We assume that each SkDevice is our custom PlatformDevice. This assumption is not valid when usin...

skia/ext/platform_canvas.cc

 // Copyright (c) 2006-2008 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/platform_canvas.h"
 
 #include "skia/ext/bitmap_platform_device.h"
+#include "third_party/skia/include/core/SkMetaData.h"
 #include "third_party/skia/include/core/SkTypes.h"
 
 namespace {
+static const char* kPlatformDeviceIdentifier = "CrPlatformDevice";

[Jeff Timanus, 2011/05/04 21:22:47]

Style guide nit/question.  Does static have any meaning in an unnamed
named-space in a .cc translation unit?

+
 skia::PlatformDevice* GetTopPlatformDevice(const SkCanvas* canvas) {
-  // All of our devices should be our special PlatformDevice.
   SkCanvas::LayerIter iter(const_cast<SkCanvas*>(canvas), false);
-  return static_cast<skia::PlatformDevice*>(iter.device());
+  SkDevice* device = iter.device();
+  // Check if this device is our custom PlatformDevice.
+  // The custom devices are tagged with meta-data named
+  // kPlatformDeviceIdentifier.
+  SkMetaData& meta_data = device->getMetaData();
+  return meta_data.findBool(kPlatformDeviceIdentifier) ?
+      static_cast<skia::PlatformDevice*>(device) : NULL;
 }
 }
 
 namespace skia {
 
 PlatformCanvas::PlatformCanvas() {
   setDeviceFactory(SkNEW(BitmapPlatformDeviceFactory))->unref();
 }
 
 PlatformCanvas::PlatformCanvas(SkDeviceFactory* factory) : SkCanvas(factory) {
 }
 
 SkDevice* PlatformCanvas::setBitmapDevice(const SkBitmap&) {
   SkASSERT(false);  // Should not be called.
   return NULL;
 }
 
 PlatformDevice& PlatformCanvas::getTopPlatformDevice() const {
   return *GetTopPlatformDevice(this);
 }
 
 // static
 size_t PlatformCanvas::StrideForWidth(unsigned width) {
   return 4 * width;
 }
 
-bool PlatformCanvas::initializeWithDevice(SkDevice* device) {
+bool PlatformCanvas::initializeWithDevice(PlatformDevice* device) {
   if (!device)
     return false;
 
+  // Set meta-data on the device indicating that this device is our custom
+  // platform device.
+  SkMetaData& meta_data = device->getMetaData();
+  meta_data.setBool(kPlatformDeviceIdentifier, true);
+
   setDevice(device);
   device->unref();  // Was created with refcount 1, and setDevice also refs.
   return true;
 }
 
 SkCanvas* CreateBitmapCanvas(int width, int height, bool is_opaque) {
   return new PlatformCanvas(width, height, is_opaque);
 }
 
 bool SupportsPlatformPaint(const SkCanvas* canvas) {
-  // TODO(alokp): Rename PlatformDevice::IsNativeFontRenderingAllowed after
-  // removing these calls from WebKit.
-  return GetTopPlatformDevice(canvas)->IsNativeFontRenderingAllowed();
+  skia::PlatformDevice* device = GetTopPlatformDevice(canvas);
+  return device ? device->IsNativeFontRenderingAllowed() : false;
 }
 
 PlatformDevice::PlatformSurface BeginPlatformPaint(SkCanvas* canvas) {
   return GetTopPlatformDevice(canvas)->BeginPlatformPaint();
 }
 
 void EndPlatformPaint(SkCanvas* canvas) {
   GetTopPlatformDevice(canvas)->EndPlatformPaint();
 }
 
 }  // namespace skia