Cherry-pick 126e5bd39128. rdar://120666136

Cherry-pick 272394@main (5ce41d8). rdar://120666136 Wikipedia video control icon backgrounds flicker. https://bugs.webkit.org/show_bug.cgi?id=266726 <rdar://119868478> Reviewed by Simon Fraser. The previous code always required a full repaint of the layer whenever a buffer was allocated, so the copy-forward code didn't run on the second paint of a layer. This meant the copy-forward code, and the 'buffer is already clear' optimization were mutually exclusive. The new code uses copy-forward and partial repaints whenever possible, even if the front buffer was newly allocated (or existing, but purged). The copy-forward code tries to only copy pixels that won't be re-drawn this frame, but is rounded out to a single rectangle, not a complex region. If the copy-forwards ends up copying pixels that we'll also drawn this frame, we can no longer consider the buffer to be 'clear' and have to manually clear the paint region. * LayoutTests/compositing/repaint/copy-forward-clear-rect-expected.html: Added. * LayoutTests/compositing/repaint/copy-forward-clear-rect.html: Added. * Source/WebKit/GPUProcess/graphics/RemoteImageBufferSet.cpp: (WebKit::RemoteImageBufferSet::prepareBufferForDisplay): Canonical link: https://commits.webkit.org/272394@main Canonical link: https://commits.webkit.org/271831.79@safari-7619.0.1-branch
WebKit · Jan 10, 2024 · 0abaf26 · 0abaf26
1 parent 809cefc
commit 0abaf26
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diff --git a/LayoutTests/compositing/repaint/copy-forward-clear-rect-expected.html b/LayoutTests/compositing/repaint/copy-forward-clear-rect-expected.html
@@ -0,0 +1,25 @@
+<!DOCTYPE html>
+
+<html>
+<head>
+    <style>
+        #first {
+            width: 500px;
+            height: 500px;
+            transform: translate3d(0, 0, 0);
+            background: rgba(222, 0, 0, 0.4);
+        }
+        #inner {
+            left: 50px;
+            top: 50px;
+            width: 50px;
+            height: 50px;
+            position: absolute;
+            background: rgba(0, 40, 40, 0.5);
+        }
+    </style>
+</head>
+<body>
+    <div id="first"><div id="inner"></div></div>
+</body>
+</html>
diff --git a/LayoutTests/compositing/repaint/copy-forward-clear-rect.html b/LayoutTests/compositing/repaint/copy-forward-clear-rect.html
@@ -0,0 +1,45 @@
+<!DOCTYPE html>
+
+<html>
+<head>
+    <script src="../../resources/ui-helper.js"></script>
+    <style>
+        #first {
+            width: 500px;
+            height: 500px;
+            transform: translate3d(0, 0, 0);
+            background: rgba(222, 0, 0, 0.4);
+        }
+        #inner {
+            width: 50px;
+            height: 50px;
+            position: absolute;
+            background: rgba(0, 40, 40, 0.5);
+        }
+    </style>
+    <script>
+        if (window.testRunner) {
+            testRunner.waitUntilDone();
+            if (testRunner.dontForceRepaint)
+                testRunner.dontForceRepaint();
+        }
+        async function doTest()
+        {
+            await UIHelper.renderingUpdate();
+
+            inner.style.left = "50px";
+            inner.style.top = "50px";
+
+            await UIHelper.renderingUpdate();
+            await UIHelper.renderingUpdate();
+
+            if (window.testRunner)
+                testRunner.notifyDone();
+        }
+        window.addEventListener('load', doTest, false);
+    </script>
+</head>
+<body>
+    <div id="first"><div id="inner"></div></div>
+</body>
+</html>
diff --git a/Source/WebKit/GPUProcess/graphics/RemoteImageBufferSet.cpp b/Source/WebKit/GPUProcess/graphics/RemoteImageBufferSet.cpp
@@ -188,10 +188,11 @@ void RemoteImageBufferSet::prepareBufferForDisplay(const WebCore::Region& dirtyR
     GraphicsContext& context = m_frontBuffer->context();
     context.resetClip();
 
+    IntRect copyRect;
     if (m_previousFrontBuffer && m_frontBuffer != m_previousFrontBuffer && !dirtyRegion.contains(layerBounds)) {
         Region copyRegion(m_previouslyPaintedRect ? *m_previouslyPaintedRect : layerBounds);
         copyRegion.subtract(dirtyRegion);
-        IntRect copyRect = copyRegion.bounds();
+        copyRect = copyRegion.bounds();
         if (!copyRect.isEmpty())
             m_frontBuffer->context().drawImageBuffer(*m_previousFrontBuffer, copyRect, copyRect, { CompositeOperator::Copy });
     }
@@ -212,6 +213,11 @@ void RemoteImageBufferSet::prepareBufferForDisplay(const WebCore::Region& dirtyR
         scaledRect = enclosingIntRect(scaledRect);
         scaledRect.scale(1 / m_resolutionScale);
         paintingRects.append(scaledRect);
+
+        // If the copy-forward touched pixels that are about to be painted, then they
+        // won't be 'clear' any more.
+        if (copyRect.intersects(scaledRect))
+            m_frontBufferIsCleared = false;
     }
 
     if (paintingRects.size() == 1)