Implement Porter Duff XP with a blend table

src/gpu/GrBlend.cpp

Index: src/gpu/GrBlend.cpp
diff --git a/src/gpu/GrBlend.cpp b/src/gpu/GrBlend.cpp
deleted file mode 100644
index 52e335e9b0461cd7132ce97abdcb26cb0f91dbef..0000000000000000000000000000000000000000
--- a/src/gpu/GrBlend.cpp
+++ /dev/null
@@ -1,154 +0,0 @@
-
-/*
- * Copyright 2013 Google Inc.
- *
- * Use of this source code is governed by a BSD-style license that can be
- * found in the LICENSE file.
- */
-
-#include "GrBlend.h"
-
-static inline GrBlendCoeff swap_coeff_src_dst(GrBlendCoeff coeff) {
-    switch (coeff) {
-        case kDC_GrBlendCoeff:
-            return kSC_GrBlendCoeff;
-        case kIDC_GrBlendCoeff:
-            return kISC_GrBlendCoeff;
-        case kDA_GrBlendCoeff:
-            return kSA_GrBlendCoeff;
-        case kIDA_GrBlendCoeff:
-            return kISA_GrBlendCoeff;
-        case kSC_GrBlendCoeff:
-            return kDC_GrBlendCoeff;
-        case kISC_GrBlendCoeff:
-            return kIDC_GrBlendCoeff;
-        case kSA_GrBlendCoeff:
-            return kDA_GrBlendCoeff;
-        case kISA_GrBlendCoeff:
-            return kIDA_GrBlendCoeff;
-        default:
-            return coeff;
-    }
-}
-
-static inline unsigned saturated_add(unsigned a, unsigned b) {
-    SkASSERT(a <= 255);
-    SkASSERT(b <= 255);
-    unsigned sum = a + b;
-    if (sum > 255) {
-        sum = 255;
-    }
-    return sum;
-}
-
-static GrColor add_colors(GrColor src, GrColor dst) {
-    unsigned r = saturated_add(GrColorUnpackR(src), GrColorUnpackR(dst));
-    unsigned g = saturated_add(GrColorUnpackG(src), GrColorUnpackG(dst));
-    unsigned b = saturated_add(GrColorUnpackB(src), GrColorUnpackB(dst));
-    unsigned a = saturated_add(GrColorUnpackA(src), GrColorUnpackA(dst));
-    return GrColorPackRGBA(r, g, b, a);
-}
-
-static inline bool valid_color(uint32_t compFlags) {
-     return (kRGBA_GrColorComponentFlags & compFlags) == kRGBA_GrColorComponentFlags;
-}
-
-static GrColor simplify_blend_term(GrBlendCoeff* srcCoeff,
-                                   GrColor srcColor, uint32_t srcCompFlags,
-                                   GrColor dstColor, uint32_t dstCompFlags,
-                                   GrColor constantColor) {
-
-    SkASSERT(!GrBlendCoeffRefsSrc(*srcCoeff));
-    SkASSERT(srcCoeff);
-
-    // Check whether srcCoeff can be reduced to kOne or kZero based on known color inputs.
-    // We could pick out the coeff r,g,b,a values here and use them to compute the blend term color,
-    // if possible, below but that is not implemented now.
-    switch (*srcCoeff) {
-        case kIDC_GrBlendCoeff:
-            dstColor = ~dstColor; // fallthrough
-        case kDC_GrBlendCoeff:
-            if (valid_color(dstCompFlags)) {
-                if (0xffffffff == dstColor) {
-                    *srcCoeff = kOne_GrBlendCoeff;
-                } else if (0 == dstColor) {
-                    *srcCoeff = kZero_GrBlendCoeff;
-                }
-            }
-            break;
-
-        case kIDA_GrBlendCoeff:
-            dstColor = ~dstColor; // fallthrough
-        case kDA_GrBlendCoeff:
-            if (kA_GrColorComponentFlag & dstCompFlags) {
-                if (0xff == GrColorUnpackA(dstColor)) {
-                    *srcCoeff = kOne_GrBlendCoeff;
-                } else if (0 == GrColorUnpackA(dstColor)) {
-                    *srcCoeff = kZero_GrBlendCoeff;
-                }
-            }
-            break;
-
-        case kIConstC_GrBlendCoeff:
-            constantColor = ~constantColor; // fallthrough
-        case kConstC_GrBlendCoeff:
-            if (0xffffffff == constantColor) {
-                *srcCoeff = kOne_GrBlendCoeff;
-            } else if (0 == constantColor) {
-                *srcCoeff = kZero_GrBlendCoeff;
-            }
-            break;
-
-        case kIConstA_GrBlendCoeff:
-            constantColor = ~constantColor; // fallthrough
-        case kConstA_GrBlendCoeff:
-            if (0xff == GrColorUnpackA(constantColor)) {
-                *srcCoeff = kOne_GrBlendCoeff;
-            } else if (0 == GrColorUnpackA(constantColor)) {
-                *srcCoeff = kZero_GrBlendCoeff;
-            }
-            break;
-
-        default:
-            break;
-    }
-    // We may have invalidated these above and shouldn't read them again.
-    SkDEBUGCODE(dstColor = constantColor = GrColor_ILLEGAL;)
-
-    if (kZero_GrBlendCoeff == *srcCoeff || (valid_color(srcCompFlags) && 0 == srcColor)) {
-        *srcCoeff = kZero_GrBlendCoeff;
-        return 0;
-    }
-
-    if (kOne_GrBlendCoeff == *srcCoeff && valid_color(srcCompFlags)) {
-        return srcColor;
-    } else {
-        return GrColor_ILLEGAL;
-    }
-}
-
-GrColor GrSimplifyBlend(GrBlendCoeff* srcCoeff,
-                        GrBlendCoeff* dstCoeff,
-                        GrColor srcColor, uint32_t srcCompFlags,
-                        GrColor dstColor, uint32_t dstCompFlags,
-                        GrColor constantColor) {
-    GrColor srcTermColor = simplify_blend_term(srcCoeff,
-                                               srcColor, srcCompFlags,
-                                               dstColor, dstCompFlags,
-                                               constantColor);
-
-    // We call the same function to simplify the dst blend coeff. We trick it out by swapping the
-    // src and dst.
-    GrBlendCoeff spoofedCoeff = swap_coeff_src_dst(*dstCoeff);
-    GrColor dstTermColor = simplify_blend_term(&spoofedCoeff,
-                                               dstColor, dstCompFlags,
-                                               srcColor, srcCompFlags,
-                                               constantColor);
-    *dstCoeff = swap_coeff_src_dst(spoofedCoeff);
-
-    if (GrColor_ILLEGAL != srcTermColor && GrColor_ILLEGAL != dstTermColor) {
-        return add_colors(srcTermColor, dstTermColor);
-    } else {
-        return GrColor_ILLEGAL;
-    }
-}