[CSS Blending] Implement mix-blend-mode in software.

Source/core/rendering/RenderLayer.cpp

 /*
  * Copyright (C) 2006, 2007, 2008, 2009, 2010, 2011, 2012 Apple Inc. All rights reserved.
  *
  * Portions are Copyright (C) 1998 Netscape Communications Corporation.
  *
  * Other contributors:
  *   Robert O'Callahan <roc+@cs.cmu.edu>
  *   David Baron <dbaron@fas.harvard.edu>
  *   Christian Biesinger <cbiesinger@web.de>
  *   Randall Jesup <rjesup@wgate.com>
@@ skipping 114 matching lines @@
     , m_hasUnclippedDescendant(false)
     , m_isUnclippedDescendant(false)
     , m_needsCompositedScrolling(false)
     , m_needsCompositedScrollingHasBeenRecorded(false)
     , m_willUseCompositedScrollingHasBeenRecorded(false)
     , m_isScrollableAreaHasBeenRecorded(false)
     , m_canBePromotedToStackingContainer(false)
     , m_canBePromotedToStackingContainerDirty(true)
     , m_isRootLayer(renderer->isRenderView())
     , m_usedTransparency(false)
+    , m_childLayerHasBlendMode(false)
+    , m_childLayerHasBlendModeStatusDirty(false)
     , m_paintingInsideReflection(false)
     , m_repaintStatus(NeedsNormalRepaint)
     , m_visibleContentStatusDirty(true)
     , m_hasVisibleContent(false)
     , m_visibleDescendantStatusDirty(false)
     , m_hasVisibleDescendant(false)
     , m_isPaginated(false)
     , m_3DTransformedDescendantStatusDirty(true)
     , m_has3DTransformedDescendant(false)
     , m_containsDirtyOverlayScrollbars(false)
@@ skipping 671 matching lines @@
 bool RenderLayer::hasBlendMode() const
 {
     return RuntimeEnabledFeatures::cssCompositingEnabled() && renderer()->hasBlendMode();
 }
 
 void RenderLayer::updateBlendMode()
 {
     if (!RuntimeEnabledFeatures::cssCompositingEnabled())
         return;
 
+    bool hadBlendMode = m_blendMode != BlendModeNormal;
     BlendMode newBlendMode = renderer()->style()->blendMode();
     if (newBlendMode != m_blendMode) {
         m_blendMode = newBlendMode;
+
+        // Only update the flag if a blend mode is set or unset.
+        if (!hadBlendMode || !hasBlendMode())
+            dirtyAncestorChainBlendedDescendantStatus();
+
         if (backing())
             backing()->setBlendMode(newBlendMode);
     }
 }
 
 void RenderLayer::updateTransform()
 {
     // hasTransform() on the renderer is also true when there is transform-style: preserve-3d or perspective set,
     // so check style too.
     bool hasTransform = renderer()->hasTransform() && renderer()->style()->hasTransform();
@@ skipping 212 matching lines @@
 {
     for (RenderLayer* layer = this; layer; layer = layer->parent()) {
         if (!layer->m_visibleDescendantStatusDirty && layer->hasVisibleDescendant())
             break;
 
         layer->m_hasVisibleDescendant = true;
         layer->m_visibleDescendantStatusDirty = false;
     }
 }
 
+void RenderLayer::dirtyAncestorChainBlendedDescendantStatus()
+{
+    for (RenderLayer* layer = this; layer; layer = layer->parent()) {
+        if (layer->m_childLayerHasBlendModeStatusDirty)
+            break;
+
+        layer->m_childLayerHasBlendModeStatusDirty = true;
+
+        if (layer->isStackingContext())
+            break;
+    }
+}
+
+void RenderLayer::setAncestorChainBlendedDescendant()
+{
+    for (RenderLayer* layer = this; layer; layer = layer->parent()) {
+        if (!layer->m_childLayerHasBlendModeStatusDirty && layer->childLayerHasBlendMode())
+            break;
+
+        layer->m_childLayerHasBlendMode = true;
+        layer->m_childLayerHasBlendModeStatusDirty = false;
+
+        if (layer->isStackingContext())
+            break;
+    }
+}
+
 void RenderLayer::updateHasUnclippedDescendant()
 {
     TRACE_EVENT0("blink_rendering", "RenderLayer::updateHasUnclippedDescendant");
     ASSERT(renderer()->isOutOfFlowPositioned());
     if (!m_hasVisibleContent && !m_hasVisibleDescendant)
         return;
 
