expand SkShader's flag kConstInY to 16 and 32 variants, allowing a shader

(like gradients) to support predithering. If they do, then they would suppress
kConstInY16, since they no longer are const.

The blitters now check for each flag separately, so we don't have to give up
const-in-Y in the 32bit case, since in that mode we don't care about dithering.



git-svn-id: http://skia.googlecode.com/svn/trunk@339 2bbb7eff-a529-9590-31e7-b0007b416f81

1 files changed, 25 insertions, 100 deletions

diff --git a/src/effects/SkGradientShader.cpp b/src/effects/SkGradientShader.cpp
index 635e0e579f..860e902dd2 100644
--- a/src/effects/SkGradientShader.cpp
+++ b/src/effects/SkGradientShader.cpp
@@ -20,18 +20,6 @@
 #include "SkUnitMapper.h"
 #include "SkUtils.h"
 
-/*
-    ToDo
-
-    - not sure we still need the full Rec struct, now that we're using a cache
-    - detect const-alpha (but not opaque) in getFlags()
-*/
-
-/* dither seems to look better, but not stuningly yet, and it slows us down a little
-    so its not on by default yet.
-*/
-#define TEST_GRADIENT_DITHER
-
 ///////////////////////////////////////////////////////////////////////////
 
 typedef SkFixed (*TileProc)(SkFixed);
@@ -503,12 +491,9 @@ static inline U16CPU dot6to16(unsigned x) {
 
 const uint16_t* Gradient_Shader::getCache16() {
     if (fCache16 == NULL) {
-        if (fCache16Storage == NULL) // set the storage and our working ptr
-#ifdef TEST_GRADIENT_DITHER
+        if (fCache16Storage == NULL) { // set the storage and our working ptr
             fCache16Storage = (uint16_t*)sk_malloc_throw(sizeof(uint16_t) * kCache16Count * 2);
-#else
-            fCache16Storage = (uint16_t*)sk_malloc_throw(sizeof(uint16_t) * kCache16Count);
-#endif
+        }
         fCache16 = fCache16Storage;
         if (fColorCount == 2) {
             build_16bit_cache(fCache16, fOrigColors[0], fOrigColors[1], kCache16Count);
@@ -527,20 +512,14 @@ const uint16_t* Gradient_Shader::getCache16() {
         }
 
         if (fMapper) {
-#ifdef TEST_GRADIENT_DITHER
             fCache16Storage = (uint16_t*)sk_malloc_throw(sizeof(uint16_t) * kCache16Count * 2);
-#else
-            fCache16Storage = (uint16_t*)sk_malloc_throw(sizeof(uint16_t) * kCache16Count);
-#endif
             uint16_t* linear = fCache16;         // just computed linear data
             uint16_t* mapped = fCache16Storage;  // storage for mapped data
             SkUnitMapper* map = fMapper;
             for (int i = 0; i < 64; i++) {
                 int index = map->mapUnit16(dot6to16(i)) >> 10;
                 mapped[i] = linear[index];
-#ifdef TEST_GRADIENT_DITHER
                 mapped[i + 64] = linear[index + 64];
-#endif
             }
             sk_free(fCache16);
             fCache16 = fCache16Storage;
@@ -655,7 +634,13 @@ bool Linear_Gradient::setContext(const SkBitmap& device, const SkPaint& paint,
 
     unsigned mask = SkMatrix::kTranslate_Mask | SkMatrix::kScale_Mask;
     if ((fDstToIndex.getType() & ~mask) == 0) {
-        fFlags |= SkShader::kConstInY_Flag;
+        fFlags |= SkShader::kConstInY32_Flag;
+        if ((fFlags & SkShader::kHasSpan16_Flag) && !paint.isDither()) {
+            // only claim this if we do have a 16bit mode (i.e. none of our
+            // colors have alpha), and if we are not dithering (which obviously
+            // is not const in Y).
+            fFlags |= SkShader::kConstInY16_Flag;
+        }
     }
     return true;
 }
@@ -779,11 +764,9 @@ bool Linear_Gradient::asABitmap(SkBitmap* bitmap, SkMatrix* matrix,
     return true;
 }
 
-#ifdef TEST_GRADIENT_DITHER
-static void dither_memset16(uint16_t dst[], uint16_t value, uint16_t other, int count)
-{
-    if (reinterpret_cast<uintptr_t>(dst) & 2)
-    {
+static void dither_memset16(uint16_t dst[], uint16_t value, uint16_t other,
+                            int count) {
+    if (reinterpret_cast<uintptr_t>(dst) & 2) {
         *dst++ = value;
         count -= 1;
         SkTSwap(value, other);
@@ -791,10 +774,10 @@ static void dither_memset16(uint16_t dst[], uint16_t value, uint16_t other, int
 
     sk_memset32((uint32_t*)dst, (value << 16) | other, count >> 1);
     
