Extend SkImageGenerator to support natively generated GrTextures

src/core/SkImageCacherator.h

+/*
+ * Copyright 2015 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#ifndef SkImageCacherator_DEFINED
+#define SkImageCacherator_DEFINED
+
+#include "SkImageGenerator.h"
+
+class GrContext;
+class SkBitmap;
+
+class SkImageCacherator {
+public:
+    // Takes ownership of the generator
+    SkImageCacherator(SkImageGenerator* gen);

[scroggo, 2015/08/13 19:59:13]

Maybe this should be a factory, so we don't end up getting any calls to

new SkImageCacherator(nullptr)

?

[reed1, 2015/08/13 20:57:08]

Done.

+    ~SkImageCacherator();
+
+    const SkImageInfo& info() const { return fGenerator->getInfo(); }
+    SkImageGenerator* generator() const { return fGenerator; }
+
+    /**
+     *  On success (true), bitmap will point to the pixels for this generator. If this returns
+     *  false, the bitmap will be reset to empty.
+     *
+     *  The cached bitmap is valid until it goes out of scope.

[scroggo, 2015/08/13 19:59:13]

Are you saying the bitmap passed to this function is valid until it goes out of
scope, or until the SkImageCacherator goes out of scope? What happens if the
client passes one on the heap?

[reed1, 2015/08/13 20:57:08]

Fixed.

+     */
+    bool lockAsBitmap(SkBitmap*);
+
+    /**
+     *  Returns a ref() on the texture produced by this generator. The caller must call unref()
+     *  when it is done. Will return NULL on failure.

[scroggo, 2015/08/13 19:59:13]

nullptr?

[reed1, 2015/08/13 20:57:08]

Hmmm, I'm not sure that distinction is important in a comment, but I hadn't
really considered it.

+     *
+     *  The cached texture is valid until it is unref'd.
+     */
+    GrTexture* lockAsTexture(GrContext*, SkImageUsageType);
+
+private:
+    bool tryLockAsBitmap(SkBitmap*);
+    GrTexture* tryLockAsTexture(GrContext*, SkImageUsageType);
+
+    SkImageGenerator* fGenerator;
+};
+
+#endif