     FrameView* frameView = renderer()->view()->frameView();
     if (!frameView)
         return;
@@ skipping 39 matching lines @@
 
             if (m_hasVisibleDescendant && m_hasSelfPaintingLayerDescendant && hasOutOfFlowPositionedDescendant)
                 break;
         }
 
         m_visibleDescendantStatusDirty = false;
         m_hasSelfPaintingLayerDescendantDirty = false;
         m_hasOutOfFlowPositionedDescendantDirty = false;
     }
 
+    if (m_childLayerHasBlendModeStatusDirty) {
+        for (RenderLayer* child = firstChild(); child; child = child->nextSibling()) {
+            child->updateDescendantDependentFlags();
+            if (child->hasBlendMode() || child->isStackingContext())
+                break;
+
+            bool childLayerHasBlendMode = child->hasBlendMode() || child->m_childLayerHasBlendMode;
+            m_childLayerHasBlendMode |= childLayerHasBlendMode;

[Julien - ping for review, 2013/10/03 21:38:28]

Normally we bail out if m_childLayerHasBlendMode but considering it's a rare
property, it probably wouldn't buy us much.

[mitica, 2013/10/07 10:56:03]

Good point, I've modified this function to break after reaching the first
blended child.

+        }
+        m_childLayerHasBlendModeStatusDirty = false;
+    }
+
     if (m_visibleContentStatusDirty) {
         if (renderer()->style()->visibility() == VISIBLE)
             m_hasVisibleContent = true;
         else {
             // layer may be hidden but still have some visible content, check for this
             m_hasVisibleContent = false;
             RenderObject* r = renderer()->firstChild();
             while (r) {
                 if (r->style()->visibility() == VISIBLE && !r->hasLayer()) {
                     m_hasVisibleContent = true;
@@ skipping 555 matching lines @@
     return clipRect;
 }
 
 LayoutRect RenderLayer::paintingExtent(const RenderLayer* rootLayer, const LayoutRect& paintDirtyRect, PaintBehavior paintBehavior)
 {
     return intersection(transparencyClipBox(this, rootLayer, PaintingTransparencyClipBox, RootOfTransparencyClipBox, paintBehavior), paintDirtyRect);
 }
 
 void RenderLayer::beginTransparencyLayers(GraphicsContext* context, const RenderLayer* rootLayer, const LayoutRect& paintDirtyRect, PaintBehavior paintBehavior)
 {
-    if (context->paintingDisabled() || (paintsWithTransparency(paintBehavior) && m_usedTransparency))
+    bool createTransparencyLayerForBlendMode = isStackingContext() && m_childLayerHasBlendMode;
+    if (context->paintingDisabled() || ((paintsWithTransparency(paintBehavior) || hasBlendMode() || createTransparencyLayerForBlendMode) && m_usedTransparency))
         return;
 
     RenderLayer* ancestor = transparentPaintingAncestor();
     if (ancestor)
         ancestor->beginTransparencyLayers(context, rootLayer, paintDirtyRect, paintBehavior);
 
-    if (paintsWithTransparency(paintBehavior)) {
+    if (paintsWithTransparency(paintBehavior) || hasBlendMode() || createTransparencyLayerForBlendMode) {
         m_usedTransparency = true;
         context->save();
         LayoutRect clipRect = paintingExtent(rootLayer, paintDirtyRect, paintBehavior);
         context->clip(clipRect);
+        if (hasBlendMode())
+            context->setCompositeOperation(context->compositeOperation(), m_blendMode);
+
         context->beginTransparencyLayer(renderer()->opacity());
 #ifdef REVEAL_TRANSPARENCY_LAYERS
         context->setFillColor(Color(0.0f, 0.0f, 0.5f, 0.2f));
         context->fillRect(clipRect);
 #endif
     }
 }
 
 void* RenderLayer::operator new(size_t sz)
 {
@@ skipping 34 matching lines @@
         child->dirtyStackingContainerZOrderLists();
     }
 
     child->updateDescendantDependentFlags();
     if (child->m_hasVisibleContent || child->m_hasVisibleDescendant)
         setAncestorChainHasVisibleDescendant();
 
     if (child->isSelfPaintingLayer() || child->hasSelfPaintingLayerDescendant())
         setAncestorChainHasSelfPaintingLayerDescendant();
 
