Revert of Remove unused (by clients) SkUnitMapper (https://codereview.chromium.org/283273002/)

src/effects/gradients/SkGradientShader.cpp

Index: src/effects/gradients/SkGradientShader.cpp
diff --git a/src/effects/gradients/SkGradientShader.cpp b/src/effects/gradients/SkGradientShader.cpp
index 38e9210cb34c2addbf73f82e359c0dd290f07d6b..d376b2223696d45569d8389dda073ec90e3f1921 100644
--- a/src/effects/gradients/SkGradientShader.cpp
+++ b/src/effects/gradients/SkGradientShader.cpp
@@ -17,6 +17,8 @@
 {
     SkASSERT(desc.fCount > 1);
 
+    fMapper = desc.fMapper;
+    SkSafeRef(fMapper);
     fGradFlags = SkToU8(desc.fGradFlags);
 
     SkASSERT((unsigned)desc.fTileMode < SkShader::kTileModeCount);
@@ -140,10 +142,7 @@
 }
 
 SkGradientShaderBase::SkGradientShaderBase(SkReadBuffer& buffer) : INHERITED(buffer) {
-    if (buffer.isVersionLT(SkReadBuffer::kNoUnitMappers_Version)) {
-        // skip the old SkUnitMapper slot
-        buffer.skipFlattenable();
-    }
+    fMapper = buffer.readUnitMapper();
 
     int colorCount = fColorCount = buffer.getArrayCount();
     if (colorCount > kColorStorageCount) {
@@ -182,6 +181,7 @@
     if (fOrigColors != fStorage) {
         sk_free(fOrigColors);
     }
+    SkSafeUnref(fMapper);
 }
 
 void SkGradientShaderBase::initCommon() {
@@ -194,6 +194,7 @@
 
 void SkGradientShaderBase::flatten(SkWriteBuffer& buffer) const {
     this->INHERITED::flatten(buffer);
+    buffer.writeFlattenable(fMapper);
     buffer.writeColorArray(fOrigColors, fColorCount);
     buffer.writeUInt(pack_mode_flags(fTileMode, fGradFlags));
     if (fColorCount > 2) {
@@ -527,6 +528,20 @@
             prevIndex = nextIndex;
         }
     }
+
+    if (cache->fShader.fMapper) {
+        cache->fCache16Storage = (uint16_t*)sk_malloc_throw(allocSize);
+        uint16_t* linear = cache->fCache16;         // just computed linear data
+        uint16_t* mapped = cache->fCache16Storage;  // storage for mapped data
+        SkUnitMapper* map = cache->fShader.fMapper;
+        for (int i = 0; i < kCache16Count; i++) {
+            int index = map->mapUnit16(bitsTo16(i, kCache16Bits)) >> kCache16Shift;
+            mapped[i] = linear[index];
+            mapped[i + kCache16Count] = linear[index + kCache16Count];
+        }
+        sk_free(cache->fCache16);
+        cache->fCache16 = cache->fCache16Storage;
+    }
 }
 
 const SkPMColor* SkGradientShaderBase::GradientShaderCache::getCache32() {
@@ -564,6 +579,23 @@
             prevIndex = nextIndex;
         }
     }
+
+    if (cache->fShader.fMapper) {
+        SkMallocPixelRef* newPR = SkMallocPixelRef::NewAllocate(info, 0, NULL);
+        SkPMColor* linear = cache->fCache32;           // just computed linear data
+        SkPMColor* mapped = (SkPMColor*)newPR->getAddr();    // storage for mapped data
+        SkUnitMapper* map = cache->fShader.fMapper;
+        for (int i = 0; i < kCache32Count; i++) {
+            int index = map->mapUnit16((i << 8) | i) >> 8;
+            mapped[i + kCache32Count*0] = linear[index + kCache32Count*0];
+            mapped[i + kCache32Count*1] = linear[index + kCache32Count*1];
+            mapped[i + kCache32Count*2] = linear[index + kCache32Count*2];
+            mapped[i + kCache32Count*3] = linear[index + kCache32Count*3];
+        }
+        cache->fCache32PixelRef->unref();
+        cache->fCache32PixelRef = newPR;
+        cache->fCache32 = (SkPMColor*)newPR->getAddr();
+    }
 }
 
 /*
@@ -594,6 +626,15 @@
     // our caller assumes no external alpha, so we ensure that our cache is
     // built with 0xFF
     SkAutoTUnref<GradientShaderCache> cache(this->refCache(0xFF));
+
+    // don't have a way to put the mapper into our cache-key yet
+    if (fMapper) {
+        // force our cache32pixelref to be built
+        (void)cache->getCache32();
+        bitmap->setConfig(SkImageInfo::MakeN32Premul(kCache32Count, 1));
+        bitmap->setPixelRef(cache->getCache32PixelRef());
+        return;
+    }
 
     // build our key: [numColors + colors[] + {positions[]} + flags ]
     int count = 1 + fColorCount + 1;
@@ -703,6 +744,8 @@
     str->append(" ");
     str->append(gTileModeName[fTileMode]);
 
