Draw thin slices of an image w/ anti-aliasing for 2D <canvas>

Source/platform/graphics/GraphicsContext.h

Index: Source/platform/graphics/GraphicsContext.h
diff --git a/Source/platform/graphics/GraphicsContext.h b/Source/platform/graphics/GraphicsContext.h
index add6d3c26e59a1e6324dce9fc15eb4094038e3fd..7c60ce6f1b25231fa5bbd321ff440209769d051a 100644
--- a/Source/platform/graphics/GraphicsContext.h
+++ b/Source/platform/graphics/GraphicsContext.h
@@ -136,6 +136,12 @@ public:
     void setShouldAntialias(bool antialias) { mutableState()->setShouldAntialias(antialias); }
     bool shouldAntialias() const { return immutableState()->shouldAntialias(); }
 
+    // Enables the use of the shouldAntialias flag for images. Note that this
+    // only affects the (rasterized) image geometry, and not the quality of the
+    // interpolation (for that, see setImageInterpolationQuality.)
+    void enableDefaultAntialiasingForImages() { m_antialiasImages = true; }
+    bool shouldAntialiasImages() const { return m_antialiasImages && shouldAntialias(); }

[Justin Novosad, 2014/03/28 18:20:38]

I think the name is a bit misleading. Perhaps: shouldAntialiasHairline Images?
or thin images? something like that.  The fact is that rotated/skewed images
will still be draw anti-aliased even if this bit is not set.

[fs, 2014/03/31 08:21:11]

Makes sense. Renamed accordingly.

It also occurred to me that it might make sense to reverse the logic (and hence
settings) to always enable AA, but then selectively disable it for the
rectilinear cases (except the "hairline" case, which would then still have a
flag I suppose - so no major improvement in cleanliness.) If that sounds
reasonable, I'd be happy to do that change here or as a follow up CL.

+
     void setShouldClampToSourceRect(bool clampToSourceRect) { mutableState()->setShouldClampToSourceRect(clampToSourceRect); }
     bool shouldClampToSourceRect() const { return immutableState()->shouldClampToSourceRect(); }
 
@@ -504,6 +510,7 @@ private:
     bool m_accelerated : 1;
     bool m_isCertainlyOpaque : 1;
     bool m_printing : 1;
+    bool m_antialiasImages : 1;
 };
 
 } // namespace WebCore