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Diffstat (limited to 'include/core/SkDrawable.h')
-rw-r--r-- | include/core/SkDrawable.h | 76 |
1 files changed, 76 insertions, 0 deletions
diff --git a/include/core/SkDrawable.h b/include/core/SkDrawable.h new file mode 100644 index 0000000000..15bb0bbe0f --- /dev/null +++ b/include/core/SkDrawable.h @@ -0,0 +1,76 @@ +/* + * Copyright 2014 Google Inc. + * + * Use of this source code is governed by a BSD-style license that can be + * found in the LICENSE file. + */ + +#ifndef SkDrawable_DEFINED +#define SkDrawable_DEFINED + +#include "SkRefCnt.h" + +class SkCanvas; +class SkPicture; +struct SkRect; + +/** + * Base-class for objects that draw into SkCanvas. + * + * The object has a generation ID, which is guaranteed to be unique across all drawables. To + * allow for clients of the drawable that may want to cache the results, the drawable must + * change its generation ID whenever its internal state changes such that it will draw differently. + */ +class SkDrawable : public SkRefCnt { +public: + SkDrawable(); + + /** + * Draws into the specified content. The drawing sequence will be balanced upon return + * (i.e. the saveLevel() on the canvas will match what it was when draw() was called, + * and the current matrix and clip settings will not be changed. + */ + void draw(SkCanvas*); + + SkPicture* newPictureSnapshot(); + + /** + * Return a unique value for this instance. If two calls to this return the same value, + * it is presumed that calling the draw() method will render the same thing as well. + * + * Subclasses that change their state should call notifyDrawingChanged() to ensure that + * a new value will be returned the next time it is called. + */ + uint32_t getGenerationID(); + + /** + * Return the (conservative) bounds of what the drawable will draw. If the drawable can + * change what it draws (e.g. animation or in response to some external change), then this + * must return a bounds that is always valid for all possible states. + */ + SkRect getBounds(); + + /** + * Calling this invalidates the previous generation ID, and causes a new one to be computed + * the next time getGenerationID() is called. Typically this is called by the object itself, + * in response to its internal state changing. + */ + void notifyDrawingChanged(); + +protected: + virtual SkRect onGetBounds() = 0; + virtual void onDraw(SkCanvas*) = 0; + + /** + * Default implementation calls onDraw() with a canvas that records into a picture. Subclasses + * may override if they have a more efficient way to return a picture for the current state + * of their drawable. Note: this picture must draw the same as what would be drawn from + * onDraw(). + */ + virtual SkPicture* onNewPictureSnapshot(); + +private: + int32_t fGenerationID; +}; + +#endif |