+    // TODO: add "fMapper->toString(str);" when SkUnitMapper::toString is added
+
     this->INHERITED::toString(str);
 }
 #endif
@@ -727,11 +770,13 @@
 static void desc_init(SkGradientShaderBase::Descriptor* desc,
                       const SkColor colors[],
                       const SkScalar pos[], int colorCount,
-                      SkShader::TileMode mode, uint32_t flags) {
+                      SkShader::TileMode mode,
+                      SkUnitMapper* mapper, uint32_t flags) {
     desc->fColors       = colors;
     desc->fPos          = pos;
     desc->fCount        = colorCount;
     desc->fTileMode     = mode;
+    desc->fMapper       = mapper;
     desc->fGradFlags    = flags;
 }
 
@@ -739,6 +784,7 @@
                                          const SkColor colors[],
                                          const SkScalar pos[], int colorCount,
                                          SkShader::TileMode mode,
+                                         SkUnitMapper* mapper,
                                          uint32_t flags,
                                          const SkMatrix* localMatrix) {
     if (NULL == pts || NULL == colors || colorCount < 1) {
@@ -747,7 +793,7 @@
     EXPAND_1_COLOR(colorCount);
 
     SkGradientShaderBase::Descriptor desc;
-    desc_init(&desc, colors, pos, colorCount, mode, flags);
+    desc_init(&desc, colors, pos, colorCount, mode, mapper, flags);
     return SkNEW_ARGS(SkLinearGradient, (pts, desc, localMatrix));
 }
 
@@ -755,6 +801,7 @@
                                          const SkColor colors[],
                                          const SkScalar pos[], int colorCount,
                                          SkShader::TileMode mode,
+                                         SkUnitMapper* mapper,
                                          uint32_t flags,
                                          const SkMatrix* localMatrix) {
     if (radius <= 0 || NULL == colors || colorCount < 1) {
@@ -763,7 +810,7 @@
     EXPAND_1_COLOR(colorCount);
 
     SkGradientShaderBase::Descriptor desc;
-    desc_init(&desc, colors, pos, colorCount, mode, flags);
+    desc_init(&desc, colors, pos, colorCount, mode, mapper, flags);
     return SkNEW_ARGS(SkRadialGradient, (center, radius, desc, localMatrix));
 }
 
@@ -775,6 +822,7 @@
                                                  const SkScalar pos[],
                                                  int colorCount,
                                                  SkShader::TileMode mode,
+                                                 SkUnitMapper* mapper,
                                                  uint32_t flags,
                                                  const SkMatrix* localMatrix) {
     if (startRadius < 0 || endRadius < 0 || NULL == colors || colorCount < 1) {
@@ -783,7 +831,7 @@
     EXPAND_1_COLOR(colorCount);
 
     SkGradientShaderBase::Descriptor desc;
-    desc_init(&desc, colors, pos, colorCount, mode, flags);
+    desc_init(&desc, colors, pos, colorCount, mode, mapper, flags);
     return SkNEW_ARGS(SkTwoPointRadialGradient,
                       (start, startRadius, end, endRadius, desc, localMatrix));
 }
@@ -796,6 +844,7 @@
                                                   const SkScalar pos[],
                                                   int colorCount,
                                                   SkShader::TileMode mode,
+                                                  SkUnitMapper* mapper,
                                                   uint32_t flags,
                                                   const SkMatrix* localMatrix) {
     if (startRadius < 0 || endRadius < 0 || NULL == colors || colorCount < 1) {
@@ -812,7 +861,7 @@
     SkGradientShaderBase::Descriptor desc;
 
     if (!flipGradient) {
-        desc_init(&desc, colors, pos, colorCount, mode, flags);
+        desc_init(&desc, colors, pos, colorCount, mode, mapper, flags);
         return SkNEW_ARGS(SkTwoPointConicalGradient,
                           (start, startRadius, end, endRadius, flipGradient, desc, localMatrix));
     } else {
@@ -826,9 +875,9 @@
             for (int i = 0; i < colorCount; ++i) {
                 posNew[i] = 1 - pos[colorCount - i - 1];
             }
-            desc_init(&desc, colorsNew.get(), posNew.get(), colorCount, mode, flags);
+            desc_init(&desc, colorsNew.get(), posNew.get(), colorCount, mode, mapper, flags);
         } else {
-            desc_init(&desc, colorsNew.get(), NULL, colorCount, mode, flags);
+            desc_init(&desc, colorsNew.get(), NULL, colorCount, mode, mapper, flags);
         }
 
         return SkNEW_ARGS(SkTwoPointConicalGradient,
@@ -839,7 +888,7 @@
 SkShader* SkGradientShader::CreateSweep(SkScalar cx, SkScalar cy,
                                         const SkColor colors[],
                                         const SkScalar pos[],
-                                        int colorCount,
+                                        int colorCount, SkUnitMapper* mapper,
                                         uint32_t flags,
                                         const SkMatrix* localMatrix) {
     if (NULL == colors || colorCount < 1) {
@@ -848,7 +897,7 @@
     EXPAND_1_COLOR(colorCount);
 
     SkGradientShaderBase::Descriptor desc;
-    desc_init(&desc, colors, pos, colorCount, SkShader::kClamp_TileMode, flags);
+    desc_init(&desc, colors, pos, colorCount, SkShader::kClamp_TileMode, mapper, flags);
     return SkNEW_ARGS(SkSweepGradient, (cx, cy, desc, localMatrix));
 }