+    if (child->hasBlendMode() || child->childLayerHasBlendMode())
+        setAncestorChainBlendedDescendant();
+
     if (subtreeContainsOutOfFlowPositionedLayer(child)) {
         // Now that the out of flow positioned descendant is in the tree, we
         // need to tell the compositor to reevaluate the compositing
         // requirements since we may be able to mark more layers as having
         // an 'unclipped' descendant.
         compositor()->setNeedsUpdateCompositingRequirementsState();
         setAncestorChainHasOutOfFlowPositionedDescendant();
     }
 
     // When we first dirty a layer, we will also dirty all the siblings in that
@@ skipping 41 matching lines @@
         compositor()->setNeedsUpdateCompositingRequirementsState();
         dirtyAncestorChainHasOutOfFlowPositionedDescendantStatus();
     }
 
     if (oldChild->m_hasVisibleContent || oldChild->m_hasVisibleDescendant)
         dirtyAncestorChainVisibleDescendantStatus();
 
     if (oldChild->isSelfPaintingLayer() || oldChild->hasSelfPaintingLayerDescendant())
         dirtyAncestorChainHasSelfPaintingLayerDescendantStatus();
 
+    if (oldChild->hasBlendMode() || oldChild->childLayerHasBlendMode())
+        dirtyAncestorChainBlendedDescendantStatus();
+
     return oldChild;
 }
 
 void RenderLayer::removeOnlyThisLayer()
 {
     if (!m_parent)
         return;
 
     // Mark that we are about to lose our layer. This makes render tree
     // walks ignore this layer while we're removing it.
@@ skipping 1379 matching lines @@
 
                 resourceClipper = toRenderSVGResourceClipper(element->renderer()->toRenderSVGResourceContainer());
                 if (!resourceClipper->applyClippingToContext(renderer(), rootRelativeBounds, paintingInfo.paintDirtyRect, context)) {
                     // No need to post-apply the clipper if this failed.
                     resourceClipper = 0;
                 }
             }
         }
     }
 
+    // Blending operations must be performed only with the nearest ancestor stacking context.
+    bool createTransparencyLayerForBlendMode = isStackingContext() && m_childLayerHasBlendMode;
+
+    if (createTransparencyLayerForBlendMode)
+        beginTransparencyLayers(context, paintingInfo.rootLayer, paintingInfo.paintDirtyRect, paintingInfo.paintBehavior);
+
     LayerPaintingInfo localPaintingInfo(paintingInfo);
     FilterEffectRendererHelper filterPainter(filterRenderer() && paintsWithFilters());
     if (filterPainter.haveFilterEffect() && !context->paintingDisabled()) {
         RenderLayerFilterInfo* filterInfo = this->filterInfo();
         ASSERT(filterInfo);
         LayoutRect filterRepaintRect = filterInfo->dirtySourceRect();
         filterRepaintRect.move(offsetFromRoot.x(), offsetFromRoot.y());
 
         if (!rootRelativeBoundsComputed) {
             rootRelativeBounds = calculateLayerBounds(paintingInfo.rootLayer, &offsetFromRoot, 0);
@@ skipping 101 matching lines @@
 
     if (shouldPaintMask)
         paintMaskForFragments(layerFragments, context, localPaintingInfo, paintingRootForRenderer);
 
     if (shouldPaintClippingMask) {
         // Paint the border radius mask for the fragments.
         paintChildClippingMaskForFragments(layerFragments, context, localPaintingInfo, paintingRootForRenderer);
     }
 
     // End our transparency layer
-    if (haveTransparency && m_usedTransparency && !m_paintingInsideReflection) {
+    if ((haveTransparency || hasBlendMode() || createTransparencyLayerForBlendMode) && m_usedTransparency && !m_paintingInsideReflection) {
         context->endLayer();
         context->restore();
         m_usedTransparency = false;
     }
 
     if (resourceClipper)
         resourceClipper->postApplyResource(renderer(), context, ApplyToDefaultMode, 0, 0);
 
     if (hasClipPath)
         context->restore();
@@ skipping 164 matching lines @@
 void RenderLayer::paintBackgroundForFragments(const LayerFragments& layerFragments, GraphicsContext* context, GraphicsContext* transparencyLayerContext,
     const LayoutRect& transparencyPaintDirtyRect, bool haveTransparency, const LayerPaintingInfo& localPaintingInfo, PaintBehavior paintBehavior,
     RenderObject* paintingRootForRenderer)
 {
     for (size_t i = 0; i < layerFragments.size(); ++i) {
         const LayerFragment& fragment = layerFragments.at(i);
         if (!fragment.shouldPaintContent)
             continue;
 
