Update PaintLayer::needsPaintPhaseXXX flags when add/remove layer on style change

third_party/WebKit/Source/core/paint/PaintLayer.cpp

Index: third_party/WebKit/Source/core/paint/PaintLayer.cpp
diff --git a/third_party/WebKit/Source/core/paint/PaintLayer.cpp b/third_party/WebKit/Source/core/paint/PaintLayer.cpp
index 5eed81877f073cfb7a536b2120991c542dc3b312..ea7fb5c09c7a28754151381bec080c5fb2124ff5 100644
--- a/third_party/WebKit/Source/core/paint/PaintLayer.cpp
+++ b/third_party/WebKit/Source/core/paint/PaintLayer.cpp
@@ -1257,6 +1257,7 @@ void PaintLayer::removeOnlyThisLayer()
     if (!m_parent)
         return;
 
+    bool didSetPaintInvalidation = false;
     if (!RuntimeEnabledFeatures::slimmingPaintV2Enabled()) {
         DisableCompositingQueryAsserts disabler; // We need the current compositing status.
         if (isPaintInvalidationContainer()) {
@@ -1266,9 +1267,15 @@ void PaintLayer::removeOnlyThisLayer()
             DisablePaintInvalidationStateAsserts disabler;
             layoutObject()->invalidatePaintIncludingNonCompositingDescendants();
             layoutObject()->setShouldDoFullPaintInvalidationIncludingNonCompositingDescendants();
+            didSetPaintInvalidation = true;
         }
     }
 
+    if (!didSetPaintInvalidation && isSelfPaintingLayer()) {

[pdr., 2016/04/08 19:46:07]

Could we just check "if (!needsRepaint() && isSelfPaintingLayer())" ?

[Xianzhu, 2016/04/08 21:30:55]

No. First, needsRepaint flag is set during paint invalidation, and it's always
false before paint invalidation. Second, needsRepaint flag is set when anything
in the layer needs repaint, which doesn't mean the needsPaintPhase flags will be
updated.

+        if (PaintLayer* enclosingSelfPaintingLayer = m_parent->enclosingSelfPaintingLayer())
+            enclosingSelfPaintingLayer->mergeNeedsPaintPhaseFlagsFrom(*this);
+    }
+
     clipper().clearClipRectsIncludingDescendants();
 
     PaintLayer* nextSib = nextSibling();
@@ -1297,6 +1304,19 @@ void PaintLayer::removeOnlyThisLayer()
 
 void PaintLayer::insertOnlyThisLayer()

[pdr., 2016/04/08 19:46:07]

LayoutObject::insertedIntoTree (which calls blink::addLayers) looks similar to
PaintLayer::{insert,remove}OnlyThisLayer(). I think we don't need the merge
flags logic because insertedIntoTree will always cause a paint invalidation...
is that true?

[Xianzhu, 2016/04/08 21:30:56]

Yes.

 {
+    // If the current paint invalidation container is not a stacking context and this object is
+    // stacked content, creating this layer may cause this object and its
+    // descendants to change paint invalidation container. Therefore we must eagerly invalidate
+    // them on the original paint invalidation container before creating the layer.
+    bool didSetPaintInvalidation = false;
+    if (!RuntimeEnabledFeatures::slimmingPaintV2Enabled() && layoutObject()->isRooted() && layoutObject()->styleRef().isStacked()) {
+        const LayoutBoxModelObject& currentPaintInvalidationContainer = layoutObject()->containerForPaintInvalidation();
+        if (!currentPaintInvalidationContainer.styleRef().isStackingContext()) {
+            layoutObject()->invalidatePaintIncludingNonSelfPaintingLayerDescendants(currentPaintInvalidationContainer);
+            didSetPaintInvalidation = true;
+        }
+    }
+
     if (!m_parent && layoutObject()->parent()) {
         // We need to connect ourselves when our layoutObject() has a parent.
         // Find our enclosingLayer and add ourselves.
@@ -1306,6 +1326,11 @@ void PaintLayer::insertOnlyThisLayer()
         parentLayer->addChild(this, beforeChild);
     }
 
+    if (!didSetPaintInvalidation && isSelfPaintingLayer()) {
+        if (PaintLayer* enclosingSelfPaintingLayer = m_parent->enclosingSelfPaintingLayer())

[pdr., 2016/04/08 19:46:07]

Similar to my comment in LayoutBoxModelObject::createLayer, will
"m_parent->enclosingSelfPaintingLayer()" always be the original enclosing self
painting layer of the layout object before it gained a layer?

[Xianzhu, 2016/04/08 21:30:55]

Yes, because here it's using m_parent->.

+            mergeNeedsPaintPhaseFlagsFrom(*enclosingSelfPaintingLayer);
+    }
+
     // Remove all descendant layers from the hierarchy and add them to the new position.
     for (LayoutObject* curr = layoutObject()->slowFirstChild(); curr; curr = curr->nextSibling())
         curr->moveLayers(m_parent, this);