Srcover for sprite blitters.

src/core/SkBlitter_Sprite.cpp

Index: src/core/SkBlitter_Sprite.cpp
diff --git a/src/core/SkBlitter_Sprite.cpp b/src/core/SkBlitter_Sprite.cpp
index c0b7430d22f4d950661fe530db6fe60fde6d0b98..a679cf704d16571b2863f844c0155e547f8d4b5d 100644
--- a/src/core/SkBlitter_Sprite.cpp
+++ b/src/core/SkBlitter_Sprite.cpp
@@ -5,6 +5,7 @@
  * found in the LICENSE file.
  */
 
+#include "SkOpts.h"
 #include "SkSmallAllocator.h"
 #include "SkSpriteBlitter.h"
 
@@ -99,6 +100,60 @@ public:
     typedef SkSpriteBlitter INHERITED;
 };
 
+class SkSpriteBlitter_SrcOver : public SkSpriteBlitter {
+public:
+    static bool Supports(const SkPixmap& dst, const SkPixmap& src, const SkPaint& paint) {
+        if (dst.colorType() != src.colorType() || dst.colorType() != kN32_SkColorType) {
+            return false;
+        }
+        if (dst.info().profileType() != src.info().profileType()

[msarett, 2016/05/20 15:46:58]

Can you check the gDefaultProfileIsSRGB flag directly here?  Instead of relying
on SkCodec to check it for you?

I'd like to remove that logic from SkCodec.

+            || dst.info().profileType() != kSRGB_SkColorProfileType) {
+            return false;
+        }
+        if (paint.getMaskFilter() || paint.getColorFilter() || paint.getImageFilter()) {
+            return false;
+        }
+        if (0xFF != paint.getAlpha()) {
+            return false;
+        }
+        SkXfermode::Mode mode;
+        if (!SkXfermode::AsMode(paint.getXfermode(), &mode)) {
+            return false;
+        }
+        return SkXfermode::kSrcOver_Mode == mode;
+    }
+
+    SkSpriteBlitter_SrcOver(const SkPixmap& src)  : INHERITED(src) {}
+
+    void setup(const SkPixmap& dst, int left, int top, const SkPaint& paint) override {
+        SkASSERT(Supports(dst, fSource, paint));
+        this->INHERITED::setup(dst, left, top, paint);
+        SkXfermode::Mode mode;
+        if (!SkXfermode::AsMode(paint.getXfermode(), &mode)) {
+            SkFAIL("Should never happen.");
+        }
+        SkASSERT(SkXfermode::kSrcOver_Mode == mode);
+    }
+
+    void blitRect(int x, int y, int width, int height) override {
+        SkASSERT(fDst.colorType() == fSource.colorType());
+        SkASSERT(fDst.info().profileType() == fSource.info().profileType());
+        SkASSERT(width > 0 && height > 0);
+
+        uint32_t* dst = fDst.writable_addr32(x, y);
+        const uint32_t* src = fSource.addr32(x - fLeft, y - fTop);
+        const int dstRB = fDst.rowBytesAsPixels();
+        const int srcRB = fSource.rowBytesAsPixels();
+
+        while (height --> 0) {
+            SkOpts::srcover_srgb_srgb(dst, src, width, width);
+            dst += dstRB;
+            src += srcRB;
+        }
+    }
+
+    typedef SkSpriteBlitter INHERITED;
+};
 
 // returning null means the caller will call SkBlitter::Choose() and
 // have wrapped the source bitmap inside a shader
@@ -115,10 +170,12 @@ SkBlitter* SkBlitter::ChooseSprite(const SkPixmap& dst, const SkPaint& paint,
     */
     SkASSERT(allocator != nullptr);
 
-    SkSpriteBlitter* blitter;
+    SkSpriteBlitter* blitter = nullptr;
 
     if (SkSpriteBlitter_memcpy::Supports(dst, source, paint)) {
         blitter = allocator->createT<SkSpriteBlitter_memcpy>(source);
+    } else if (SkSpriteBlitter_SrcOver::Supports(dst, source, paint)) {
+        blitter = allocator->createT<SkSpriteBlitter_SrcOver>(source);
     } else {
         switch (dst.colorType()) {
             case kRGB_565_SkColorType:
@@ -135,7 +192,6 @@ SkBlitter* SkBlitter::ChooseSprite(const SkPixmap& dst, const SkPaint& paint,
                 blitter = SkSpriteBlitter::ChooseF16(source, paint, allocator);
                 break;
             default:
-                blitter = nullptr;
                 break;
         }
     }