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 73 matching lines @@
 }
 
 // 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(
     HDC screen_dc,
     int width,
     int height,
-    bool is_opaque,
+    int flags,
     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)) {
     width = 1;
     height = 1;
   }
 
   BITMAPINFOHEADER hdr = {0};
@@ skipping 13 matching lines @@
   HBITMAP hbitmap = CreateDIBSection(screen_dc,
                                      reinterpret_cast<BITMAPINFO*>(&hdr), 0,
                                      &data,
                                      shared_section, 0);
   if (!hbitmap) {
     return NULL;
   }
 
   bitmap.setConfig(SkBitmap::kARGB_8888_Config, width, height);
   bitmap.setPixels(data);
-  bitmap.setIsOpaque(is_opaque);
+  bitmap.setIsOpaque(flags & FLAGS_OPAQUE);
 
   // If we were given data, then don't clobber it!
   if (!shared_section) {
-    if (is_opaque) {
+    if (flags & FLAGS_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);
+      if (flags & FLAGS_INITIALIZED)
+        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,
                                                    int height,
-                                                   bool is_opaque,
+                                                   int flags,
                                                    HANDLE shared_section) {
   HDC screen_dc = GetDC(NULL);
   BitmapPlatformDevice* device = BitmapPlatformDevice::create(
-      screen_dc, width, height, is_opaque, shared_section);
+      screen_dc, width, height, flags, shared_section);
   ReleaseDC(NULL, screen_dc);
   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),
@@ skipping 84 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);
+  return BitmapPlatformDevice::create(width, height,
+                                      GetDefaultFlags(isOpaque),
+                                      NULL);
 }
 
 }  // namespace skia