9efd9a048a
us to perform quick-rejects when drawing objects with shadows (esp. text). WebKit draws shadows w/ a looper (fg and shadow) and a maskfilter on the shadow layer. git-svn-id: http://skia.googlecode.com/svn/trunk@3103 2bbb7eff-a529-9590-31e7-b0007b416f81
71 lines
2.6 KiB
C++
71 lines
2.6 KiB
C++
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/*
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* Copyright 2011 The Android Open Source Project
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*
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* Use of this source code is governed by a BSD-style license that can be
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* found in the LICENSE file.
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*/
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#ifndef SkDrawLooper_DEFINED
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#define SkDrawLooper_DEFINED
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#include "SkFlattenable.h"
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class SkCanvas;
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class SkPaint;
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/** \class SkDrawLooper
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Subclasses of SkDrawLooper can be attached to a SkPaint. Where they are,
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and something is drawn to a canvas with that paint, the looper subclass will
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be called, allowing it to modify the canvas and/or paint for that draw call.
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More than that, via the next() method, the looper can modify the draw to be
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invoked multiple times (hence the name loop-er), allow it to perform effects
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like shadows or frame/fills, that require more than one pass.
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*/
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class SK_API SkDrawLooper : public SkFlattenable {
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public:
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/**
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* Called right before something is being drawn. This will be followed by
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* calls to next() until next() returns false.
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*/
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virtual void init(SkCanvas*) = 0;
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/**
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* Called in a loop (after init()). Each time true is returned, the object
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* is drawn (possibly with a modified canvas and/or paint). When false is
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* finally returned, drawing for the object stops.
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*
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* On each call, the paint will be in its original state, but the canvas
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* will be as it was following the previous call to next() or init().
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*
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* The implementation must ensure that, when next() finally returns false,
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* that the canvas has been restored to the state it was initially, before
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* init() was first called.
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*/
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virtual bool next(SkCanvas*, SkPaint* paint) = 0;
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/**
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* The fast bounds functions are used to enable the paint to be culled early
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* in the drawing pipeline. If a subclass can support this feature it must
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* return true for the canComputeFastBounds() function. If that function
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* returns false then computeFastBounds behavior is undefined otherwise it
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* is expected to have the following behavior. Given the parent paint and
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* the parent's bounding rect the subclass must fill in and return the
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* storage rect, where the storage rect is with the union of the src rect
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* and the looper's bounding rect.
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*/
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virtual bool canComputeFastBounds(const SkPaint& paint);
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virtual void computeFastBounds(const SkPaint& paint,
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const SkRect& src, SkRect* dst);
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protected:
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SkDrawLooper() {}
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SkDrawLooper(SkFlattenableReadBuffer& buffer) : INHERITED(buffer) {}
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private:
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typedef SkFlattenable INHERITED;
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};
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#endif
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