store SkAlphaType inside SkBitmap, on road to support unpremul

src/core/SkBitmapDevice.cpp

 /*
  * Copyright 2013 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkBitmapDevice.h"
 #include "SkConfig8888.h"
 #include "SkDraw.h"
 #include "SkRasterClip.h"
 #include "SkShader.h"
 
 SK_DEFINE_INST_COUNT(SkBitmapDevice)
 
 #define CHECK_FOR_NODRAW_ANNOTATION(paint) \
     do { if (paint.isNoDrawAnnotation()) { return; } } while (0)
 
 SkBitmapDevice::SkBitmapDevice(const SkBitmap& bitmap)
     : fBitmap(bitmap) {
     SkASSERT(SkBitmap::kARGB_4444_Config != bitmap.config());
 }
 
 SkBitmapDevice::SkBitmapDevice(const SkBitmap& bitmap, const SkDeviceProperties& deviceProperties)
     : SkBaseDevice(deviceProperties)
     , fBitmap(bitmap) {
 }
 
 SkBitmapDevice::SkBitmapDevice(SkBitmap::Config config, int width, int height, bool isOpaque) {
-    fBitmap.setConfig(config, width, height);
+    fBitmap.setConfig(config, width, height, 0, isOpaque ?

[scroggo, 2013/10/18 19:32:40]

Should we update the parameter? Maybe in the future?

+                      kOpaque_SkAlphaType : kPremul_SkAlphaType);
     fBitmap.allocPixels();
-    fBitmap.setIsOpaque(isOpaque);
     if (!isOpaque) {
         fBitmap.eraseColor(SK_ColorTRANSPARENT);
     }
 }
 
 SkBitmapDevice::SkBitmapDevice(SkBitmap::Config config, int width, int height, bool isOpaque,
                                const SkDeviceProperties& deviceProperties)
     : SkBaseDevice(deviceProperties) {
 
-    fBitmap.setConfig(config, width, height);
+    fBitmap.setConfig(config, width, height, 0, isOpaque ?
+                      kOpaque_SkAlphaType : kPremul_SkAlphaType);
     fBitmap.allocPixels();
-    fBitmap.setIsOpaque(isOpaque);
     if (!isOpaque) {
         fBitmap.eraseColor(SK_ColorTRANSPARENT);
     }
 }
 
 SkBitmapDevice::~SkBitmapDevice() {
 }
 
 void SkBitmapDevice::replaceBitmapBackendForRasterSurface(const SkBitmap& bm) {
     SkASSERT(bm.width() == fBitmap.width());
@@ skipping 345 matching lines @@
         paint.getStyle() != SkPaint::kFill_Style ||
         !SkXfermode::IsMode(paint.getXfermode(), SkXfermode::kSrcOver_Mode)) {
         // turn off lcd
         flags->fFlags = paint.getFlags() & ~SkPaint::kLCDRenderText_Flag;
         flags->fHinting = paint.getHinting();
         return true;
     }
     // we're cool with the paint as is
     return false;
 }