Move dither toggle logic into common helper functions, to make it easier to

change their behavior later. No functional change.
Review URL: https://codereview.appspot.com/7241063

git-svn-id: http://skia.googlecode.com/svn/trunk@7525 2bbb7eff-a529-9590-31e7-b0007b416f81

4 files changed, 47 insertions, 31 deletions

diff --git a/src/effects/gradients/SkGradientShaderPriv.h b/src/effects/gradients/SkGradientShaderPriv.h
index d35fb1c596..4d14dc6a07 100644
--- a/src/effects/gradients/SkGradientShaderPriv.h
+++ b/src/effects/gradients/SkGradientShaderPriv.h
@@ -175,6 +175,22 @@ private:
     typedef SkShader INHERITED;
 };
 
+static inline int init_dither_toggle(int x, int y) {
+    return ((x ^ y) & 1) * SkGradientShaderBase::kDitherStride32;
+}
+
+static inline int next_dither_toggle(int toggle) {
+    return toggle ^ SkGradientShaderBase::kDitherStride32;
+}
+
+static inline int init_dither_toggle16(int x, int y) {
+    return ((x ^ y) & 1) * SkGradientShaderBase::kDitherStride16;
+}
+
+static inline int next_dither_toggle16(int toggle) {
+    return toggle ^ SkGradientShaderBase::kDitherStride16;
+}
+
 ///////////////////////////////////////////////////////////////////////////////
 
 #if SK_SUPPORT_GPU
diff --git a/src/effects/gradients/SkLinearGradient.cpp b/src/effects/gradients/SkLinearGradient.cpp
index b194d50a84..0d3cc7e0be 100644
--- a/src/effects/gradients/SkLinearGradient.cpp
+++ b/src/effects/gradients/SkLinearGradient.cpp
@@ -111,7 +111,7 @@ bool SkLinearGradient::setContext(const SkBitmap& device, const SkPaint& paint,
     SkASSERT(fi <= 0xFF);           \
     fx += dx;                       \
     *dstC++ = cache[toggle + fi];   \
-    toggle ^= SkGradientShaderBase::kDitherStride32; \
+    toggle = next_dither_toggle(toggle); \
     } while (0)
 
 namespace {
@@ -156,7 +156,7 @@ void shadeSpan_linear_clamp(TileProc proc, SkFixed dx, SkFixed fx,
     if ((count = range.fCount0) > 0) {
         sk_memset32_dither(dstC,
             cache[toggle + range.fV0],
-            cache[(toggle ^ SkGradientShaderBase::kDitherStride32) + range.fV0],
+            cache[next_dither_toggle(toggle) + range.fV0],
             count);
         dstC += count;
     }
@@ -178,7 +178,7 @@ void shadeSpan_linear_clamp(TileProc proc, SkFixed dx, SkFixed fx,
     if ((count = range.fCount2) > 0) {
         sk_memset32_dither(dstC,
             cache[toggle + range.fV1],
-            cache[(toggle ^ SkGradientShaderBase::kDitherStride32) + range.fV1],
+            cache[next_dither_toggle(toggle) + range.fV1],
             count);
     }
 }
@@ -192,7 +192,7 @@ void shadeSpan_linear_mirror(TileProc proc, SkFixed dx, SkFixed fx,
         SkASSERT(fi <= 0xFF);
         fx += dx;
         *dstC++ = cache[toggle + fi];
-        toggle ^= SkGradientShaderBase::kDitherStride32;
+        toggle = next_dither_toggle(toggle);
     } while (--count != 0);
 }
 
@@ -205,7 +205,7 @@ void shadeSpan_linear_repeat(TileProc proc, SkFixed dx, SkFixed fx,
         SkASSERT(fi <= 0xFF);
         fx += dx;
         *dstC++ = cache[toggle + fi];
-        toggle ^= SkGradientShaderBase::kDitherStride32;
+        toggle = next_dither_toggle(toggle);
     } while (--count != 0);
 }
 
