[SVG] DisplayList-based patterns.

Source/core/rendering/svg/RenderSVGResourcePattern.cpp

Index: Source/core/rendering/svg/RenderSVGResourcePattern.cpp
diff --git a/Source/core/rendering/svg/RenderSVGResourcePattern.cpp b/Source/core/rendering/svg/RenderSVGResourcePattern.cpp
index a15d4f3813c225a06ade3659b7b2e4fbc96cb201..71d08069dc058d8505b0809293e356a20d0b53e2 100644
--- a/Source/core/rendering/svg/RenderSVGResourcePattern.cpp
+++ b/Source/core/rendering/svg/RenderSVGResourcePattern.cpp
@@ -1,6 +1,7 @@
 /*
  * Copyright (C) 2006 Nikolas Zimmermann <zimmermann@kde.org>
  * Copyright (C) Research In Motion Limited 2010. All rights reserved.
+ * Copyright 2014 The Chromium Authors. 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
@@ -24,10 +25,19 @@
 #include "core/dom/ElementTraversal.h"
 #include "core/rendering/svg/SVGRenderingContext.h"
 #include "core/svg/SVGFitToViewBox.h"
+#include "core/svg/SVGPatternElement.h"
+#include "platform/graphics/DisplayList.h"
 #include "platform/graphics/GraphicsContext.h"
 
 namespace blink {
 
+struct PatternData {
+    WTF_MAKE_FAST_ALLOCATED;
+public:
+    RefPtr<Pattern> pattern;
+    AffineTransform transform;
+};
+
 const RenderSVGResourceType RenderSVGResourcePattern::s_resourceType = PatternResourceType;
 
 RenderSVGResourcePattern::RenderSVGResourcePattern(SVGPatternElement* node)
@@ -50,63 +60,57 @@ void RenderSVGResourcePattern::removeClientFromCache(RenderObject* client, bool
     markClientForInvalidation(client, markForInvalidation ? PaintInvalidation : ParentOnlyInvalidation);
 }
 
-PatternData* RenderSVGResourcePattern::buildPattern(const RenderObject& object, const SVGPatternElement* patternElement)
+PatternData* RenderSVGResourcePattern::patternForRenderer(const RenderObject& object)
 {
-    PatternData* currentData = m_patternMap.get(&object);
-    if (currentData && currentData->pattern)
-        return currentData;
+    OwnPtr<PatternData>& patternData = m_patternMap.add(&object, nullptr).storedValue->value;

[Stephen White, 2014/10/22 15:11:26]

Nit: This seems a bit of a convoluted way to use a map.

Couldn't we use HashMap::find() to get an iterator, and if found, do an
early-return? Then you would only need to add() in the not-found case.

[f(malita), 2014/10/22 16:23:47]

I agree it's convoluted, but it avoids a double hash lookup in the not-found
case. The idiom is quite common (we use it in RenderSVGResourceGradient and a
bunch of other places if you grep around for "add.*, nullptr"), but maybe I can
make it more clear with an AddResult like the other users.

Done.

[Stephen White, 2014/10/22 17:50:48]

Acknowledged.

+    if (!patternData)
+        patternData = buildPatternData(object);
+
+    ASSERT(!m_shouldCollectPatternAttributes);
+    return patternData.get();
+}
 
+PassOwnPtr<PatternData> RenderSVGResourcePattern::buildPatternData(const RenderObject& object)
+{
     // If we couldn't determine the pattern content element root, stop here.
     if (!m_attributes.patternContentElement())
-        return 0;
+        return nullptr;
 
     // An empty viewBox disables rendering.
     if (m_attributes.hasViewBox() && m_attributes.viewBox().isEmpty())
-        return 0;
-
-    // Compute all necessary transformations to build the tile image & the pattern.
-    FloatRect tileBoundaries;
-    AffineTransform tileImageTransform;
-    if (!buildTileImageTransform(object, m_attributes, patternElement, tileBoundaries, tileImageTransform))
-        return 0;
-
-    AffineTransform absoluteTransformIgnoringRotation;
-    SVGRenderingContext::calculateDeviceSpaceTransformation(&object, absoluteTransformIgnoringRotation);
-
-    // Ignore 2D rotation, as it doesn't affect the size of the tile.
-    SVGRenderingContext::clear2DRotation(absoluteTransformIgnoringRotation);
-    FloatRect absoluteTileBoundaries = absoluteTransformIgnoringRotation.mapRect(tileBoundaries);
-
-    // Scale the tile size to match the scale level of the patternTransform.
-    absoluteTileBoundaries.scale(static_cast<float>(m_attributes.patternTransform().xScale()),
-        static_cast<float>(m_attributes.patternTransform().yScale()));
+        return nullptr;
 
