Optionally clear PlatformCanvas instances.

skia/ext/bitmap_platform_device_linux.cc

Index: skia/ext/bitmap_platform_device_linux.cc
===================================================================
--- skia/ext/bitmap_platform_device_linux.cc	(revision 123041)
+++ skia/ext/bitmap_platform_device_linux.cc	(working copy)
@@ -81,13 +81,13 @@
 // required so that we can call the base class' constructor with the pixel
 // data.
 BitmapPlatformDevice* BitmapPlatformDevice::Create(int width, int height,
-                                                   bool is_opaque,
+                                                   int flags,
                                                    cairo_surface_t* surface) {
   SkBitmap bitmap;
   bitmap.setConfig(SkBitmap::kARGB_8888_Config, width, height,
                    cairo_image_surface_get_stride(surface));
   bitmap.setPixels(cairo_image_surface_get_data(surface));
-  bitmap.setIsOpaque(is_opaque);
+  bitmap.setIsOpaque(flags & FLAGS_OPAQUE);
 
   // The device object will take ownership of the graphics context.
   return new BitmapPlatformDevice
@@ -95,15 +95,15 @@
 }
 
 BitmapPlatformDevice* BitmapPlatformDevice::Create(int width, int height,
-                                                   bool is_opaque) {
+                                                   int flags) {
   // This initializes the bitmap to all zeros.
   cairo_surface_t* surface = cairo_image_surface_create(CAIRO_FORMAT_ARGB32,
                                                         width, height);
 
-  BitmapPlatformDevice* device = Create(width, height, is_opaque, surface);
+  BitmapPlatformDevice* device = Create(width, height, flags, surface);
 
 #ifndef NDEBUG
-  if (is_opaque)  // Fill with bright bluish green
+  if (flags & FLAGS_OPAQUE)  // Fill with bright bluish green
     device->eraseColor(SkColorSetARGB(255, 0, 255, 128));
 #endif
 
@@ -111,13 +111,12 @@
 }
 
 BitmapPlatformDevice* BitmapPlatformDevice::Create(int width, int height,
-                                                   bool is_opaque,
-                                                   uint8_t* data) {
+                                                   int flags, uint8_t* data) {
   cairo_surface_t* surface = cairo_image_surface_create_for_data(
       data, CAIRO_FORMAT_ARGB32, width, height,
       cairo_format_stride_for_width(CAIRO_FORMAT_ARGB32, width));
 
-  return Create(width, height, is_opaque, surface);
+  return Create(width, height, flags, surface);
 }
 
 // The device will own the bitmap, which corresponds to also owning the pixel
@@ -137,7 +136,7 @@
     SkBitmap::Config config, int width, int height, bool isOpaque,
     Usage /*usage*/) {
   SkASSERT(config == SkBitmap::kARGB_8888_Config);
-  return BitmapPlatformDevice::Create(width, height, isOpaque);
+  return BitmapPlatformDevice::Create(width, height, GetDefaultFlags(isOpaque));

[Jeff Timanus, 2012/02/23 22:14:10]

The various BitmapPlatformDevice::onCreateCompatibleDevice calls could clear the
buffer explicitly.  The linux port could skip the clear, to prevent the double
clear.

 }
 
 cairo_t* BitmapPlatformDevice::BeginPlatformPaint() {