Repaint on interest rect change

third_party/WebKit/Source/core/layout/compositing/CompositedLayerMapping.cpp

Index: third_party/WebKit/Source/core/layout/compositing/CompositedLayerMapping.cpp
diff --git a/third_party/WebKit/Source/core/layout/compositing/CompositedLayerMapping.cpp b/third_party/WebKit/Source/core/layout/compositing/CompositedLayerMapping.cpp
index 078055e5331926713b4732101823e2956efab40a..3298f4000c067c71c40db46cbbbdec0915b95b92 100644
--- a/third_party/WebKit/Source/core/layout/compositing/CompositedLayerMapping.cpp
+++ b/third_party/WebKit/Source/core/layout/compositing/CompositedLayerMapping.cpp
@@ -2202,26 +2202,47 @@ IntRect CompositedLayerMapping::computeInterestRect(const GraphicsLayer* graphic
     return localInterestRect;
 }
 
-void CompositedLayerMapping::paintContentsIfNeeded(const GraphicsLayer* graphicsLayer, GraphicsContext& context, GraphicsLayerPaintingPhase graphicsLayerPaintingPhase) const
+static bool changedSufficiently(int newValue, int previousValue, int baseValue)
 {
-    ASSERT(RuntimeEnabledFeatures::slimmingPaintSynchronizedPaintingEnabled());
+    return std::abs(newValue - previousValue) * 16 < baseValue;
+}
 
-    // TODO(chrishtr): Also paint if the interest rect has changed sufficiently.
-    if (!m_owningLayer.needsRepaint()) {
-        context.paintController().createAndAppend<CachedDisplayItem>(*this, DisplayItem::CachedDisplayItemList);
-        return;
-    }
+static bool interestRectChangeNeedsRepaint(const IntRect& newInterestRect, const IntRect& previousInterestRect)

[chrishtr, 2015/10/28 21:03:54]

This is a little different than what DisplayListRecordingSource does. We should
just copy the logic exactly.

Also, rename to interestChangedEnoughToNeedRepaint.

[Xianzhu, 2015/10/29 01:55:09]

Done.

+{
+    if (previousInterestRect.contains(newInterestRect))
+        return false;
+    return changedSufficiently(newInterestRect.x(), previousInterestRect.x(), previousInterestRect.width())
+        || changedSufficiently(newInterestRect.y(), previousInterestRect.y(), previousInterestRect.height())
+        || changedSufficiently(newInterestRect.maxX(), previousInterestRect.maxX(), previousInterestRect.width())
+        || changedSufficiently(newInterestRect.maxY(), previousInterestRect.maxY(), previousInterestRect.height());
+}
+
+void CompositedLayerMapping::paintContents(const GraphicsLayer* graphicsLayer, GraphicsContext& context, GraphicsLayerPaintingPhase graphicsLayerPaintingPhase, const IntRect* interestRect) const
+{
+    IntRect defaultInterestRect;
+    if (RuntimeEnabledFeatures::slimmingPaintSynchronizedPaintingEnabled()) {
+        if (!interestRect) {
+            if (graphicsLayer == m_graphicsLayer || graphicsLayer == m_squashingLayer)
+                defaultInterestRect = computeInterestRect(graphicsLayer, m_owningLayer.layoutObject());
+            else
+                defaultInterestRect = enclosingIntRect(FloatRect(FloatPoint(), graphicsLayer->size()));
+            interestRect = &defaultInterestRect;
+        }
 
-    IntRect interestRect;
-    if (graphicsLayer == m_graphicsLayer || graphicsLayer == m_squashingLayer)
-        interestRect = computeInterestRect(graphicsLayer, m_owningLayer.layoutObject());
-    else
-        interestRect = enclosingIntRect(FloatRect(FloatPoint(), graphicsLayer->size()));
+        if (!m_owningLayer.needsRepaint()
+            && context.paintController().clientCacheIsValid(m_owningLayer.displayItemClient())
+            && !interestRectChangeNeedsRepaint(*interestRect, m_previousPaintInterestRect)) {
+            context.paintController().createAndAppend<CachedDisplayItem>(*this, DisplayItem::CachedDisplayItemList);
+            return;
+
+        m_previousPaintInterestRect = *interestRect;
+    }
 
-    paintContents(graphicsLayer, context, graphicsLayerPaintingPhase, interestRect);
+    ASSERT(interestRect);
+    paintContentsInternal(graphicsLayer, context, graphicsLayerPaintingPhase, *interestRect);
 }
 
-void CompositedLayerMapping::paintContents(const GraphicsLayer* graphicsLayer, GraphicsContext& context, GraphicsLayerPaintingPhase graphicsLayerPaintingPhase, const IntRect& interestRect) const
+void CompositedLayerMapping::paintContentsInternal(const GraphicsLayer* graphicsLayer, GraphicsContext& context, GraphicsLayerPaintingPhase graphicsLayerPaintingPhase, const IntRect& interestRect) const
 {
     // https://code.google.com/p/chromium/issues/detail?id=343772
     DisableCompositingQueryAsserts disabler;