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      1 // Copyright 2014 The Chromium Authors. All rights reserved.
      2 // Use of this source code is governed by a BSD-style license that can be
      3 // found in the LICENSE file.
      4 
      5 #include "config.h"
      6 #include "core/rendering/compositing/CompositingReasonFinder.h"
      7 
      8 #include "core/CSSPropertyNames.h"
      9 #include "core/dom/Document.h"
     10 #include "core/frame/FrameView.h"
     11 #include "core/frame/Settings.h"
     12 #include "core/page/Page.h"
     13 #include "core/rendering/RenderView.h"
     14 #include "core/rendering/compositing/RenderLayerCompositor.h"
     15 
     16 namespace blink {
     17 
     18 CompositingReasonFinder::CompositingReasonFinder(RenderView& renderView)
     19     : m_renderView(renderView)
     20     , m_compositingTriggers(static_cast<CompositingTriggerFlags>(AllCompositingTriggers))
     21 {
     22     updateTriggers();
     23 }
     24 
     25 void CompositingReasonFinder::updateTriggers()
     26 {
     27     m_compositingTriggers = 0;
     28 
     29     Settings& settings = m_renderView.document().page()->settings();
     30     if (settings.preferCompositingToLCDTextEnabled()) {
     31         m_compositingTriggers |= ScrollableInnerFrameTrigger;
     32         m_compositingTriggers |= OverflowScrollTrigger;
     33         m_compositingTriggers |= ViewportConstrainedPositionedTrigger;
     34     }
     35 }
     36 
     37 bool CompositingReasonFinder::hasOverflowScrollTrigger() const
     38 {
     39     return m_compositingTriggers & OverflowScrollTrigger;
     40 }
     41 
     42 bool CompositingReasonFinder::isMainFrame() const
     43 {
     44     // FIXME: LocalFrame::isMainFrame() is probably better.
     45     return !m_renderView.document().ownerElement();
     46 }
     47 
     48 CompositingReasons CompositingReasonFinder::directReasons(const RenderLayer* layer) const
     49 {
     50     ASSERT(potentialCompositingReasonsFromStyle(layer->renderer()) == layer->potentialCompositingReasonsFromStyle());
     51     CompositingReasons styleDeterminedDirectCompositingReasons = layer->potentialCompositingReasonsFromStyle() & CompositingReasonComboAllDirectStyleDeterminedReasons;
     52     return styleDeterminedDirectCompositingReasons | nonStyleDeterminedDirectReasons(layer);
     53 }
     54 
     55 // This information doesn't appear to be incorporated into CompositingReasons.
     56 bool CompositingReasonFinder::requiresCompositingForScrollableFrame() const
     57 {
     58     // Need this done first to determine overflow.
     59     ASSERT(!m_renderView.needsLayout());
     60     if (isMainFrame())
     61         return false;
     62 
     63     if (!(m_compositingTriggers & ScrollableInnerFrameTrigger))
     64         return false;
     65 
     66     return m_renderView.frameView()->isScrollable();
     67 }
     68 
     69 CompositingReasons CompositingReasonFinder::potentialCompositingReasonsFromStyle(RenderObject* renderer) const
     70 {
     71     CompositingReasons reasons = CompositingReasonNone;
     72 
     73     RenderStyle* style = renderer->style();
     74 
     75     if (requiresCompositingForTransform(renderer))
     76         reasons |= CompositingReason3DTransform;
     77 
     78     if (style->backfaceVisibility() == BackfaceVisibilityHidden)
     79         reasons |= CompositingReasonBackfaceVisibilityHidden;
     80 
     81     if (requiresCompositingForAnimation(style))
     82         reasons |= CompositingReasonActiveAnimation;
     83 
     84     if (style->hasWillChangeCompositingHint() && !style->subtreeWillChangeContents())
     85         reasons |= CompositingReasonWillChangeCompositingHint;
     86 
     87     if (style->hasInlineTransform())
     88         reasons |= CompositingReasonInlineTransform;
     89 
     90     if (style->transformStyle3D() == TransformStyle3DPreserve3D)
     91         reasons |= CompositingReasonPreserve3DWith3DDescendants;
     92 
     93     if (style->hasPerspective())
     94         reasons |= CompositingReasonPerspectiveWith3DDescendants;
     95 
     96     // If the implementation of createsGroup changes, we need to be aware of that in this part of code.
