Changeset 281136 in webkit

Timestamp:

Aug 17, 2021 7:11:22 AM (11 months ago)

Author:

Antti Koivisto

Message:

Incorrect repaint when inline level box style change triggers line height change
​https://bugs.webkit.org/show_bug.cgi?id=229140
<rdar://problem/81980863>

Reviewed by Alan Bujtas.

Source/WebCore:

If an existing block shrinks vertically as a result of layout we fail to invalidate the
old content area for repaint, thus potentially leaving painting artefacts behind.
This is often hidden by the content shift triggering other repaints.

Test: fast/repaint/line-layout-block-shrink.html

• rendering/RenderBlockFlow.cpp:

(WebCore::RenderBlockFlow::layoutModernLines):

Adjust the repaint area to include the content size before the layout.

LayoutTests:

• fast/repaint/line-layout-block-shrink-expected.txt: Added.
• fast/repaint/line-layout-block-shrink.html: Added.

Location:

trunk

Files:

• LayoutTests/ChangeLog (modified) (1 diff)
• LayoutTests/fast/repaint/line-layout-block-shrink-expected.txt (added)
• LayoutTests/fast/repaint/line-layout-block-shrink.html (added)
• Source/WebCore/ChangeLog (modified) (1 diff)
• Source/WebCore/rendering/RenderBlockFlow.cpp (modified) (2 diffs)

trunk/LayoutTests/ChangeLog

@@ +1 @@
+2021-08-17  Antti Koivisto  <antti@apple.com>
+
+        Incorrect repaint when inline level box style change triggers line height change
+        https://bugs.webkit.org/show_bug.cgi?id=229140
+        <rdar://problem/81980863>
+
+        Reviewed by Alan Bujtas.
+
+        * fast/repaint/line-layout-block-shrink-expected.txt: Added.
+        * fast/repaint/line-layout-block-shrink.html: Added.
+
 2021-08-17  Jean-Yves Avenard  <jya@apple.com>
 

trunk/Source/WebCore/ChangeLog

@@ +1 @@
+2021-08-17  Antti Koivisto  <antti@apple.com>
+
+        Incorrect repaint when inline level box style change triggers line height change
+        https://bugs.webkit.org/show_bug.cgi?id=229140
+        <rdar://problem/81980863>
+
+        Reviewed by Alan Bujtas.
+
+        If an existing block shrinks vertically as a result of layout we fail to invalidate the
+        old content area for repaint, thus potentially leaving painting artefacts behind.
+        This is often hidden by the content shift triggering other repaints.
+
+        Test: fast/repaint/line-layout-block-shrink.html
+
+        * rendering/RenderBlockFlow.cpp:
+        (WebCore::RenderBlockFlow::layoutModernLines):
+
+        Adjust the repaint area to include the content size before the layout.
+
 2021-08-17  Philippe Normand  <pnormand@igalia.com>
 

trunk/Source/WebCore/rendering/RenderBlockFlow.cpp

@@ -3732 +3732 @@
     }
 
+    auto contentBoxTop = borderAndPaddingBefore();
+
+    auto computeContentHeight = [&] {
+        if (!hasLines() && hasLineIfEmpty())
+            return lineHeight(true, isHorizontalWritingMode() ? HorizontalLine : VerticalLine, PositionOfInteriorLineBoxes);
+
+        return layoutFormattingContextLineLayout.contentLogicalHeight();
+    };
+
+    auto computeBorderBoxBottom = [&] {
+        auto contentBoxBottom = contentBoxTop + computeContentHeight();
+        return contentBoxBottom + borderAndPaddingAfter();
+    };
+
+    auto oldBorderBoxBottom = computeBorderBoxBottom();
+
     layoutFormattingContextLineLayout.layout();
 
@@ -3737 +3753 @@
         layoutFormattingContextLineLayout.adjustForPagination();
 
-    auto contentHeight = [&] {
-        if (!hasLines() && hasLineIfEmpty())
-            return lineHeight(true, isHorizontalWritingMode() ? HorizontalLine : VerticalLine, PositionOfInteriorLineBoxes);
-        
-        return layoutFormattingContextLineLayout.contentLogicalHeight();
-    }();
-    auto contentBoxTop = borderAndPaddingBefore();
-    auto contentBoxBottom = contentBoxTop + contentHeight;
-    auto borderBoxBottom = contentBoxBottom + borderAndPaddingAfter();
+    auto newBorderBoxBottom = computeBorderBoxBottom();
 
     repaintLogicalTop = contentBoxTop;
-    repaintLogicalBottom = borderBoxBottom;
-    setLogicalHeight(borderBoxBottom);
+    repaintLogicalBottom = std::max(oldBorderBoxBottom, newBorderBoxBottom);
+
+    setLogicalHeight(newBorderBoxBottom);
 }
 #endif