-    // Build tile image.
-    OwnPtr<ImageBuffer> tileImage = createTileImage(m_attributes, tileBoundaries, absoluteTileBoundaries, tileImageTransform);
-    if (!tileImage)
-        return 0;
+    ASSERT(element());
+    // Compute tile metrics.
+    FloatRect clientBoundingBox = object.objectBoundingBox();
+    FloatRect tileBounds = SVGLengthContext::resolveRectangle(element(),
+        m_attributes.patternUnits(), clientBoundingBox,
+        m_attributes.x(), m_attributes.y(), m_attributes.width(), m_attributes.height());
+    if (tileBounds.isEmpty())
+        return nullptr;
 
-    RefPtr<Image> copiedImage = tileImage->copyImage(CopyBackingStore);
-    if (!copiedImage)
-        return 0;
+    AffineTransform tileTransform;
+    if (m_attributes.hasViewBox()) {
+        if (m_attributes.viewBox().isEmpty())
+            return nullptr;
+        tileTransform = SVGFitToViewBox::viewBoxToViewTransform(m_attributes.viewBox(),
+            m_attributes.preserveAspectRatio(), tileBounds.width(), tileBounds.height());
+    } else {
+        // A viewbox overrides patternContentUnits, per spec.
+        if (m_attributes.patternContentUnits() == SVGUnitTypes::SVG_UNIT_TYPE_OBJECTBOUNDINGBOX)
+            tileTransform.scale(clientBoundingBox.width(), clientBoundingBox.height());
+    }
 
-    // Build pattern.
     OwnPtr<PatternData> patternData = adoptPtr(new PatternData);
-    patternData->pattern = Pattern::createBitmapPattern(copiedImage);
+    patternData->pattern = Pattern::createDisplayListPattern(asDisplayList(tileBounds, tileTransform));
 
     // Compute pattern space transformation.
-    const IntSize tileImageSize = tileImage->size();
-    patternData->transform.translate(tileBoundaries.x(), tileBoundaries.y());
-    patternData->transform.scale(tileBoundaries.width() / tileImageSize.width(), tileBoundaries.height() / tileImageSize.height());
-
+    patternData->transform.translate(tileBounds.x(), tileBounds.y());
     AffineTransform patternTransform = m_attributes.patternTransform();
     if (!patternTransform.isIdentity())
         patternData->transform = patternTransform * patternData->transform;
 
-    // Various calls above may trigger invalidations in some fringe cases (ImageBuffer allocation
-    // failures in the SVG image cache for example). To avoid having our PatternData deleted by
-    // removeAllClientsFromCache(), we only make it visible in the cache at the very end.
-    return m_patternMap.set(&object, patternData.release()).storedValue->value.get();
+    return patternData.release();
 }
 
 SVGPaintServer RenderSVGResourcePattern::preparePaintServer(const RenderObject& object)
@@ -131,7 +135,7 @@ SVGPaintServer RenderSVGResourcePattern::preparePaintServer(const RenderObject&
     if (m_attributes.patternUnits() == SVGUnitTypes::SVG_UNIT_TYPE_OBJECTBOUNDINGBOX && objectBoundingBox.isEmpty())
         return SVGPaintServer::invalid();
 
-    PatternData* patternData = buildPattern(object, patternElement);
+    PatternData* patternData = patternForRenderer(object);
     if (!patternData)
         return SVGPaintServer::invalid();
 
@@ -140,80 +144,30 @@ SVGPaintServer RenderSVGResourcePattern::preparePaintServer(const RenderObject&
     return SVGPaintServer(patternData->pattern);
 }
 
-static inline FloatRect calculatePatternBoundaries(const PatternAttributes& attributes,
-                                                   const FloatRect& objectBoundingBox,
-                                                   const SVGPatternElement* patternElement)
-{
-    ASSERT(patternElement);
-    return SVGLengthContext::resolveRectangle(patternElement, attributes.patternUnits(), objectBoundingBox, attributes.x(), attributes.y(), attributes.width(), attributes.height());
-}
-
-bool RenderSVGResourcePattern::buildTileImageTransform(const RenderObject& renderer,
-                                                       const PatternAttributes& attributes,
-                                                       const SVGPatternElement* patternElement,
-                                                       FloatRect& patternBoundaries,
-                                                       AffineTransform& tileImageTransform) const
+PassRefPtr<DisplayList> RenderSVGResourcePattern::asDisplayList(const FloatRect& tileBounds,
+    const AffineTransform& tileTransform) const
 {
-    ASSERT(patternElement);
+    ASSERT(!m_shouldCollectPatternAttributes);
 
