Changeset 269895 in webkit

Timestamp:

Nov 17, 2020 12:28:31 AM (3 years ago)

Author:

timothy_horton@apple.com

Message:

REGRESSION (r269824): YouTube media control bar sometimes flickers
​https://bugs.webkit.org/show_bug.cgi?id=219017
<rdar://problem/71454799>

Reviewed by Simon Fraser.

Source/WebKit:

Test: compositing/repaint/transparent-layer-repaint.html

• Shared/RemoteLayerTree/RemoteLayerBackingStore.mm:

(WebKit::RemoteLayerBackingStore::display):
I accidentally lost the Copy composite operator in r269824, causing
the repaint copy-forward to blend instead of just copying.
This wreaks havoc on layers with contents with colors that have 0 < alpha < 1,
because every repaint means the colors intensify.

LayoutTests:

• compositing/repaint/transparent-layer-repaint-expected.html: Added.
• compositing/repaint/transparent-layer-repaint.html: Added.

Add a test that:

• repaints a backingstoreful compositing layer
• more than once
• in a small enough area that we use partial repaint
• with partially-transparent pixels

And then ensures that the background of that layer (the non-repainted part)
remains the color that it should.

Location:

trunk

Files:

• LayoutTests/ChangeLog (modified) (1 diff)
• LayoutTests/compositing/repaint/transparent-layer-repaint-expected.html (added)
• LayoutTests/compositing/repaint/transparent-layer-repaint.html (added)
• Source/WebKit/ChangeLog (modified) (1 diff)
• Source/WebKit/Shared/RemoteLayerTree/RemoteLayerBackingStore.mm (modified) (1 diff)

trunk/LayoutTests/ChangeLog

@@ +1 @@
+2020-11-17  Tim Horton  <timothy_horton@apple.com>
+
+        REGRESSION (r269824): YouTube media control bar sometimes flickers
+        https://bugs.webkit.org/show_bug.cgi?id=219017
+        <rdar://problem/71454799>
+
+        Reviewed by Simon Fraser.
+
+        * compositing/repaint/transparent-layer-repaint-expected.html: Added.
+        * compositing/repaint/transparent-layer-repaint.html: Added.
+        Add a test that:
+            - repaints a backingstoreful compositing layer
+            - more than once
+            - in a small enough area that we use partial repaint
+            - with partially-transparent pixels
+
+        And then ensures that the background of that layer (the non-repainted part)
+        remains the color that it should.
+
 2020-11-17  Rob Buis  <rbuis@igalia.com>
 

trunk/Source/WebKit/ChangeLog

@@ +1 @@
+2020-11-17  Tim Horton  <timothy_horton@apple.com>
+
+        REGRESSION (r269824): YouTube media control bar sometimes flickers
+        https://bugs.webkit.org/show_bug.cgi?id=219017
+        <rdar://problem/71454799>
+
+        Reviewed by Simon Fraser.
+
+        Test: compositing/repaint/transparent-layer-repaint.html
+
+        * Shared/RemoteLayerTree/RemoteLayerBackingStore.mm:
+        (WebKit::RemoteLayerBackingStore::display):
+        I accidentally lost the Copy composite operator in r269824, causing
+        the repaint copy-forward to blend instead of just copying.
+        This wreaks havoc on layers with contents with colors that have 0 < alpha < 1,
+        because every repaint means the colors intensify.
+
 2020-11-16  Brent Fulgham  <bfulgham@apple.com>
 

trunk/Source/WebKit/Shared/RemoteLayerTree/RemoteLayerBackingStore.mm

@@ -252 +252 @@
     if (!m_dirtyRegion.contains(layerBounds)) {
         ASSERT(m_backBuffer.imageBuffer);
-        context.drawImageBuffer(*m_backBuffer.imageBuffer, { 0, 0 });
+        context.drawImageBuffer(*m_backBuffer.imageBuffer, { 0, 0 }, { WebCore::CompositeOperator::Copy });
     }