     97     ASSERT((renderer->isTransparent() || renderer->hasMask() || renderer->hasFilter() || renderer->hasBlendMode()) == renderer->createsGroup());
     98 
     99     if (style->hasMask())
    100         reasons |= CompositingReasonMaskWithCompositedDescendants;
    101 
    102     if (style->hasFilter())
    103         reasons |= CompositingReasonFilterWithCompositedDescendants;
    104 
    105     // See RenderLayer::updateTransform for an explanation of why we check both.
    106     if (renderer->hasTransform() && style->hasTransform())
    107         reasons |= CompositingReasonTransformWithCompositedDescendants;
    108 
    109     if (renderer->isTransparent())
    110         reasons |= CompositingReasonOpacityWithCompositedDescendants;
    111 
    112     if (renderer->hasBlendMode())
    113         reasons |= CompositingReasonBlendingWithCompositedDescendants;
    114 
    115     if (renderer->hasReflection())
    116         reasons |= CompositingReasonReflectionWithCompositedDescendants;
    117 
    118     ASSERT(!(reasons & ~CompositingReasonComboAllStyleDeterminedReasons));
    119     return reasons;
    120 }
    121 
    122 bool CompositingReasonFinder::requiresCompositingForTransform(RenderObject* renderer) const
    123 {
    124     // Note that we ask the renderer if it has a transform, because the style may have transforms,
    125     // but the renderer may be an inline that doesn't suppport them.
    126     return renderer->hasTransform() && renderer->style()->transform().has3DOperation();
    127 }
    128 
    129 CompositingReasons CompositingReasonFinder::nonStyleDeterminedDirectReasons(const RenderLayer* layer) const
    130 {
    131     CompositingReasons directReasons = CompositingReasonNone;
    132     RenderObject* renderer = layer->renderer();
    133 
    134     if (hasOverflowScrollTrigger()) {
    135         if (layer->clipParent())
    136             directReasons |= CompositingReasonOutOfFlowClipping;
    137 
    138         if (const RenderLayer* scrollingAncestor = layer->ancestorScrollingLayer()) {
    139             if (scrollingAncestor->needsCompositedScrolling() && layer->scrollParent())
    140                 directReasons |= CompositingReasonOverflowScrollingParent;
    141         }
    142 
    143         if (layer->needsCompositedScrolling())
    144             directReasons |= CompositingReasonOverflowScrollingTouch;
    145     }
    146 
    147     if (requiresCompositingForPositionFixed(layer))
    148         directReasons |= CompositingReasonPositionFixed;
    149 
    150     directReasons |= renderer->additionalCompositingReasons();
    151 
    152     ASSERT(!(directReasons & CompositingReasonComboAllStyleDeterminedReasons));
    153     return directReasons;
    154 }
    155 
    156 bool CompositingReasonFinder::requiresCompositingForAnimation(RenderStyle* style) const
    157 {
    158     if (style->subtreeWillChangeContents())
    159         return style->isRunningAnimationOnCompositor();
    160 
    161     return style->shouldCompositeForCurrentAnimations();
    162 }
    163 
    164 bool CompositingReasonFinder::requiresCompositingForPositionFixed(const RenderLayer* layer) const
    165 {
    166     if (!(m_compositingTriggers & ViewportConstrainedPositionedTrigger))
    167         return false;
    168     // Don't promote fixed position elements that are descendants of a non-view container, e.g. transformed elements.
    169     // They will stay fixed wrt the container rather than the enclosing frame.
    170     return layer->scrollsWithViewport() && m_renderView.frameView()->isScrollable();
    171 }
    172 
    173 }
    174