         // Begin transparency layers lazily now that we know we have to paint something.
-        if (haveTransparency)
+        if (haveTransparency || hasBlendMode())
             beginTransparencyLayers(transparencyLayerContext, localPaintingInfo.rootLayer, transparencyPaintDirtyRect, localPaintingInfo.paintBehavior);
 
         if (localPaintingInfo.clipToDirtyRect) {
             // Paint our background first, before painting any child layers.
             // Establish the clip used to paint our background.
             clipToRect(localPaintingInfo.rootLayer, context, localPaintingInfo.paintDirtyRect, fragment.backgroundRect, DoNotIncludeSelfForBorderRadius); // Background painting will handle clipping to self.
         }
 
         // Paint the background.
         // FIXME: Eventually we will collect the region from the fragment itself instead of just from the paint info.
         PaintInfo paintInfo(context, pixelSnappedIntRect(fragment.backgroundRect.rect()), PaintPhaseBlockBackground, paintBehavior, paintingRootForRenderer, localPaintingInfo.region, 0, 0, localPaintingInfo.rootLayer->renderer());
         renderer()->paint(paintInfo, toPoint(fragment.layerBounds.location() - renderBoxLocation() + localPaintingInfo.subPixelAccumulation));
 
         if (localPaintingInfo.clipToDirtyRect)
             restoreClip(context, localPaintingInfo.paintDirtyRect, fragment.backgroundRect);
     }
 }
 
 void RenderLayer::paintForegroundForFragments(const LayerFragments& layerFragments, GraphicsContext* context, GraphicsContext* transparencyLayerContext,
     const LayoutRect& transparencyPaintDirtyRect, bool haveTransparency, const LayerPaintingInfo& localPaintingInfo, PaintBehavior paintBehavior,
     RenderObject* paintingRootForRenderer, bool selectionOnly, bool forceBlackText)
 {
     // Begin transparency if we have something to paint.
-    if (haveTransparency) {
+    if (haveTransparency || hasBlendMode()) {
         for (size_t i = 0; i < layerFragments.size(); ++i) {
             const LayerFragment& fragment = layerFragments.at(i);
             if (fragment.shouldPaintContent && !fragment.foregroundRect.isEmpty()) {
                 beginTransparencyLayers(transparencyLayerContext, localPaintingInfo.rootLayer, transparencyPaintDirtyRect, localPaintingInfo.paintBehavior);
                 break;
             }
         }
     }
 
     PaintBehavior localPaintBehavior = forceBlackText ? (PaintBehavior)PaintBehaviorForceBlackText : paintBehavior;
@@ skipping 2061 matching lines @@
         removeReflection();
     else if (hasReflection()) {
         if (!m_reflection)
             createReflection();
         UseCounter::count(&renderer()->document(), UseCounter::Reflection);
         updateReflectionStyle();
     }
 
     updateResizerStyle();
 
+    if (RuntimeEnabledFeatures::cssCompositingEnabled())
+        updateBlendMode();
+
     updateDescendantDependentFlags();
     updateTransform();
 
-    if (RuntimeEnabledFeatures::cssCompositingEnabled())
-        updateBlendMode();
-
     bool didPaintWithFilters = false;
 
     if (paintsWithFilters())
         didPaintWithFilters = true;
     updateFilters(oldStyle, renderer()->style());
 
     const RenderStyle* newStyle = renderer()->style();
     if (compositor()->updateLayerCompositingState(this)
         || needsCompositingLayersRebuiltForClip(oldStyle, newStyle)
         || needsCompositingLayersRebuiltForOverflow(oldStyle, newStyle)
@@ skipping 372 matching lines @@
     }
 }
 
 void showLayerTree(const WebCore::RenderObject* renderer)
 {
     if (!renderer)
         return;
     showLayerTree(renderer->enclosingLayer());
 }
 #endif