-    if (count & 1)
+    if (count & 1) {
         dst[count - 1] = value;
+    }
 }
-#endif
 
 void Linear_Gradient::shadeSpan16(int x, int y, uint16_t dstC[], int count)
 {
@@ -804,9 +787,7 @@ void Linear_Gradient::shadeSpan16(int x, int y, uint16_t dstC[], int count)
     SkMatrix::MapXYProc dstProc = fDstToIndexProc;
     TileProc            proc = fTileProc;
     const uint16_t*     cache = this->getCache16();
-#ifdef TEST_GRADIENT_DITHER
     int                 toggle = ((x ^ y) & 1) << kCache16Bits;
-#endif
 
     if (fDstToIndexClass != kPerspective_MatrixClass) {
         dstProc(fDstToIndex, SkIntToScalar(x), SkIntToScalar(y), &srcPt);
@@ -827,34 +808,22 @@ void Linear_Gradient::shadeSpan16(int x, int y, uint16_t dstC[], int count)
             // we're a vertical gradient, so no change in a span
             unsigned fi = proc(fx) >> 10;
             SkASSERT(fi <= 63);
-#ifdef TEST_GRADIENT_DITHER
             dither_memset16(dstC, cache[toggle + fi], cache[(toggle ^ (1 << kCache16Bits)) + fi], count);
-#else
-            sk_memset16(dstC, cache[fi], count);
-#endif
         } else if (proc == clamp_tileproc) {
             do {
                 unsigned fi = SkClampMax(fx >> 10, 63);
                 SkASSERT(fi <= 63);
                 fx += dx;
-#ifdef TEST_GRADIENT_DITHER
                 *dstC++ = cache[toggle + fi];
                 toggle ^= (1 << kCache16Bits);
-#else
-                *dstC++ = cache[fi];
-#endif
             } while (--count != 0);
         } else if (proc == mirror_tileproc) {
             do {
                 unsigned fi = mirror_6bits(fx >> 10);
                 SkASSERT(fi <= 0x3F);
                 fx += dx;
-#ifdef TEST_GRADIENT_DITHER
                 *dstC++ = cache[toggle + fi];
                 toggle ^= (1 << kCache16Bits);
-#else
-                *dstC++ = cache[fi];
-#endif
             } while (--count != 0);
         } else {
             SkASSERT(proc == repeat_tileproc);
@@ -862,12 +831,8 @@ void Linear_Gradient::shadeSpan16(int x, int y, uint16_t dstC[], int count)
                 unsigned fi = repeat_6bits(fx >> 10);
                 SkASSERT(fi <= 0x3F);
                 fx += dx;
-#ifdef TEST_GRADIENT_DITHER
                 *dstC++ = cache[toggle + fi];
                 toggle ^= (1 << kCache16Bits);
-#else
-                *dstC++ = cache[fi];
-#endif
             } while (--count != 0);
         }
     } else {
@@ -879,12 +844,8 @@ void Linear_Gradient::shadeSpan16(int x, int y, uint16_t dstC[], int count)
             SkASSERT(fi <= 0xFFFF);
 
             int index = fi >> (16 - kCache16Bits);
-#ifdef TEST_GRADIENT_DITHER
             *dstC++ = cache[toggle + index];
             toggle ^= (1 << kCache16Bits);
-#else
-            *dstC++ = cache[index];
-#endif
 
             dstX += SK_Scalar1;
         } while (--count != 0);
@@ -1033,40 +994,33 @@ public:
             } while (--count != 0);
         }
     }
-    virtual void shadeSpan16(int x, int y, uint16_t dstC[], int count)
-    {
+
+    virtual void shadeSpan16(int x, int y, uint16_t dstC[], int count) {
         SkASSERT(count > 0);
 
         SkPoint             srcPt;
         SkMatrix::MapXYProc dstProc = fDstToIndexProc;
         TileProc            proc = fTileProc;
         const uint16_t*     cache = this->getCache16();
-#ifdef TEST_GRADIENT_DITHER
         int                 toggle = ((x ^ y) & 1) << kCache16Bits;
-#endif
 
-        if (fDstToIndexClass != kPerspective_MatrixClass)
-        {
+        if (fDstToIndexClass != kPerspective_MatrixClass) {
             dstProc(fDstToIndex, SkIntToScalar(x), SkIntToScalar(y), &srcPt);
             SkFixed dx, fx = SkScalarToFixed(srcPt.fX);
             SkFixed dy, fy = SkScalarToFixed(srcPt.fY);
 
