Fix display list canvas not rendering correctly on high dpi displays

Source/platform/graphics/GraphicsContext.cpp

 /*
  * Copyright (C) 2003, 2004, 2005, 2006, 2009 Apple Inc. All rights reserved.
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
@@ skipping 42 matching lines @@
 #include "third_party/skia/include/effects/SkCornerPathEffect.h"
 #include "third_party/skia/include/effects/SkDropShadowImageFilter.h"
 #include "third_party/skia/include/effects/SkLumaColorFilter.h"
 #include "third_party/skia/include/effects/SkMatrixImageFilter.h"
 #include "third_party/skia/include/effects/SkPictureImageFilter.h"
 #include "third_party/skia/include/gpu/GrRenderTarget.h"
 #include "third_party/skia/include/gpu/GrTexture.h"
 #include "wtf/Assertions.h"
 #include "wtf/MathExtras.h"
 
-namespace {
-
-// Tolerance value use for comparing scale factor to 1..
-// Numerical error should not reach 6th decimal except for highly degenerate cases,
-// and effect of 6th decimal on scale is negligible over max span of a skia canvas
-// which is 32k pixels.
-const float cPictureScaleEpsilon = 0.000001;
-
-}
-
 namespace blink {
 
 class GraphicsContext::RecordingState {
     WTF_MAKE_FAST_ALLOCATED;
     WTF_MAKE_NONCOPYABLE(RecordingState);
 public:
     static PassOwnPtr<RecordingState> Create(SkCanvas* canvas, const SkMatrix& matrix, unsigned trackingMode)
     {
         return adoptPtr(new RecordingState(canvas, matrix, static_cast<RegionTrackingMode>(trackingMode)));
     }
@@ skipping 488 matching lines @@
 
     if (regionTrackingEnabled()) {
         // Since we don't track regions within display lists, conservatively
         // mark the bounds as non-opaque.
         SkPaint paint;
         paint.setXfermodeMode(SkXfermode::kClear_Mode);
         m_trackedRegion.didDrawBounded(this, picture->cullRect(), paint);
     }
 }
 
-static inline bool pictureScaleIsApproximatelyOne(float x)
-{
-    return fabsf(x - 1.0f) < cPictureScaleEpsilon;
-}
-
-void GraphicsContext::drawPicture(SkPicture* picture, const FloatRect& dest, const FloatRect& src, CompositeOperator op, WebBlendMode blendMode)
+void GraphicsContext::compositePicture(SkPicture* picture, const FloatRect& dest, const FloatRect& src, CompositeOperator op, WebBlendMode blendMode)

[Stephen White, 2014/12/12 22:14:11]

Why the name change? Most draw ops in GraphicsContext are called drawFoo(), even
if they also perform compositing.

[Justin Novosad, 2014/12/12 22:31:51]

Because the behavior is significantly different from the drawPicture just above,
which draw directly into the graphic context. This method, on the other hand,
draws into an intermediate buffer, so the picture gets composited as a whole (as
opposed to one primitive at a time).

 {
     ASSERT(m_canvas);
     if (contextDisabled() || !picture)
         return;
 
-    SkMatrix ctm = m_canvas->getTotalMatrix();
-    SkRect deviceDest;
-    ctm.mapRect(&deviceDest, dest);
-    float scaleX = deviceDest.width() / src.width();
-    float scaleY = deviceDest.height() / src.height();
-
     SkPaint picturePaint;
     picturePaint.setXfermodeMode(WebCoreCompositeToSkiaComposite(op, blendMode));
+    m_canvas->save();
     SkRect sourceBounds = WebCoreFloatRectToSKRect(src);
-    if (pictureScaleIsApproximatelyOne(scaleX * m_deviceScaleFactor) && pictureScaleIsApproximatelyOne(scaleY * m_deviceScaleFactor)) {
-        // Fast path for canvases that are rasterized at screen resolution
-        SkRect skBounds = WebCoreFloatRectToSKRect(dest);
-        m_canvas->saveLayer(&skBounds, &picturePaint);
-        SkMatrix pictureTransform;
-        pictureTransform.setRectToRect(sourceBounds, skBounds, SkMatrix::kFill_ScaleToFit);
-        m_canvas->concat(pictureTransform);
-        m_canvas->drawPicture(picture);
-        m_canvas->restore();
-    } else {
-        RefPtr<SkPictureImageFilter> pictureFilter = adoptRef(SkPictureImageFilter::Create(picture, sourceBounds));
-        SkMatrix layerScale;
-        layerScale.setScale(scaleX, scaleY);
-        RefPtr<SkMatrixImageFilter> matrixFilter = adoptRef(SkMatrixImageFilter::Create(layerScale, SkPaint::kLow_FilterLevel, pictureFilter.get()));
-        picturePaint.setImageFilter(matrixFilter.get());
-        SkRect layerBounds = SkRect::MakeWH(std::max(deviceDest.width(), sourceBounds.width()), std::max(deviceDest.height(), sourceBounds.height()));
-        m_canvas->save();
-        m_canvas->resetMatrix();
-        m_canvas->translate(deviceDest.x(), deviceDest.y());
-        m_canvas->saveLayer(&layerBounds, &picturePaint);
-        m_canvas->restore();
-        m_canvas->restore();
-    }
+    SkRect skBounds = WebCoreFloatRectToSKRect(dest);
+    SkMatrix pictureTransform;
+    pictureTransform.setRectToRect(sourceBounds, skBounds, SkMatrix::kFill_ScaleToFit);
+    m_canvas->concat(pictureTransform);
+    RefPtr<SkPictureImageFilter> pictureFilter = adoptRef(SkPictureImageFilter::CreateForLocalSpace(picture, sourceBounds, static_cast<SkPaint::FilterLevel>(imageInterpolationQuality())));
+    picturePaint.setImageFilter(pictureFilter.get());
+    m_canvas->saveLayer(&sourceBounds, &picturePaint);
+    m_canvas->restore();
+    m_canvas->restore();
 }
 
 void GraphicsContext::fillPolygon(size_t numPoints, const FloatPoint* points, const Color& color,
     bool shouldAntialias)
 {
     if (contextDisabled())
         return;
 
     ASSERT(numPoints > 2);
 
@@ skipping 1354 matching lines @@
 GraphicsContext::AutoCanvasRestorer::~AutoCanvasRestorer()
 {
     while (m_restoreCount) {
         m_canvas->restore();
         m_restoreCount--;
     }
 
 }
 
 } // namespace blink