[Slimming Paint] Implement deferred SVG filters

Source/core/rendering/svg/SVGRenderingContext.cpp

 /*
  * Copyright (C) 2007, 2008 Rob Buis <buis@kde.org>
  * Copyright (C) 2007 Nikolas Zimmermann <zimmermann@kde.org>
  * Copyright (C) 2007 Eric Seidel <eric@webkit.org>
  * Copyright (C) 2009 Google, Inc.  All rights reserved.
  * Copyright (C) 2009 Dirk Schulze <krit@webkit.org>
  * Copyright (C) Research In Motion Limited 2009-2010. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
@@ skipping 16 matching lines @@
 
 #include "core/frame/FrameHost.h"
 #include "core/rendering/PaintInfo.h"
 #include "core/rendering/RenderLayer.h"
 #include "core/rendering/svg/RenderSVGResourceFilter.h"
 #include "core/rendering/svg/RenderSVGResourceMasker.h"
 #include "core/rendering/svg/SVGRenderSupport.h"
 #include "core/rendering/svg/SVGResources.h"
 #include "core/rendering/svg/SVGResourcesCache.h"
 #include "platform/FloatConversion.h"
+#include "platform/graphics/paint/DrawingRecorder.h"
 
 namespace blink {
 
 SVGRenderingContext::~SVGRenderingContext()
 {
     if (m_filter) {
         ASSERT(SVGResourcesCache::cachedResourcesForRenderObject(m_object));
         ASSERT(SVGResourcesCache::cachedResourcesForRenderObject(m_object)->filter() == m_filter);
-        m_filter->finishEffect(m_object, m_paintInfo.context);
+
+        DrawingRecorder recorder(m_originalPaintInfo->context, m_object->displayItemClient(), DisplayItem::SVGFilter, LayoutRect::infiniteRect());
+        m_filter->finishEffect(m_object, m_originalPaintInfo->context);
+
+        // Reset the paint info after the filter effect has been completed.
+        m_paintInfo.context = m_originalPaintInfo->context;
+        m_paintInfo.rect = m_originalPaintInfo->rect;

[fs, 2015/01/26 09:47:11]

m_paintInfo.rect is "dead" at this point (not used below this point, and scopes
out at the end of this function.) Might be worth adding a note/assert/something
to that effect?

(With this line of reasoning I suppose m_originalPaintInfo->context could be
passed to the other two finishEffect()s as well... since m_paintInfo.context ===
m_originalPaintInfo->context after this point. A think a note will do fine
though at this point.)

[pdr., 2015/01/28 01:04:39]

Yeah, I thought it would be clean to fully clean up even though it isn't used
today (or, likely ever). I'll add a note.

     }
 
     if (m_masker) {
         ASSERT(SVGResourcesCache::cachedResourcesForRenderObject(m_object));
         ASSERT(SVGResourcesCache::cachedResourcesForRenderObject(m_object)->masker() == m_masker);
         m_masker->finishEffect(m_object, m_paintInfo.context);
     }
 
     if (m_clipper) {
         ASSERT(SVGResourcesCache::cachedResourcesForRenderObject(m_object));
@@ skipping 86 matching lines @@
     }
     return true;
 }
 
 bool SVGRenderingContext::applyFilterIfNecessary(SVGResources* resources)
 {
     if (!resources) {
         if (m_object->style()->svgStyle().hasFilter())
             return false;
     } else if (RenderSVGResourceFilter* filter = resources->filter()) {
-        if (!filter->prepareEffect(m_object, m_paintInfo.context))
+        GraphicsContext* filterContext = filter->prepareEffect(m_object, m_paintInfo.context);
+        if (!filterContext)
             return false;
         m_filter = filter;
 
+        // Because the filter needs to cache its contents we replace the context
+        // during filtering with the filter's context.
+        m_paintInfo.context = filterContext;
+
         // Because we cache the filter contents and do not invalidate on paint
         // invalidation rect changes, we need to paint the entire filter region
         // so elements outside the initial paint (due to scrolling, etc) paint.
         m_paintInfo.rect = LayoutRect::infiniteIntRect();
     }
     return true;
 }
 
 bool SVGRenderingContext::isIsolationInstalled() const
 {
@@ skipping 70 matching lines @@
 {
     ASSERT(context);
     ASSERT(item);
     ASSERT(!item->needsLayout());
 
     PaintInfo info(context, LayoutRect::infiniteIntRect(), PaintPhaseForeground, PaintBehaviorNormal);
     item->paint(info, IntPoint());
 }
 
 } // namespace blink