@@ -220,7 +220,7 @@ void SkLinearGradient::shadeSpan(int x, int y, SkPMColor* SK_RESTRICT dstC,
     TileProc            proc = fTileProc;
     const SkPMColor* SK_RESTRICT cache = this->getCache32();
 #ifdef USE_DITHER_32BIT_GRADIENT
-    int                 toggle = ((x ^ y) & 1) * kDitherStride32;
+    int                 toggle = init_dither_toggle(x, y);
 #else
     int toggle = 0;
 #endif
@@ -258,7 +258,7 @@ void SkLinearGradient::shadeSpan(int x, int y, SkPMColor* SK_RESTRICT dstC,
             unsigned fi = proc(SkScalarToFixed(srcPt.fX));
             SkASSERT(fi <= 0xFFFF);
             *dstC++ = cache[toggle + (fi >> kCache32Shift)];
-            toggle ^= SkGradientShaderBase::kDitherStride32;
+            toggle = next_dither_toggle(toggle);
             dstX += SK_Scalar1;
         } while (--count != 0);
     }
@@ -310,7 +310,7 @@ static void dither_memset16(uint16_t dst[], uint16_t value, uint16_t other,
     SkASSERT(fi < SkGradientShaderBase::kCache16Count);       \
     fx += dx;                           \
     *dstC++ = cache[toggle + fi];       \
-    toggle ^= SkGradientShaderBase::kDitherStride16;            \
+    toggle = next_dither_toggle16(toggle);            \
     } while (0)
 
 namespace {
@@ -327,7 +327,7 @@ void shadeSpan16_linear_vertical(TileProc proc, SkFixed dx, SkFixed fx,
     unsigned fi = proc(fx) >> SkGradientShaderBase::kCache16Shift;
     SkASSERT(fi < SkGradientShaderBase::kCache16Count);
     dither_memset16(dstC, cache[toggle + fi],
-        cache[(toggle ^ SkGradientShaderBase::kDitherStride16) + fi], count);
+        cache[next_dither_toggle16(toggle) + fi], count);
 
 }
 
@@ -341,7 +341,7 @@ void shadeSpan16_linear_clamp(TileProc proc, SkFixed dx, SkFixed fx,
     if ((count = range.fCount0) > 0) {
         dither_memset16(dstC,
             cache[toggle + range.fV0],
-            cache[(toggle ^ SkGradientShaderBase::kDitherStride16) + range.fV0],
+            cache[next_dither_toggle16(toggle) + range.fV0],
             count);
         dstC += count;
     }
@@ -363,7 +363,7 @@ void shadeSpan16_linear_clamp(TileProc proc, SkFixed dx, SkFixed fx,
     if ((count = range.fCount2) > 0) {
         dither_memset16(dstC,
             cache[toggle + range.fV1],
-            cache[(toggle ^ SkGradientShaderBase::kDitherStride16) + range.fV1],
+            cache[next_dither_toggle16(toggle) + range.fV1],
             count);
     }
 }
@@ -378,7 +378,7 @@ void shadeSpan16_linear_mirror(TileProc proc, SkFixed dx, SkFixed fx,
         SkASSERT(fi < SkGradientShaderBase::kCache16Count);
         fx += dx;
         *dstC++ = cache[toggle + fi];
-        toggle ^= SkGradientShaderBase::kDitherStride16;
+        toggle = next_dither_toggle16(toggle);
     } while (--count != 0);
 }
 
@@ -392,7 +392,7 @@ void shadeSpan16_linear_repeat(TileProc proc, SkFixed dx, SkFixed fx,
         SkASSERT(fi < SkGradientShaderBase::kCache16Count);
         fx += dx;
         *dstC++ = cache[toggle + fi];
-        toggle ^= SkGradientShaderBase::kDitherStride16;
+        toggle = next_dither_toggle16(toggle);
     } while (--count != 0);
 }
 }
@@ -405,7 +405,7 @@ void SkLinearGradient::shadeSpan16(int x, int y,
     SkMatrix::MapXYProc dstProc = fDstToIndexProc;
     TileProc            proc = fTileProc;
     const uint16_t* SK_RESTRICT cache = this->getCache16();
-    int                 toggle = ((x ^ y) & 1) * kDitherStride16;
+    int                 toggle = init_dither_toggle16(x, y);
 
     if (fDstToIndexClass != kPerspective_MatrixClass) {
         dstProc(fDstToIndex, SkIntToScalar(x) + SK_ScalarHalf,
@@ -442,7 +442,7 @@ void SkLinearGradient::shadeSpan16(int x, int y,
 
             int index = fi >> kCache16Shift;
             *dstC++ = cache[toggle + index];
-            toggle ^= SkGradientShaderBase::kDitherStride16;
+            toggle = next_dither_toggle16(toggle);
 
