Hook up CSSPaintValue::image to CSS Paint API callback.

third_party/WebKit/Source/modules/csspaint/CSSPaintDefinition.h

 // Copyright 2016 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.
 
 #ifndef CSSPaintDefinition_h
 #define CSSPaintDefinition_h
 
 #include "bindings/core/v8/ScopedPersistent.h"
 #include "platform/geometry/IntSize.h"
 #include "platform/heap/Handle.h"
 #include <v8.h>
 
 namespace blink {
 
+class Image;
 class ScriptState;
 
+// Represents a javascript class registered on the PaintWorkletGlobalScope by
+// the author.
 class CSSPaintDefinition final : public GarbageCollectedFinalized<CSSPaintDefinition> {
 public:
     static CSSPaintDefinition* create(ScriptState*, v8::Local<v8::Function> constructor, v8::Local<v8::Function> paint);
     virtual ~CSSPaintDefinition();
 
+    // Invokes the javascript 'paint' callback on an instance of the javascript
+    // class. The size given will be the size of the PaintRenderingContext2D
+    // given to the callback.
+    //
+    // This may return a nullptr (representing an invalid image) if javascript
+    // throws an error.
+    PassRefPtr<Image> paint(const IntSize&);
+
+    v8::Local<v8::Object> paintInstance();
+    ScriptState* getScriptState() const { return m_scriptState.get(); }
+
     v8::Local<v8::Function> paintFunctionForTesting(v8::Isolate* isolate) { return m_paint.newLocal(isolate); }
 
     DEFINE_INLINE_TRACE() { };
 
 private:
     CSSPaintDefinition(ScriptState*, v8::Local<v8::Function> constructor, v8::Local<v8::Function> paint);
 
     RefPtr<ScriptState> m_scriptState;
 
     // This object keeps the constructor and paint functions alive. This object
     // needs to be destroyed to break a reference cycle between it and the
     // PaintWorkletGlobalScope.
     ScopedPersistent<v8::Function> m_constructor;
     ScopedPersistent<v8::Function> m_paint;
+
+    // At the moment there is only ever one instance of a paint class per type.
+    // This is a weak reference, CSSPaintImageGeneratorImpl holds a persistent
+    // reference which keeps it alive.
+    ScopedPersistent<v8::Object> m_instance;

[haraken, 2016/04/08 04:31:19]

I guess it's a bit nasty to add m_instance to both CSSPaintDefinition and
CSSPaintImageGeneratorImpl. Why can't we just make CSSPaintDefinition hold a
strong reference?

[ikilpatrick, 2016/04/08 18:43:21]

The initial thinking was when a CSSPaintValue was GC'd it would also clean up
the instance if nessecery. This is probably a bit premature, under memory
pressure we'd more likely kill the entire workletGlobalScope.

I've deleted the CSSPaintImageGeneratorImpl and made this persistent.

 };
 
 } // namespace blink
 
 #endif // CSSPaintDefinition_h