Don't ever check for fragment intersections when painting ancestor cl…

…ipping masks, or clip to the compositing container. It doesn't make sense to do this, because (a) it doesn't achieve anything, and similar optimizations are already implemented in CompositedLayerMapping, and (b) it is not quite correct, because the overflow clip of the stacking ancestor is applied before checking fragment intersections, which can be wrong if the descendant is not clipped. This latter condition caused issue 747364. Bug: 749760, 747364 Cq-Include-Trybots: master.tryserver.chromium.linux:linux_layout_tests_slimming_paint_v2 Change-Id: I1485cc86c2f0dfc222171d1b53eb27f083d2c2c8 Reviewed-on: https://chromium-review.googlesource.com/589825 Reviewed-by: Stephen Chenney <schenney@chromium.org> Commit-Queue: Chris Harrelson <chrishtr@chromium.org> Cr-Commit-Position: refs/heads/master@{#490502}
Denger-Network · Jul 28, 2017 · a1fa33f · a1fa33f
1 parent 4735fae
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Showing 4 changed files with 19 additions and 3 deletions.
diff --git a/third_party/WebKit/LayoutTests/TestExpectations b/third_party/WebKit/LayoutTests/TestExpectations
@@ -1020,6 +1020,9 @@ crbug.com/492664 external/wpt/css/css-writing-modes-3/clip-rect-vrl-006.xht [ Fa
 crbug.com/492664 external/wpt/css/css-writing-modes-3/clip-rect-vrl-008.xht [ Failure ]
 crbug.com/492664 external/wpt/css/css-writing-modes-3/line-box-direction-vrl-009.xht [ Failure ]
 
+crbug.com/749760 compositing/overflow/relpos-under-abspos-border-radius.html [ Failure ]
+crbug.com/749760 virtual/prefer_compositing_to_lcd_text/compositing/overflow/relpos-under-abspos-border-radius.html [ Failure ]
+
 crbug.com/637255 [ Win10 ] media/video-transformed.html [ Pass Failure ]
 
 # These tests pass but images do not match because tests are stricter than the spec.

diff --git a/...y/WebKit/LayoutTests/compositing/overflow/relpos-under-abspos-border-radius-expected.html b/...y/WebKit/LayoutTests/compositing/overflow/relpos-under-abspos-border-radius-expected.html
@@ -0,0 +1,5 @@
+<!DOCTYPE html>
+<div id=border-radius style="border-radius: 5px; overflow: hidden; position: absolute;  width: 100px; height: 100px; top: 0px; left: 0px; backface-visibility: hidden; ">
+  <div id=child style="width: 25px; height: 25px; position: relative; background: green; ">
+  </div>
+</div>
diff --git a/third_party/WebKit/LayoutTests/compositing/overflow/relpos-under-abspos-border-radius.html b/third_party/WebKit/LayoutTests/compositing/overflow/relpos-under-abspos-border-radius.html
@@ -0,0 +1,8 @@
+<!DOCTYPE html>
+<!-- Passes if there is a rounded green rect at the top left -->
+<div id=root style="margin-left: 200px; margin-top: 200px; width: 20px; height: 20px; opacity: 0.99999; overflow: hidden;">
+  <div id=border-radius style="border-radius: 5px; overflow: hidden; position: absolute;  width: 100px; height: 100px; top: 0px; left: 0px; backface-visibility: hidden; ">
+     <div id=child style="width: 25px; height: 25px; position: relative; background: green; ">
+     </div>
+  </div>
+</div>
diff --git a/third_party/WebKit/Source/core/paint/PaintLayerPainter.cpp b/third_party/WebKit/Source/core/paint/PaintLayerPainter.cpp
@@ -434,6 +434,8 @@ PaintResult PaintLayerPainter::PaintLayerContents(
       paint_layer_.ConvertToLayerCoords(local_painting_info.root_layer,
                                         offset_to_clipper);
       local_painting_info.paint_dirty_rect.MoveBy(offset_to_clipper);
+      // Overflow clip of the compositing container is irrelevant.
+      respect_overflow_clip = kIgnoreOverflowClip;
     }
 
     // TODO(trchen): We haven't decided how to handle visual fragmentation with
@@ -509,9 +511,7 @@ PaintResult PaintLayerPainter::PaintLayerContents(
         fragment.foreground_rect.Move(negative_offset);
         fragment.pagination_offset.Move(negative_offset);
       }
-    }
-
-    if (should_paint_content) {
+    } else if (should_paint_content) {
       // TODO(wangxianzhu): This is for old slow scrolling. Implement similar
       // optimization for slimming paint v2.
       should_paint_content = AtLeastOneFragmentIntersectsDamageRect(