             dstX += SK_Scalar1;
         } while (--count != 0);
diff --git a/src/effects/gradients/SkRadialGradient.cpp b/src/effects/gradients/SkRadialGradient.cpp
index 6945d5a8cc..328fe76e51 100644
--- a/src/effects/gradients/SkRadialGradient.cpp
+++ b/src/effects/gradients/SkRadialGradient.cpp
@@ -88,7 +88,7 @@ void shadeSpan16_radial_clamp(SkScalar sfx, SkScalar sdx,
             fx += dx;
             *dstC++ = cache[toggle +
                             (sqrt_table[fi] >> SkGradientShaderBase::kSqrt16Shift)];
-            toggle ^= SkGradientShaderBase::kDitherStride16;
+            toggle = next_dither_toggle16(toggle);
         } while (--count != 0);
     } else {
         do {
@@ -100,7 +100,7 @@ void shadeSpan16_radial_clamp(SkScalar sfx, SkScalar sdx,
             fy += dy;
             *dstC++ = cache[toggle +
                             (sqrt_table[fi] >> SkGradientShaderBase::kSqrt16Shift)];
-            toggle ^= SkGradientShaderBase::kDitherStride16;
+            toggle = next_dither_toggle16(toggle);
         } while (--count != 0);
     }
 }
@@ -123,7 +123,7 @@ void shadeSpan16_radial_mirror(SkScalar sfx, SkScalar sdx,
         unsigned fi = mirror_tileproc(dist);
         SkASSERT(fi <= 0xFFFF);
         *dstC++ = cache[toggle + (fi >> SkGradientShaderBase::kCache16Shift)];
-        toggle ^= SkGradientShaderBase::kDitherStride16;
+        toggle = next_dither_toggle16(toggle);
         sfx += sdx;
         sfy += sdy;
     } while (--count != 0);
@@ -144,7 +144,7 @@ void shadeSpan16_radial_repeat(SkScalar sfx, SkScalar sdx,
         fx += dx;
         fy += dy;
         *dstC++ = cache[toggle + (fi >> SkGradientShaderBase::kCache16Shift)];
-        toggle ^= SkGradientShaderBase::kDitherStride16;
+        toggle = next_dither_toggle16(toggle);
     } while (--count != 0);
 }
 
@@ -175,7 +175,7 @@ void SkRadialGradient::shadeSpan16(int x, int y, uint16_t* dstCParam,
     SkMatrix::MapXYProc dstProc = fDstToIndexProc;
     TileProc            proc = fTileProc;
     const uint16_t* SK_RESTRICT cache = this->getCache16();
-    int                 toggle = ((x ^ y) & 1) * kDitherStride16;
+    int                 toggle = init_dither_toggle16(x, y);
 
     if (fDstToIndexClass != kPerspective_MatrixClass) {
         dstProc(fDstToIndex, SkIntToScalar(x) + SK_ScalarHalf,
@@ -214,7 +214,7 @@ void SkRadialGradient::shadeSpan16(int x, int y, uint16_t* dstCParam,
 
             int index = fi >> (16 - kCache16Bits);
             *dstC++ = cache[toggle + index];
-            toggle ^= kDitherStride16;
+            toggle = next_dither_toggle16(toggle);
 
             dstX += SK_Scalar1;
         } while (--count != 0);
@@ -296,7 +296,7 @@ inline bool no_need_for_radial_pin(int fx, int dx,
     fi = (fx * fx + fy * fy) >> (14 + 16 - kSQRT_TABLE_BITS); \
     *dstC++ = cache[toggle + \
                     (sqrt_table[fi] >> SkGradientShaderBase::kSqrt32Shift)]; \
-    toggle ^= SkGradientShaderBase::kDitherStride32; \
+    toggle = next_dither_toggle(toggle); \
     fx += dx; \
     fy += dy;
 
