Optionally clear PlatformCanvas instances.

skia/ext/bitmap_platform_device_linux.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 "skia/ext/bitmap_platform_device_linux.h"
 
 #include "skia/ext/bitmap_platform_device_data.h"
 
 #if defined(OS_OPENBSD)
 #include <cairo.h>
@@ skipping 63 matching lines @@
 
   LoadClipToContext(bitmap_context_, clip_region_);
   LoadMatrixToContext(bitmap_context_, 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(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
       (bitmap, new BitmapPlatformDeviceData(surface));
 }
 
 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
 
   return device;
 }
 
 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
 // data. Therefore, we do not transfer ownership to the SkDevice's bitmap.
 BitmapPlatformDevice::BitmapPlatformDevice(
     const SkBitmap& bitmap,
     BitmapPlatformDeviceData* data)
     : SkDevice(bitmap),
       data_(data) {
   SetPlatformDevice(this, this);
 }
 
 BitmapPlatformDevice::~BitmapPlatformDevice() {
 }
 
 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);
+  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() {
   data_->LoadConfig();
   cairo_t* cairo = data_->bitmap_context();
   cairo_surface_t* surface = cairo_get_target(cairo);
   // Tell cairo to flush anything it has pending.
   cairo_surface_flush(surface);
   // Tell Cairo that we (probably) modified (actually, will modify) its pixel
   // buffer directly.
   cairo_surface_mark_dirty(surface);
   return cairo;
 }
 
 void BitmapPlatformDevice::DrawToNativeContext(
     PlatformSurface surface, int x, int y, const PlatformRect* src_rect) {
   // Should never be called on Linux.
   SkASSERT(false);
 }
 
 void BitmapPlatformDevice::setMatrixClip(const SkMatrix& transform,
                                          const SkRegion& region,
                                          const SkClipStack&) {
   data_->SetMatrixClip(transform, region);
 }
 
 }  // namespace skia