1.1 --- /dev/null Thu Jan 01 00:00:00 1970 +0000
1.2 +++ b/gfx/skia/trunk/include/core/SkDrawLooper.h Wed Dec 31 06:09:35 2014 +0100
1.3 @@ -0,0 +1,102 @@
1.4 +
1.5 +/*
1.6 + * Copyright 2011 The Android Open Source Project
1.7 + *
1.8 + * Use of this source code is governed by a BSD-style license that can be
1.9 + * found in the LICENSE file.
1.10 + */
1.11 +
1.12 +
1.13 +#ifndef SkDrawLooper_DEFINED
1.14 +#define SkDrawLooper_DEFINED
1.15 +
1.16 +#include "SkFlattenable.h"
1.17 +
1.18 +class SkCanvas;
1.19 +class SkPaint;
1.20 +struct SkRect;
1.21 +class SkString;
1.22 +
1.23 +/** \class SkDrawLooper
1.24 + Subclasses of SkDrawLooper can be attached to a SkPaint. Where they are,
1.25 + and something is drawn to a canvas with that paint, the looper subclass will
1.26 + be called, allowing it to modify the canvas and/or paint for that draw call.
1.27 + More than that, via the next() method, the looper can modify the draw to be
1.28 + invoked multiple times (hence the name loop-er), allow it to perform effects
1.29 + like shadows or frame/fills, that require more than one pass.
1.30 +*/
1.31 +class SK_API SkDrawLooper : public SkFlattenable {
1.32 +public:
1.33 + SK_DECLARE_INST_COUNT(SkDrawLooper)
1.34 +
1.35 + /**
1.36 + * Holds state during a draw. Users call next() until it returns false.
1.37 + *
1.38 + * Subclasses of SkDrawLooper should create a subclass of this object to
1.39 + * hold state specific to their subclass.
1.40 + */
1.41 + class SK_API Context : public SkNoncopyable {
1.42 + public:
1.43 + Context() {}
1.44 + virtual ~Context() {}
1.45 +
1.46 + /**
1.47 + * Called in a loop on objects returned by SkDrawLooper::createContext().
1.48 + * Each time true is returned, the object is drawn (possibly with a modified
1.49 + * canvas and/or paint). When false is finally returned, drawing for the object
1.50 + * stops.
1.51 + *
1.52 + * On each call, the paint will be in its original state, but the
1.53 + * canvas will be as it was following the previous call to next() or
1.54 + * createContext().
1.55 + *
1.56 + * The implementation must ensure that, when next() finally returns
1.57 + * false, the canvas has been restored to the state it was
1.58 + * initially, before createContext() was first called.
1.59 + */
1.60 + virtual bool next(SkCanvas* canvas, SkPaint* paint) = 0;
1.61 + };
1.62 +
1.63 + /**
1.64 + * Called right before something is being drawn. Returns a Context
1.65 + * whose next() method should be called until it returns false.
1.66 + * The caller has to ensure that the storage pointer provides enough
1.67 + * memory for the Context. The required size can be queried by calling
1.68 + * contextSize(). It is also the caller's responsibility to destroy the
1.69 + * object after use.
1.70 + */
1.71 + virtual Context* createContext(SkCanvas*, void* storage) const = 0;
1.72 +
1.73 + /**
1.74 + * Returns the number of bytes needed to store subclasses of Context (belonging to the
1.75 + * corresponding SkDrawLooper subclass).
1.76 + */
1.77 + virtual size_t contextSize() const = 0;
1.78 +
1.79 +
1.80 + /**
1.81 + * The fast bounds functions are used to enable the paint to be culled early
1.82 + * in the drawing pipeline. If a subclass can support this feature it must
1.83 + * return true for the canComputeFastBounds() function. If that function
1.84 + * returns false then computeFastBounds behavior is undefined otherwise it
1.85 + * is expected to have the following behavior. Given the parent paint and
1.86 + * the parent's bounding rect the subclass must fill in and return the
1.87 + * storage rect, where the storage rect is with the union of the src rect
1.88 + * and the looper's bounding rect.
1.89 + */
1.90 + virtual bool canComputeFastBounds(const SkPaint& paint) const;
1.91 + virtual void computeFastBounds(const SkPaint& paint,
1.92 + const SkRect& src, SkRect* dst) const;
1.93 +
1.94 + SK_TO_STRING_PUREVIRT()
1.95 + SK_DEFINE_FLATTENABLE_TYPE(SkDrawLooper)
1.96 +
1.97 +protected:
1.98 + SkDrawLooper() {}
1.99 + SkDrawLooper(SkReadBuffer& buffer) : INHERITED(buffer) {}
1.100 +
1.101 +private:
1.102 + typedef SkFlattenable INHERITED;
1.103 +};
1.104 +
1.105 +#endif