@@ -321,7 +321,7 @@ void shadeSpan_radial_clamp(SkScalar sfx, SkScalar sdx,
         unsigned fi = SkGradientShaderBase::kCache32Count - 1;
         sk_memset32_dither(dstC,
             cache[toggle + fi],
-            cache[(toggle ^ SkGradientShaderBase::kDitherStride32) + fi],
+            cache[next_dither_toggle(toggle) + fi],
             count);
     } else if ((count > 4) &&
                no_need_for_radial_pin(fx, dx, fy, dy, count)) {
@@ -347,7 +347,7 @@ void shadeSpan_radial_clamp(SkScalar sfx, SkScalar sdx,
                 fi = SkFastMin32(fi, 0xFFFF >> (16 - kSQRT_TABLE_BITS));
                 *dstC++ = cache[toggle + (sqrt_table[fi] >>
                     SkGradientShaderBase::kSqrt32Shift)];
-                toggle ^= SkGradientShaderBase::kDitherStride32;
+                toggle = next_dither_toggle(toggle);
                 fx += dx;
             } while (--count != 0);
         } else {
@@ -358,7 +358,7 @@ void shadeSpan_radial_clamp(SkScalar sfx, SkScalar sdx,
                 fi = SkFastMin32(fi, 0xFFFF >> (16 - kSQRT_TABLE_BITS));
                 *dstC++ = cache[toggle + (sqrt_table[fi] >>
                     SkGradientShaderBase::kSqrt32Shift)];
-                toggle ^= SkGradientShaderBase::kDitherStride32;
+                toggle = next_dither_toggle(toggle);
                 fx += dx;
                 fy += dy;
             } while (--count != 0);
@@ -387,7 +387,7 @@ void shadeSpan_radial_mirror(SkScalar sfx, SkScalar sdx,
         unsigned fi = mirror_tileproc(dist);
         SkASSERT(fi <= 0xFFFF);
         *dstC++ = cache[toggle + (fi >> SkGradientShaderBase::kCache32Shift)];
-        toggle ^= SkGradientShaderBase::kDitherStride32;
+        toggle = next_dither_toggle(toggle);
         sfx += sdx;
         sfy += sdy;
     } while (--count != 0);
@@ -410,7 +410,7 @@ void shadeSpan_radial_repeat(SkScalar sfx, SkScalar sdx,
         unsigned fi = repeat_tileproc(dist);
         SkASSERT(fi <= 0xFFFF);
         *dstC++ = cache[toggle + (fi >> SkGradientShaderBase::kCache32Shift)];
-        toggle ^= SkGradientShaderBase::kDitherStride32;
+        toggle = next_dither_toggle(toggle);
         fx += dx;
         fy += dy;
     } while (--count != 0);
@@ -426,7 +426,7 @@ void SkRadialGradient::shadeSpan(int x, int y,
     TileProc            proc = fTileProc;
     const SkPMColor* SK_RESTRICT cache = this->getCache32();
 #ifdef USE_DITHER_32BIT_GRADIENT
-    int toggle = ((x ^ y) & 1) * SkGradientShaderBase::kDitherStride32;
+    int toggle = init_dither_toggle(x, y);
 #else
     int toggle = 0;
 #endif
diff --git a/src/effects/gradients/SkSweepGradient.cpp b/src/effects/gradients/SkSweepGradient.cpp
index 3cdac8577b..db18521066 100644
--- a/src/effects/gradients/SkSweepGradient.cpp
+++ b/src/effects/gradients/SkSweepGradient.cpp
@@ -337,7 +337,7 @@ void SkSweepGradient::shadeSpan16(int x, int y, uint16_t* SK_RESTRICT dstC,
     SkMatrix::MapXYProc proc = fDstToIndexProc;
     const SkMatrix&     matrix = fDstToIndex;
     const uint16_t* SK_RESTRICT cache = this->getCache16();
-    int                 toggle = ((x ^ y) & 1) * kDitherStride16;
+    int                 toggle = init_dither_toggle16(x, y);
     SkPoint             srcPt;
 
     if (fDstToIndexClass != kPerspective_MatrixClass) {
@@ -361,7 +361,7 @@ void SkSweepGradient::shadeSpan16(int x, int y, uint16_t* SK_RESTRICT dstC,
         for (; count > 0; --count) {
             int index = SkATan2_255(fy, fx) >> (8 - kCache16Bits);
             *dstC++ = cache[toggle + index];
-            toggle ^= kDitherStride16;
+            toggle = next_dither_toggle16(toggle);
             fx += dx;
             fy += dy;
         }
@@ -373,7 +373,7 @@ void SkSweepGradient::shadeSpan16(int x, int y, uint16_t* SK_RESTRICT dstC,
             int index = SkATan2_255(srcPt.fY, srcPt.fX);
             index >>= (8 - kCache16Bits);
             *dstC++ = cache[toggle + index];
-            toggle ^= kDitherStride16;
+            toggle = next_dither_toggle16(toggle);
         }
     }
 }