Replace LayoutObject::skipInvalidationWhenLaidOutChildren() with paintedOutputOfObjectHasNoEffect

third_party/WebKit/Source/core/layout/LayoutObject.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2000 Dirk Mueller (mueller@kde.org)
  *           (C) 2004 Allan Sandfeld Jensen (kde@carewolf.com)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2011 Apple Inc. All rights reserved.
  * Copyright (C) 2009 Google Inc. All rights reserved.
  * Copyright (C) 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  *
  * This library is free software; you can redistribute it and/or
@@ skipping 666 matching lines @@
     // See if we have the thread cached because we're in the middle of layout.
     if (LayoutState* layoutState = view()->layoutState()) {
         if (LayoutFlowThread* flowThread = layoutState->flowThread())
             return flowThread;
     }
 
     // Not in the middle of layout so have to find the thread the slow way.
     return LayoutFlowThread::locateFlowThreadContainingBlockOf(*this);
 }
 
-bool LayoutObject::skipInvalidationWhenLaidOutChildren() const
-{
-    if (!m_bitfields.neededLayoutBecauseOfChildren())
-        return false;
-
-    // SVG layoutObjects need to be invalidated when their children are laid out.
-    // LayoutBlocks with line boxes are responsible to invalidate them so we can't ignore them.
-    if (isSVG() || (isLayoutBlockFlow() && toLayoutBlockFlow(this)->firstLineBox()))
-        return false;

[Xianzhu, 2016/08/03 19:56:36]

The "isLayoutBlockFlow() && toLayoutBlockFlow(this)->firstLineBox()" condition
is removed because LayoutBlockFlow no longer invalidate for line boxes, but
LayoutInline and LayoutText do.

-
-    // In case scrollbars got repositioned (which will typically happen if the layout object got
-    // resized), we cannot skip invalidation.
-    if (hasNonCompositedScrollbars())
-        return false;
-
-    // We can't detect whether a plugin has box effects, so disable this optimization for that case.
-    if (isEmbeddedObject())
-        return false;
-
-    return !hasBoxEffect();
-}
-
 static inline bool objectIsRelayoutBoundary(const LayoutObject* object)
 {
     // FIXME: In future it may be possible to broaden these conditions in order to improve performance.
     if (object->isTextControl())
         return true;
 
     if (object->isSVGRoot())
         return true;
 
     // Table parts can't be relayout roots since the table is responsible for layouting all the parts.
@@ skipping 604 matching lines @@
             return;
         selectionPaintInvalidationMap = new SelectionPaintInvalidationMap();
     }
 
     if (selectionRect.isEmpty())
         selectionPaintInvalidationMap->remove(this);
     else
         selectionPaintInvalidationMap->set(this, selectionRect);
 }
 
-// TODO(wangxianzhu): Remove this for slimming paint v2 because we won't care about paint invalidation rects.
 inline void LayoutObject::invalidateSelectionIfNeeded(const LayoutBoxModelObject& paintInvalidationContainer, const PaintInvalidationState& paintInvalidationState, PaintInvalidationReason invalidationReason)
 {
     // Update selection rect when we are doing full invalidation (in case that the object is moved, composite status changed, etc.)
     // or shouldInvalidationSelection is set (in case that the selection itself changed).
     bool fullInvalidation = isFullPaintInvalidationReason(invalidationReason);
     if (!fullInvalidation && !shouldInvalidateSelection())
         return;
 
     LayoutRect oldSelectionRect = previousSelectionRectForPaintInvalidation();
     LayoutRect newSelectionRect = localSelectionRect();
     if (!newSelectionRect.isEmpty()) {
         paintInvalidationState.mapLocalRectToPaintInvalidationBacking(newSelectionRect);
 
         // Composited scrolling should not be included in the bounds and position tracking, because the graphics layer backing the scroller
         // does not move on scroll.
         if (compositedScrollsWithRespectTo(paintInvalidationContainer)) {
             LayoutSize inverseOffset(toLayoutBox(&paintInvalidationContainer)->scrolledContentOffset());
             newSelectionRect.move(inverseOffset);
         }
     }
 
     setPreviousSelectionRectForPaintInvalidation(newSelectionRect);
 
-    // TODO(wangxianzhu): Combine the following two conditions when removing LayoutView::doingFullPaintInvalidation().
-    if (!fullInvalidation)
+    if (!fullInvalidation) {
         fullyInvalidatePaint(paintInvalidationContainer, PaintInvalidationSelection, oldSelectionRect, newSelectionRect);
-    if (shouldInvalidateSelection())
         invalidateDisplayItemClientsWithPaintInvalidationState(paintInvalidationState, PaintInvalidationSelection);
+    }
 }
 
 PaintInvalidationReason LayoutObject::invalidatePaintIfNeeded(const PaintInvalidationState& paintInvalidationState)
 {
     ASSERT(&paintInvalidationState.currentObject() == this);
 
     if (styleRef().hasOutline()) {
         PaintLayer& layer = paintInvalidationState.paintingLayer();
         if (layer.layoutObject() != this)
             layer.setNeedsPaintPhaseDescendantOutlines();
@@ skipping 44 matching lines @@
         invalidationReason = PaintInvalidationBackgroundObscurationChange;
     m_bitfields.setLastBoxDecorationBackgroundObscured(boxDecorationBackgroundObscured);
 