-    FloatRect objectBoundingBox = renderer.objectBoundingBox();
-    patternBoundaries = calculatePatternBoundaries(attributes, objectBoundingBox, patternElement);
-    if (patternBoundaries.width() <= 0 || patternBoundaries.height() <= 0)
-        return false;
+    AffineTransform contentTransform;
+    if (m_attributes.patternContentUnits() == SVGUnitTypes::SVG_UNIT_TYPE_OBJECTBOUNDINGBOX)
+        contentTransform = tileTransform;
 
-    AffineTransform viewBoxCTM = SVGFitToViewBox::viewBoxToViewTransform(attributes.viewBox(), attributes.preserveAspectRatio(), patternBoundaries.width(), patternBoundaries.height());
+    // Draw the content into a DisplayList.
+    GraphicsContext recordingContext(nullptr);
+    recordingContext.beginRecording(FloatRect(FloatPoint(), tileBounds.size()));
+    recordingContext.concatCTM(tileTransform);
 
-    // Apply viewBox/objectBoundingBox transformations.
-    if (!viewBoxCTM.isIdentity())
-        tileImageTransform = viewBoxCTM;
-    else if (attributes.patternContentUnits() == SVGUnitTypes::SVG_UNIT_TYPE_OBJECTBOUNDINGBOX)
-        tileImageTransform.scale(objectBoundingBox.width(), objectBoundingBox.height());
+    ASSERT(m_attributes.patternContentElement());
+    RenderSVGResourceContainer* patternRenderer =
+        toRenderSVGResourceContainer(m_attributes.patternContentElement()->renderer());
+    ASSERT(patternRenderer);
+    ASSERT(!patternRenderer->needsLayout());
 
-    return true;
-}
-
-PassOwnPtr<ImageBuffer> RenderSVGResourcePattern::createTileImage(const PatternAttributes& attributes,
-                                                                  const FloatRect& tileBoundaries,
-                                                                  const FloatRect& absoluteTileBoundaries,
-                                                                  const AffineTransform& tileImageTransform) const
-{
-    FloatRect clampedAbsoluteTileBoundaries = SVGRenderingContext::clampedAbsoluteTargetRect(absoluteTileBoundaries);
-
-    IntSize imageSize(roundedIntSize(clampedAbsoluteTileBoundaries.size()));
-    if (imageSize.isEmpty())
-        return nullptr;
-    OwnPtr<ImageBuffer> tileImage = ImageBuffer::create(imageSize);
-    if (!tileImage)
-        return nullptr;
-
-    GraphicsContext* tileImageContext = tileImage->context();
-    ASSERT(tileImageContext);
-    IntSize unclampedImageSize(roundedIntSize(absoluteTileBoundaries.size()));
-    tileImageContext->scale(unclampedImageSize.width() / absoluteTileBoundaries.width(), unclampedImageSize.height() / absoluteTileBoundaries.height());
-
-    // The image buffer represents the final rendered size, so the content has to be scaled (to avoid pixelation).
-    tileImageContext->scale(
-        clampedAbsoluteTileBoundaries.width() / tileBoundaries.width(),
-        clampedAbsoluteTileBoundaries.height() / tileBoundaries.height());
-
-    // Apply tile image transformations.
-    if (!tileImageTransform.isIdentity())
-        tileImageContext->concatCTM(tileImageTransform);
-
-    AffineTransform contentTransformation;
-    if (attributes.patternContentUnits() == SVGUnitTypes::SVG_UNIT_TYPE_OBJECTBOUNDINGBOX)
-        contentTransformation = tileImageTransform;
-
-    // Draw the content into the ImageBuffer.
-    for (SVGElement* element = Traversal<SVGElement>::firstChild(*attributes.patternContentElement()); element; element = Traversal<SVGElement>::nextSibling(*element)) {
-        if (!element->renderer())
-            continue;
-        if (element->renderer()->needsLayout())
-            return nullptr;
-        SVGRenderingContext::renderSubtree(tileImage->context(), element->renderer(), contentTransformation);
-    }
+    for (RenderObject* child = patternRenderer->firstChild(); child; child = child->nextSibling())
+        SVGRenderingContext::renderSubtree(&recordingContext, child, contentTransform);
 
-    return tileImage.release();
+    return recordingContext.endRecording();
 }
 
 }