store SkAlphaType inside SkBitmap, on road to support unpremul

src/core/SkBitmap.cpp

Index: src/core/SkBitmap.cpp
diff --git a/src/core/SkBitmap.cpp b/src/core/SkBitmap.cpp
index 128726cb63d9198477afd698e377c6ee02cef6ed..0f30945ab4b5dd225d25c1f723905f4c82a07def 100644
--- a/src/core/SkBitmap.cpp
+++ b/src/core/SkBitmap.cpp
@@ -266,33 +266,88 @@ void SkBitmap::getBounds(SkIRect* bounds) const {
 
 ///////////////////////////////////////////////////////////////////////////////
 
-void SkBitmap::setConfig(Config c, int width, int height, size_t rowBytes) {
-    this->freePixels();
-
+bool SkBitmap::setConfig(Config config, int width, int height, size_t rowBytes,
+                         SkAlphaType alphaType) {
     if ((width | height) < 0) {
-        goto err;
+        goto ERROR;
     }
-
     if (rowBytes == 0) {
-        rowBytes = SkBitmap::ComputeRowBytes(c, width);
-        if (0 == rowBytes && kNo_Config != c) {
-            goto err;
+        rowBytes = SkBitmap::ComputeRowBytes(config, width);
+        if (0 == rowBytes && kNo_Config != config) {
+            goto ERROR;
         }
     }
 
-    fConfig     = SkToU8(c);
+    // check for legal/supported config+alphaType combinations
+    //
+    switch (config) {
+        case kNo_Config:
+            alphaType = kIgnore_SkAlphaType;    // canonicalize
+            break;
+        case kA1_Config:
+        case kA8_Config:
+            if (kUnpremul_SkAlphaType == alphaType) {
+                alphaType = kPremul_SkAlphaType;
+            }
+            // fall-through
+        case kIndex8_Config:
+        case kARGB_4444_Config:
+        case kARGB_8888_Config:
+            if (kIgnore_SkAlphaType == alphaType) {
+                goto ERROR;   // not supported yet
+            }
+            break;
+        case kRGB_565_Config:
+            alphaType = kOpaque_SkAlphaType;    // canonicalize
+            break;
+    }
+
+    this->freePixels();
+
+    fConfig     = SkToU8(config);
+    fAlphaType  = SkToU8(alphaType);
     fWidth      = width;
     fHeight     = height;
     fRowBytes   = SkToU32(rowBytes);
 
-    fBytesPerPixel = (uint8_t)ComputeBytesPerPixel(c);
+    fBytesPerPixel = (uint8_t)ComputeBytesPerPixel(config);
 
     SkDEBUGCODE(this->validate();)
-    return;
+    return true;
 
     // if we got here, we had an error, so we reset the bitmap to empty
-err:
+ERROR:
     this->reset();
+    return false;
+}
+
+void SkBitmap::setAlphaType(SkAlphaType alphaType) {
+    // check for legal/supported config+alphaType combinations
+    //
+    switch (this->config()) {
+        case kNo_Config:
+            alphaType = kIgnore_SkAlphaType;    // canonicalize
+            break;
+        case kA1_Config:
+        case kA8_Config:
+            if (kUnpremul_SkAlphaType == alphaType) {
+                alphaType = kPremul_SkAlphaType;
+            }
+            // fall-through
+        case kIndex8_Config:
+        case kARGB_4444_Config:
+        case kARGB_8888_Config:
+            if (kIgnore_SkAlphaType == alphaType) {
+                SkDEBUGFAIL("bad alphaType for existing config");
+                return;
+            }
+            break;
+        case kRGB_565_Config:
+            alphaType = kOpaque_SkAlphaType;    // canonicalize
+            break;
+    }
+    
+    fAlphaType = SkToU8(alphaType);
 }
 
 void SkBitmap::updatePixelsFromRef() const {
@@ -525,6 +580,9 @@ void SkBitmap::setImmutable() {
 }
 
 bool SkBitmap::isOpaque() const {
+    return kOpaque_SkAlphaType == fAlphaType ||
+           kIgnore_SkAlphaType == fAlphaType;
+#if 0
     switch (fConfig) {
         case kNo_Config:
             return true;
@@ -555,8 +613,10 @@ bool SkBitmap::isOpaque() const {
             SkDEBUGFAIL("unknown bitmap config pased to isOpaque");
             return false;
     }
+#endif
 }
 
+#if 0
 void SkBitmap::setIsOpaque(bool isOpaque) {
     /*  we record this regardless of fConfig, though it is ignored in
         isOpaque() for configs that can't support per-pixel alpha.
@@ -567,6 +627,7 @@ void SkBitmap::setIsOpaque(bool isOpaque) {
         fFlags &= ~kImageIsOpaque_Flag;
     }
 }
+#endif
 
 bool SkBitmap::isVolatile() const {
     return (fFlags & kImageIsVolatile_Flag) != 0;
@@ -962,9 +1023,10 @@ bool SkBitmap::extractSubset(SkBitmap* result, const SkIRect& subset) const {
         SkPixelRef* pixelRef = fPixelRef->deepCopy(this->config(), &subset);
         if (pixelRef != NULL) {
             SkBitmap dst;
-            dst.setConfig(this->config(), subset.width(), subset.height());
+            dst.setConfig(this->config(), subset.width(), subset.height(), 0,
+                          this->isOpaque() ?
+                          kOpaque_SkAlphaType : kPremul_SkAlphaType);
             dst.setIsVolatile(this->isVolatile());
-            dst.setIsOpaque(this->isOpaque());
             dst.setPixelRef(pixelRef)->unref();
             SkDEBUGCODE(dst.validate());
             result->swap(dst);
@@ -983,9 +1045,9 @@ bool SkBitmap::extractSubset(SkBitmap* result, const SkIRect& subset) const {
     }
 
     SkBitmap dst;
-    dst.setConfig(this->config(), r.width(), r.height(), this->rowBytes());
+    dst.setConfig(this->config(), r.width(), r.height(), this->rowBytes(),
+                  this->isOpaque() ? kOpaque_SkAlphaType : kPremul_SkAlphaType);
     dst.setIsVolatile(this->isVolatile());
-    dst.setIsOpaque(this->isOpaque());
 
     if (fPixelRef) {
         // share the pixelref with a custom offset
@@ -1135,7 +1197,8 @@ bool SkBitmap::copyTo(SkBitmap* dst, Config dstConfig, Allocator* alloc) const {
         canvas.drawBitmap(*src, 0, 0, &paint);
     }
 
-    tmpDst.setIsOpaque(src->isOpaque());
+    tmpDst.setAlphaType(src->isOpaque() ?
+                        kOpaque_SkAlphaType : kPremul_SkAlphaType);
 
     dst->swap(tmpDst);
     return true;
@@ -1608,8 +1671,9 @@ void SkBitmap::unflatten(SkFlattenableReadBuffer& buffer) {
     int rowBytes = buffer.readInt();
     int config = buffer.readInt();
 
-    this->setConfig((Config)config, width, height, rowBytes);
-    this->setIsOpaque(buffer.readBool());
+    bool isOpaque = buffer.readBool();
+    this->setConfig((Config)config, width, height, rowBytes,
+                    isOpaque ? kOpaque_SkAlphaType : kPremul_SkAlphaType);
 
     int reftype = buffer.readInt();
     switch (reftype) {