Wrap SVGImage for container during paint

third_party/WebKit/Source/core/paint/SVGImagePainter.cpp

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "config.h"
 #include "core/paint/SVGImagePainter.h"
 
 #include "core/layout/ImageQualityController.h"
 #include "core/layout/LayoutImageResource.h"
 #include "core/layout/svg/LayoutSVGImage.h"
@@ skipping 13 matching lines @@
 {
     if (paintInfo.phase != PaintPhaseForeground
         || m_layoutSVGImage.style()->visibility() == HIDDEN
         || !m_layoutSVGImage.imageResource()->hasImage())
         return;
 
     FloatRect boundingBox = m_layoutSVGImage.paintInvalidationRectInLocalCoordinates();
     if (!paintInfo.cullRect().intersectsCullRect(m_layoutSVGImage.localToParentTransform(), boundingBox))
         return;
 
+    FloatSize imageViewportSize = computeImageViewportSize();
+    if (imageViewportSize.isEmpty())
+        return;

[fs, 2015/11/16 15:08:07]

Won't this mean that we could miss out on some of the "effects" below?
('filter', 'outline', etc.) The area to draw into could still be non-empty.

[davve, 2015/11/16 16:32:40]

Moving the check to SVGImagePainter::paintForeground (where I had it the first 7
or so patch sets) seems reasonable. Testing the expanded (int)size seems to make
more sense too.

http://software.hixie.ch/utilities/js/live-dom-viewer/saved/3750

is one example where it actually makes a difference. I had to pull out
preserveAspectRatio='none' to trigger it. But that whole business in
computeImageViewport seems a bit fishy to me.

[fs, 2015/11/16 16:43:21]

Yes, computeImageViewport is fishy business (said one of the fishermen...)

+
     PaintInfo paintInfoBeforeFiltering(paintInfo);
     // Images cannot have children so do not call updateCullRect.
     TransformRecorder transformRecorder(*paintInfoBeforeFiltering.context, m_layoutSVGImage, m_layoutSVGImage.localToParentTransform());
     {
         SVGPaintContext paintContext(m_layoutSVGImage, paintInfoBeforeFiltering);
         if (paintContext.applyClipMaskAndFilterIfNecessary() && !LayoutObjectDrawingRecorder::useCachedDrawingIfPossible(*paintContext.paintInfo().context, m_layoutSVGImage, paintContext.paintInfo().phase, LayoutPoint())) {
             LayoutObjectDrawingRecorder recorder(*paintContext.paintInfo().context, m_layoutSVGImage, paintContext.paintInfo().phase, boundingBox, LayoutPoint());
-            paintForeground(paintContext.paintInfo());
+            paintForeground(paintContext.paintInfo(), imageViewportSize);
         }
     }
 
     if (m_layoutSVGImage.style()->outlineWidth()) {
         PaintInfo outlinePaintInfo(paintInfoBeforeFiltering);
         outlinePaintInfo.phase = PaintPhaseSelfOutline;
         ObjectPainter(m_layoutSVGImage).paintOutline(outlinePaintInfo, LayoutPoint(boundingBox.location()));
     }
 }
 
-void SVGImagePainter::paintForeground(const PaintInfo& paintInfo)
+void SVGImagePainter::paintForeground(const PaintInfo& paintInfo, const FloatSize& imageViewportSize)
 {
-    RefPtr<Image> image = m_layoutSVGImage.imageResource()->image(IntSize());
+    const LayoutImageResource* imageResource = m_layoutSVGImage.imageResource();
+
+    RefPtr<Image> image = imageResource->image(expandedIntSize(imageViewportSize), m_layoutSVGImage.style()->effectiveZoom());

[fs, 2015/11/16 15:08:07]

expandedIntSize used to be roundedIntSize I think, but expanding does seem
slightly more reasonable to me.

[davve, 2015/11/16 16:32:40]

Yes, I couldn't really make sense of that.

     FloatRect destRect = m_layoutSVGImage.objectBoundingBox();
     FloatRect srcRect(0, 0, image->width(), image->height());
 
     SVGImageElement* imageElement = toSVGImageElement(m_layoutSVGImage.element());
     imageElement->preserveAspectRatio()->currentValue()->transformRect(destRect, srcRect);
 
     InterpolationQuality interpolationQuality = InterpolationDefault;
     interpolationQuality = ImageQualityController::imageQualityController()->chooseInterpolationQuality(paintInfo.context, &m_layoutSVGImage, image.get(), image.get(), LayoutSize(destRect.size()));
 
     InterpolationQuality previousInterpolationQuality = paintInfo.context->imageInterpolationQuality();
     paintInfo.context->setImageInterpolationQuality(interpolationQuality);
     paintInfo.context->drawImage(image.get(), destRect, srcRect, SkXfermode::kSrcOver_Mode);
     paintInfo.context->setImageInterpolationQuality(previousInterpolationQuality);
 }
 
+FloatSize SVGImagePainter::computeImageViewportSize() const
+{
+    ASSERT(m_layoutSVGImage.imageResource()->hasImage());
+
+    if (toSVGImageElement(m_layoutSVGImage.element())->preserveAspectRatio()->currentValue()->align() != SVGPreserveAspectRatio::SVG_PRESERVEASPECTRATIO_NONE)
+        return m_layoutSVGImage.objectBoundingBox().size();
+
+    ImageResource* cachedImage = m_layoutSVGImage.imageResource()->cachedImage();
+
+    // Images with preserveAspectRatio=none should force non-uniform
+    // scaling. This can be achieved by setting the image's container size to
+    // its viewport size (i.e. if a viewBox is available - use that - else use intrinsic size.)
+    // See: http://www.w3.org/TR/SVG/single-page.html, 7.8 The 'preserveAspectRatio' attribute.
+    Length intrinsicWidth;
+    Length intrinsicHeight;
+    FloatSize intrinsicRatio;
+    cachedImage->computeIntrinsicDimensions(intrinsicWidth, intrinsicHeight, intrinsicRatio);
+    return intrinsicRatio;
+}
+
 } // namespace blink