-            if (fDstToIndexClass == kFixedStepInX_MatrixClass)
-            {
+            if (fDstToIndexClass == kFixedStepInX_MatrixClass) {
                 SkFixed storage[2];
                 (void)fDstToIndex.fixedStepInX(SkIntToScalar(y), &storage[0], &storage[1]);
                 dx = storage[0];
                 dy = storage[1];
-            }
-            else
-            {
+            } else {
                 SkASSERT(fDstToIndexClass == kLinear_MatrixClass);
                 dx = SkScalarToFixed(fDstToIndex.getScaleX());
                 dy = SkScalarToFixed(fDstToIndex.getSkewY());
             }
 
-            if (proc == clamp_tileproc)
-            {
+            if (proc == clamp_tileproc) {
                 const uint8_t* sqrt_table = gSqrt8Table;
 
                 /* knock these down so we can pin against +- 0x7FFF, which is an immediate load,
@@ -1079,8 +1033,7 @@ public:
                 dx >>= 1;
                 fy >>= 1;
                 dy >>= 1;
-                if (dy == 0)    // might perform this check for the other modes, but the win will be a smaller % of the total
-                {
+                if (dy == 0) {    // might perform this check for the other modes, but the win will be a smaller % of the total
                     fy = SkPin32(fy, -0xFFFF >> 1, 0xFFFF >> 1);
                     fy *= fy;
                     do {
@@ -1088,16 +1041,10 @@ public:
                         unsigned fi = (xx * xx + fy) >> (14 + 16 - kSQRT_TABLE_BITS);
                         fi = SkFastMin32(fi, 0xFFFF >> (16 - kSQRT_TABLE_BITS));
                         fx += dx;
-#ifdef TEST_GRADIENT_DITHER
                         *dstC++ = cache[toggle + (sqrt_table[fi] >> (8 - kCache16Bits))];
                         toggle ^= (1 << kCache16Bits);
-#else
-                        *dstC++ = cache[sqrt_table[fi] >> (8 - kCache16Bits)];
-#endif
                     } while (--count != 0);
-                }
-                else
-                {
+                } else {
                     do {
                         unsigned xx = SkPin32(fx, -0xFFFF >> 1, 0xFFFF >> 1);
                         unsigned fi = SkPin32(fy, -0xFFFF >> 1, 0xFFFF >> 1);
@@ -1105,33 +1052,21 @@ public:
                         fi = SkFastMin32(fi, 0xFFFF >> (16 - kSQRT_TABLE_BITS));
                         fx += dx;
                         fy += dy;
-#ifdef TEST_GRADIENT_DITHER
                         *dstC++ = cache[toggle + (sqrt_table[fi] >> (8 - kCache16Bits))];
                         toggle ^= (1 << kCache16Bits);
-#else
-                        *dstC++ = cache[sqrt_table[fi] >> (8 - kCache16Bits)];
-#endif
                     } while (--count != 0);
                 }
-            }
-            else if (proc == mirror_tileproc)
-            {
+            } else if (proc == mirror_tileproc) {
                 do {
                     SkFixed dist = SkFixedSqrt(SkFixedSquare(fx) + SkFixedSquare(fy));
                     unsigned fi = mirror_tileproc(dist);
                     SkASSERT(fi <= 0xFFFF);
                     fx += dx;
                     fy += dy;
-#ifdef TEST_GRADIENT_DITHER
                     *dstC++ = cache[toggle + (fi >> (16 - kCache16Bits))];
                     toggle ^= (1 << kCache16Bits);
-#else
-                    *dstC++ = cache[fi >> (16 - kCache16Bits)];
-#endif
                 } while (--count != 0);
-            }
-            else
-            {
+            } else {
                 SkASSERT(proc == repeat_tileproc);
                 do {
                     SkFixed dist = SkFixedSqrt(SkFixedSquare(fx) + SkFixedSquare(fy));
@@ -1139,17 +1074,11 @@ public:
                     SkASSERT(fi <= 0xFFFF);
                     fx += dx;
                     fy += dy;
-#ifdef TEST_GRADIENT_DITHER
                     *dstC++ = cache[toggle + (fi >> (16 - kCache16Bits))];
                     toggle ^= (1 << kCache16Bits);
-#else
-                    *dstC++ = cache[fi >> (16 - kCache16Bits)];
-#endif
                 } while (--count != 0);
             }
-        }
-        else    // perspective case
-        {
+        } else {    // perspective case
             SkScalar dstX = SkIntToScalar(x);
             SkScalar dstY = SkIntToScalar(y);
             do {
@@ -1158,12 +1087,8 @@ public:
                 SkASSERT(fi <= 0xFFFF);
 
                 int index = fi >> (16 - kCache16Bits);
-#ifdef TEST_GRADIENT_DITHER
                 *dstC++ = cache[toggle + index];
                 toggle ^= (1 << kCache16Bits);
-#else
-                *dstC++ = cache[index];
-#endif
 
                 dstX += SK_Scalar1;
             } while (--count != 0);