Move blend optimization functions to GrDrawState.
Review URL: https://codereview.appspot.com/7300089
git-svn-id: http://skia.googlecode.com/svn/trunk@7703 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/src/gpu/GrDrawState.h b/src/gpu/GrDrawState.h
index 2245e05..1124ebb 100644
--- a/src/gpu/GrDrawState.h
+++ b/src/gpu/GrDrawState.h
@@ -690,6 +690,60 @@
*/
GrColor getBlendConstant() const { return fCommon.fBlendConstant; }
+ /**
+ * Determines whether multiplying the computed per-pixel color by the pixel's fractional
+ * coverage before the blend will give the correct final destination color. In general it
+ * will not as coverage is applied after blending.
+ */
+ bool canTweakAlphaForCoverage() const;
+
+ /**
+ * Optimizations for blending / coverage to that can be applied based on the current state.
+ */
+ enum BlendOptFlags {
+ /**
+ * No optimization
+ */
+ kNone_BlendOpt = 0,
+ /**
+ * Don't draw at all
+ */
+ kSkipDraw_BlendOptFlag = 0x1,
+ /**
+ * Emit the src color, disable HW blending (replace dst with src)
+ */
+ kDisableBlend_BlendOptFlag = 0x2,
+ /**
+ * The coverage value does not have to be computed separately from alpha, the the output
+ * color can be the modulation of the two.
+ */
+ kCoverageAsAlpha_BlendOptFlag = 0x4,
+ /**
+ * Instead of emitting a src color, emit coverage in the alpha channel and r,g,b are
+ * "don't cares".
+ */
+ kEmitCoverage_BlendOptFlag = 0x8,
+ /**
+ * Emit transparent black instead of the src color, no need to compute coverage.
+ */
+ kEmitTransBlack_BlendOptFlag = 0x10,
+ };
+ GR_DECL_BITFIELD_OPS_FRIENDS(BlendOptFlags);
+
+ /**
+ * Determines what optimizations can be applied based on the blend. The coefficients may have
+ * to be tweaked in order for the optimization to work. srcCoeff and dstCoeff are optional
+ * params that receive the tweaked coefficients. Normally the function looks at the current
+ * state to see if coverage is enabled. By setting forceCoverage the caller can speculatively
+ * determine the blend optimizations that would be used if there was partial pixel coverage.
+ *
+ * Subclasses of GrDrawTarget that actually draw (as opposed to those that just buffer for
+ * playback) must call this function and respect the flags that replace the output color.
+ */
+ BlendOptFlags getBlendOpts(bool forceCoverage = false,
+ GrBlendCoeff* srcCoeff = NULL,
+ GrBlendCoeff* dstCoeff = NULL) const;
+
/// @}
///////////////////////////////////////////////////////////////////////////
@@ -1278,4 +1332,6 @@
typedef GrRefCnt INHERITED;
};
+GR_MAKE_BITFIELD_OPS(GrDrawState::BlendOptFlags);
+
#endif