Optionally clear PlatformCanvas instances.

skia/ext/bitmap_platform_device_win.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include <windows.h>
 #include <psapi.h>
 
 #include "skia/ext/bitmap_platform_device_win.h"
 
 #include "skia/ext/bitmap_platform_device_data.h"
@@ skipping 69 matching lines @@
 
   // Transform.
   LoadTransformToDC(hdc_, transform_);
   LoadClippingRegionToDC(hdc_, clip_region_, transform_);
 }
 
 // We use this static factory function instead of the regular constructor so
 // that we can create the pixel data before calling the constructor. This is
 // required so that we can call the base class' constructor with the pixel
 // data.
-BitmapPlatformDevice* BitmapPlatformDevice::create(
+BitmapPlatformDevice* BitmapPlatformDevice::Create(
     HDC screen_dc,
     int width,
     int height,
     bool is_opaque,
     HANDLE shared_section) {
   SkBitmap bitmap;
 
   // CreateDIBSection appears to get unhappy if we create an empty bitmap, so
   // just create a minimal bitmap
   if ((width == 0) || (height == 0)) {
@@ skipping 21 matching lines @@
                                      shared_section, 0);
   if (!hbitmap) {
     return NULL;
   }
 
   bitmap.setConfig(SkBitmap::kARGB_8888_Config, width, height);
   bitmap.setPixels(data);
   bitmap.setIsOpaque(is_opaque);
 
   // If we were given data, then don't clobber it!
   if (!shared_section) {

[msw, 2012/03/16 07:13:22]

nit: combine nested ifs, drop braces, put the whole block in the #ifndef.

[Jeff Timanus, 2012/03/16 15:52:42]

Done.

     if (is_opaque) {
 #ifndef NDEBUG
       // To aid in finding bugs, we set the background color to something
       // obviously wrong so it will be noticable when it is not cleared
       bitmap.eraseARGB(255, 0, 255, 128);  // bright bluish green
 #endif
-    } else {
-      bitmap.eraseARGB(0, 0, 0, 0);
     }
   }
 
   // The device object will take ownership of the HBITMAP. The initial refcount
   // of the data object will be 1, which is what the constructor expects.
   return new BitmapPlatformDevice(new BitmapPlatformDeviceData(hbitmap),
                                   bitmap);
 }
 
 // static
-BitmapPlatformDevice* BitmapPlatformDevice::create(int width,
+BitmapPlatformDevice* BitmapPlatformDevice::Create(int width,
                                                    int height,
                                                    bool is_opaque,
                                                    HANDLE shared_section) {
   HDC screen_dc = GetDC(NULL);
-  BitmapPlatformDevice* device = BitmapPlatformDevice::create(
+  BitmapPlatformDevice* device = BitmapPlatformDevice::Create(
       screen_dc, width, height, is_opaque, shared_section);
   ReleaseDC(NULL, screen_dc);
   return device;
 }
 
+// static
+BitmapPlatformDevice* BitmapPlatformDevice::Create(int width, int height,
+                                                   bool is_opaque) {
+  return Create(width, height, is_opaque, NULL);
+}
+
+// static
+BitmapPlatformDevice* BitmapPlatformDevice::CreateAndClear(int width,
+                                                           int height,
+                                                           bool is_opaque) {
+  BitmapPlatformDevice* device = BitmapPlatformDevice::Create(width, height,
+                                                              is_opaque);
+  if (!is_opaque)
+    device->accessBitmap(true).eraseARGB(0, 0, 0, 0);
+  return device;
+}
+
 // The device will own the HBITMAP, which corresponds to also owning the pixel
 // data. Therefore, we do not transfer ownership to the SkDevice's bitmap.
 BitmapPlatformDevice::BitmapPlatformDevice(
     BitmapPlatformDeviceData* data,
     const SkBitmap& bitmap)
     : SkDevice(bitmap),
       data_(data) {
   // The data object is already ref'ed for us by create().
   SkDEBUGCODE(begin_paint_count_ = 0);
   SetPlatformDevice(this, this);
@@ skipping 80 matching lines @@
   // operation has occurred on our DC.
   if (data_->IsBitmapDCCreated())
     GdiFlush();
   return *bitmap;
 }
 
 SkDevice* BitmapPlatformDevice::onCreateCompatibleDevice(
     SkBitmap::Config config, int width, int height, bool isOpaque,
     Usage /*usage*/) {
   SkASSERT(config == SkBitmap::kARGB_8888_Config);
-  return BitmapPlatformDevice::create(width, height, isOpaque, NULL);
+  SkDevice* bitmap_device = BitmapPlatformDevice::CreateAndClear(width, height,
+                                                                 isOpaque);
+  return bitmap_device;
 }
 
 }  // namespace skia