumb_quad =
+      viz::SolidColorDrawQuad::MaterialCast(impl.quad_list().ElementAt(0));
+  EXPECT_EQ(thumb_quad->rect, scaled_thumb_rect);
+  EXPECT_EQ(thumb_quad->visible_rect, scaled_thumb_rect);
+  EXPECT_FALSE(thumb_quad->needs_blending);
+  EXPECT_FALSE(thumb_quad->shared_quad_state->are_contents_opaque);
+  EXPECT_EQ(1.f, thumb_quad->shared_quad_state->opacity);
+
+  const viz::TextureDrawQuad* track_and_buttons_quad =
+      viz::TextureDrawQuad::MaterialCast(impl.quad_list().ElementAt(1));
+  EXPECT_EQ(track_and_buttons_quad->shared_quad_state->clip_rect, clip_rect);
+  EXPECT_EQ(track_and_buttons_quad->rect, gfx::Rect(scaled_layer_size));
+  EXPECT_EQ(scrollbar_layer_impl->contents_opaque(),
+            track_and_buttons_quad->shared_quad_state->are_contents_opaque);
+  EXPECT_EQ(track_and_buttons_quad->visible_rect, gfx::Rect(scaled_layer_size));
+  EXPECT_FALSE(track_and_buttons_quad->needs_blending);
+  EXPECT_EQ(track_and_buttons_quad->shared_quad_state->clip_rect, clip_rect);
+  EXPECT_EQ(1.f, track_and_buttons_quad->shared_quad_state->opacity);
+}
+
 TEST(PaintedScrollbarLayerImplTest, PaintedOpacityChangesInvalidate) {
   LayerTreeImplTestBase impl;
   ScrollbarOrientation orientation = ScrollbarOrientation::kVertical;
@@ -339,7 +414,7 @@
     : public PaintedScrollbarLayerImplSolidColorThumbTest {
  protected:
   void SetUp() override {
-    LayerTreeSettings settings;
+    LayerTreeSettings settings = CommitToPendingTreeLayerListSettings();
     settings.enable_fluent_overlay_scrollbar = true;
     settings.enable_fluent_scrollbar = true;
     impl_ = std::make_unique<LayerTreeImplTestBase>(settings);
@@ -394,6 +469,9 @@
   scrollbar_layer_impl->SetThumbThickness(
       scrollbar_layer_impl->GetIdleThicknessScale());
 
+  CopyProperties(impl_->root_layer(), scrollbar_layer_impl);
+  impl_->CalcDrawProps(gfx::Size(500, 500));
+
   // AppendThumbQuads should return early after checking that there is no
   // `thumb_color_` and Fluent scrollbars are enabled.
   // AppendTrackQuads should return early when the Fluent overlay code decides
diff --git a/third_party/blink/web_tests/external/wpt/css/css-overflow/scrollbar-large-scale-in-iframe-ref.html b/third_party/blink/web_tests/external/wpt/css/css-overflow/scrollbar-large-scale-in-iframe-ref.html
new file mode 100644
index 0000000..38c8d0c
--- /dev/null
+++ b/third_party/blink/web_tests/external/wpt/css/css-overflow/scrollbar-large-scale-in-iframe-ref.html
@@ -0,0 +1,3 @@
+<!DOCTYPE html>
+<div style="position: absolute; top: 100px; left: 100px;
+            width: 100px; height: 100px; background: green"></div>
diff --git a/third_party/blink/web_tests/external/wpt/css/css-overflow/scrollbar-large-scale-in-iframe.html b/third_party/blink/web_tests/external/wpt/css/css-overflow/scrollbar-large-scale-in-iframe.html
new file mode 100644
index 0000000..1808d1d
--- /dev/null
+++ b/third_party/blink/web_tests/external/wpt/css/css-overflow/scrollbar-large-scale-in-iframe.html
@@ -0,0 +1,12 @@
+<!DOCTYPE html>
+<link rel="help" href="https://crbug.com/377948403">
+<link rel="match" href="scrollbar-large-scale-in-iframe-ref.html">
+<iframe style="position: absolute; top: 100px; left: 100px;
+               border: none; width: 100px; height: 100px"
+        srcdoc="
+  <select multiple style='transform: scale(500, 10)'>
+    <optgroup style='height: 1000px'></optgroup>
+  </select>">
+</iframe>
+<div style="position: absolute; top: 100px; left: 100px;
+            width: 100px; height: 100px; background: green"></div>
diff --git a/third_party/blink/web_tests/platform/linux/fast/sub-pixel/transformed-iframe-copy-on-scroll-expected.png b/third_party/blink/web_tests/platform/linux/fast/sub-pixel/transformed-iframe-copy-on-scroll-expected.png
index 21e6518a..47ab936 100644
--- a/third_party/blink/web_tests/platform/linux/fast/sub-pixel/transformed-iframe-copy-on-scroll-expected.png
+++ b/third_party/blink/web_tests/platform/linux/fast/sub-pixel/transformed-iframe-copy-on-scroll-expected.png
Binary files differ
diff --git a/third_party/blink/web_tests/platform/win/fast/frames/iframe-scaling-with-scroll-expected.png b/third_party/blink/web_tests/platform/win/fast/frames/iframe-scaling-with-scroll-expected.png
index b3caa2d..fdfac45 100644
--- a/third_party/blink/web_tests/platform/win/fast/frames/iframe-scaling-with-scroll-expected.png
+++ b/third_party/blink/web_tests/platform/win/fast/frames/iframe-scaling-with-scroll-expected.png
Binary files differ
diff --git a/third_party/blink/web_tests/platform/win/fast/sub-pixel/transformed-iframe-copy-on-scroll-expected.png b/third_party/blink/web_tests/platform/win/fast/sub-pixel/transformed-iframe-copy-on-scroll-expected.png
index e9ba7122..d19d0f5 100644
--- a/third_party/blink/web_tests/platform/win/fast/sub-pixel/transformed-iframe-copy-on-scroll-expected.png
+++ b/third_party/blink/web_tests/platform/win/fast/sub-pixel/transformed-iframe-copy-on-scroll-expected.png
Binary files differ