Rounded background image fast path

third_party/WebKit/Source/platform/graphics/GradientGeneratedImage.cpp

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 #include "platform/graphics/GradientGeneratedImage.h"
 
 #include "platform/geometry/FloatRect.h"
+#include "platform/geometry/IntSize.h"
 #include "platform/graphics/GraphicsContext.h"
 
 namespace blink {
 
 void GradientGeneratedImage::draw(SkCanvas* canvas, const SkPaint& paint, const FloatRect& destRect, const FloatRect& srcRect, RespectImageOrientationEnum, ImageClampingMode)
 {
     SkRect visibleRect = srcRect;
     if (!visibleRect.intersect(SkRect::MakeIWH(m_size.width(), m_size.height())))
         return;
 
     SkMatrix transform = SkMatrix::MakeRectToRect(srcRect, destRect, SkMatrix::kFill_ScaleToFit);
     SkAutoCanvasRestore autoRestore(canvas, !transform.isIdentity());
     canvas->concat(transform);
 
     SkPaint gradientPaint(paint);
     m_gradient->applyToPaint(gradientPaint);
 
     canvas->drawRect(visibleRect, gradientPaint);
 }
 
 void GradientGeneratedImage::drawTile(GraphicsContext& context, const FloatRect& srcRect)
 {
     context.setFillGradient(m_gradient);
     context.fillRect(srcRect);
 }
 
+bool GradientGeneratedImage::applyShader(SkPaint& paint, const SkMatrix* localMatrix)
+{
+    AffineTransform transform;
+    if (localMatrix) {
+        transform.setMatrix(
+            localMatrix->getScaleX(), localMatrix->getSkewY(),
+            localMatrix->getSkewX(), localMatrix->getScaleY(),
+            localMatrix->getTranslateX(), localMatrix->getTranslateY());
+    }
+
+    DCHECK(m_gradient);
+    m_gradient->setGradientSpaceTransform(transform);

[fs, 2016/05/20 12:47:35]

Could this end up affecting the result of a draw() if we have a sequence
"applyShader(...)", "draw()" on the same GradientGeneratedImage? I.e
state-pollution.

[f(malita), 2016/05/20 13:57:57]

Hmm, good question.  I thought we always update the gradient transform when
painting (SVG at least seems to do that), but yeah - the draw() path above
pushes the transform to the canvas, not to the gradient.  I guess for CSS
gradients we never touch the transform?

Updated to preserve the original gradient transform (always identity for
GradientGeneratedImage?).

(follow-up idea: I think in the long run it would be nicer to remove the
transform from the gradient/pattern state altogether and instead pass an
optional matrix to applyToPaint();  then the matrix is part of the key for the
cached shader, but no longer exposed/manipulated independently on the gradient
object)

[fs, 2016/05/20 14:18:56]

The transform is never touch explicitly (and this is where I usually go
"oh..."), but createShader does mutate the gradient-space-transform to achieve
elliptical gradients. (Should be easy to fix that oddity though...)
 
Yes, that'd be nice (I think we'd like that for SVG gradients too.)

+    m_gradient->applyToPaint(paint);
+
+    return true;
+}
+
 } // namespace blink