     if (invalidationReason == PaintInvalidationNone) {
         // TODO(trchen): Currently we don't keep track of paint offset of layout objects.
         // There are corner cases that the display items need to be invalidated for paint offset
         // mutation, but incurs no pixel difference (i.e. bounds stay the same) so no rect-based
         // invalidation is issued. See crbug.com/508383 and crbug.com/515977.
         // This is a workaround to force display items to update paint offset.
         if (!RuntimeEnabledFeatures::slimmingPaintInvalidationEnabled() && paintInvalidationState.forcedSubtreeInvalidationCheckingWithinContainer())
-            invalidateDisplayItemClientsWithPaintInvalidationState(paintInvalidationState, invalidationReason);
+            invalidateDisplayItemClientsWithPaintInvalidationState(paintInvalidationState, PaintInvalidationLocationChange);
 
         return invalidationReason;
     }
 
     if (invalidationReason == PaintInvalidationIncremental)
         incrementallyInvalidatePaint(paintInvalidationContainer, oldBounds, newBounds, newLocation);
     else
         fullyInvalidatePaint(paintInvalidationContainer, invalidationReason, oldBounds, newBounds);
 
     invalidateDisplayItemClientsWithPaintInvalidationState(paintInvalidationState, invalidationReason);
     return invalidationReason;
 }
 
 PaintInvalidationReason LayoutObject::getPaintInvalidationReason(const PaintInvalidationState& paintInvalidationState,
     const LayoutRect& oldBounds, const LayoutPoint& oldPositionFromPaintInvalidationBacking,
     const LayoutRect& newBounds, const LayoutPoint& newPositionFromPaintInvalidationBacking) const
 {
     if (paintInvalidationState.forcedSubtreeFullInvalidationWithinContainer())
         return PaintInvalidationSubtree;
 
     if (shouldDoFullPaintInvalidation())
         return m_bitfields.fullPaintInvalidationReason();
 
+    if (canSkipUnforcedPaintInvalidation())

[chrishtr, 2016/08/03 20:33:51]

What is the main use case of this optimization? Is it avoiding invalidation on
the body element when resizing?

[Xianzhu, 2016/08/03 21:30:35]

It avoids invalidation if the geometry change affects nothing of this object's
painting. This includes the case of resizing body element (having no own
content).

Added a comment.

[chrishtr, 2016/08/03 21:34:56]

How about restricting the optimization to the body element?

[Xianzhu, 2016/08/03 22:09:02]

This optimization also reduces unnecessary rasterization invalidations for other
big empty objects or big objects that have children but paint nothing for
itself.

For example,

<body>
<div id="container">
  ...
</div>
</body>

container.appendChild(someChild with small width);

we only need to invalidate the area of the new child. Without the optimization,
we also need to invalidate the container (width-of-body x height-of-new-child).

+        return PaintInvalidationNone;
+
     // The outline may change shape because of position change of descendants. For simplicity,
     // just force full paint invalidation if this object is marked for checking paint invalidation
     // for any reason.
     if (styleRef().hasOutline())
         return PaintInvalidationOutline;
 
     bool locationChanged = newPositionFromPaintInvalidationBacking != oldPositionFromPaintInvalidationBacking;
 
     // If the bounds are the same then we know that none of the statements below
     // can match, so we can early out.
     if (oldBounds == newBounds)
         return locationChanged && !oldBounds.isEmpty() ? PaintInvalidationLocationChange : PaintInvalidationNone;
 
     // If we shifted, we don't know the exact reason so we are conservative and trigger a full invalidation. Shifting could
     // be caused by some layout property (left / top) or some in-flow layoutObject inserted / removed before us in the tree.
     if (newBounds.location() != oldBounds.location())
         return PaintInvalidationBoundsChange;
 
-    // This covers the case where we mark containing blocks for layout
-    // and they change size but don't have anything to paint. This is
-    // a pretty common case for <body> as we add / remove children
-    // (and the default background is done by FrameView).
-    if (!RuntimeEnabledFeatures::slimmingPaintV2Enabled() && skipInvalidationWhenLaidOutChildren())
-        return PaintInvalidationNone;
-
     // If the size is zero on one of our bounds then we know we're going to have
     // to do a full invalidation of either old bounds or new bounds. If we fall
     // into the incremental invalidation we'll issue two invalidations instead
     // of one.
     if (oldBounds.isEmpty())
         return PaintInvalidationBecameVisible;
     if (newBounds.isEmpty())
         return PaintInvalidationBecameInvisible;
 
     if (locationChanged)
@@ skipping 1966 matching lines @@
     setMayNeedPaintInvalidation();
 }
 
 void LayoutObject::clearPaintInvalidationFlags(const PaintInvalidationState& paintInvalidationState)
 {
     // paintInvalidationStateIsDirty should be kept in sync with the
     // booleans that are cleared below.
     ASSERT(!shouldCheckForPaintInvalidationRegardlessOfPaintInvalidationState() || paintInvalidationStateIsDirty());
     clearShouldDoFullPaintInvalidation();
     m_bitfields.setChildShouldCheckForPaintInvalidation(false);
-    m_bitfields.setNeededLayoutBecauseOfChildren(false);
     m_bitfields.setMayNeedPaintInvalidation(false);
     m_bitfields.setMayNeedPaintInvalidationSubtree(false);
     m_bitfields.setShouldInvalidateSelection(false);
 }
 
 bool LayoutObject::isAllowedToModifyLayoutTreeStructure(Document& document)
 {
     return DeprecatedDisableModifyLayoutTreeStructureAsserts::canModifyLayoutTreeStateInAnyState()
         || document.lifecycle().stateAllowsLayoutTreeMutations();
 }
@@ skipping 202 matching lines @@
         const blink::LayoutObject* root = object1;
         while (root->parent())
             root = root->parent();
         root->showLayoutTreeAndMark(object1, "*", object2, "-", 0);
     } else {
         WTFLogAlways("%s", "Cannot showLayoutTree. Root is (nil)");
     }
 }
 
 #endif