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- /*
- * Copyright 2011 The Android Open Source Project
- *
- * Use of this source code is governed by a BSD-style license that can be
- * found in the LICENSE file.
- */
- #ifndef SkDrawLooper_DEFINED
- #define SkDrawLooper_DEFINED
- #include "include/core/SkBlurTypes.h"
- #include "include/core/SkColor.h"
- #include "include/core/SkFlattenable.h"
- #include "include/core/SkPoint.h"
- class SkArenaAlloc;
- class SkCanvas;
- class SkPaint;
- struct SkRect;
- class SkString;
- /** \class SkDrawLooper
- Subclasses of SkDrawLooper can be attached to a SkPaint. Where they are,
- and something is drawn to a canvas with that paint, the looper subclass will
- be called, allowing it to modify the canvas and/or paint for that draw call.
- More than that, via the next() method, the looper can modify the draw to be
- invoked multiple times (hence the name loop-er), allow it to perform effects
- like shadows or frame/fills, that require more than one pass.
- */
- class SK_API SkDrawLooper : public SkFlattenable {
- public:
- /**
- * Holds state during a draw. Users call next() until it returns false.
- *
- * Subclasses of SkDrawLooper should create a subclass of this object to
- * hold state specific to their subclass.
- */
- class SK_API Context {
- public:
- Context() {}
- virtual ~Context() {}
- /**
- * Called in a loop on objects returned by SkDrawLooper::createContext().
- * Each time true is returned, the object is drawn (possibly with a modified
- * canvas and/or paint). When false is finally returned, drawing for the object
- * stops.
- *
- * On each call, the paint will be in its original state, but the
- * canvas will be as it was following the previous call to next() or
- * createContext().
- *
- * The implementation must ensure that, when next() finally returns
- * false, the canvas has been restored to the state it was
- * initially, before createContext() was first called.
- */
- virtual bool next(SkCanvas* canvas, SkPaint* paint) = 0;
- private:
- Context(const Context&) = delete;
- Context& operator=(const Context&) = delete;
- };
- /**
- * Called right before something is being drawn. Returns a Context
- * whose next() method should be called until it returns false.
- */
- virtual Context* makeContext(SkCanvas*, SkArenaAlloc*) const = 0;
- /**
- * The fast bounds functions are used to enable the paint to be culled early
- * in the drawing pipeline. If a subclass can support this feature it must
- * return true for the canComputeFastBounds() function. If that function
- * returns false then computeFastBounds behavior is undefined otherwise it
- * is expected to have the following behavior. Given the parent paint and
- * the parent's bounding rect the subclass must fill in and return the
- * storage rect, where the storage rect is with the union of the src rect
- * and the looper's bounding rect.
- */
- bool canComputeFastBounds(const SkPaint& paint) const;
- void computeFastBounds(const SkPaint& paint, const SkRect& src, SkRect* dst) const;
- struct BlurShadowRec {
- SkScalar fSigma;
- SkVector fOffset;
- SkColor fColor;
- SkBlurStyle fStyle;
- };
- /**
- * If this looper can be interpreted as having two layers, such that
- * 1. The first layer (bottom most) just has a blur and translate
- * 2. The second layer has no modifications to either paint or canvas
- * 3. No other layers.
- * then return true, and if not null, fill out the BlurShadowRec).
- *
- * If any of the above are not met, return false and ignore the BlurShadowRec parameter.
- */
- virtual bool asABlurShadow(BlurShadowRec*) const;
- static SkFlattenable::Type GetFlattenableType() {
- return kSkDrawLooper_Type;
- }
- SkFlattenable::Type getFlattenableType() const override {
- return kSkDrawLooper_Type;
- }
- static sk_sp<SkDrawLooper> Deserialize(const void* data, size_t size,
- const SkDeserialProcs* procs = nullptr) {
- return sk_sp<SkDrawLooper>(static_cast<SkDrawLooper*>(
- SkFlattenable::Deserialize(
- kSkDrawLooper_Type, data, size, procs).release()));
- }
- void apply(SkCanvas* canvas, const SkPaint& paint,
- std::function<void(SkCanvas*, const SkPaint&)>);
- protected:
- SkDrawLooper() {}
- private:
- typedef SkFlattenable INHERITED;
- };
- #endif
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