3 * Copyright 2011 The Android Open Source Project
5 * Use of this source code is governed by a BSD-style license that can be
6 * found in the LICENSE file.
10 #ifndef SkDrawLooper_DEFINED
11 #define SkDrawLooper_DEFINED
13 #include "SkBlurTypes.h"
14 #include "SkFlattenable.h"
23 /** \class SkDrawLooper
24 Subclasses of SkDrawLooper can be attached to a SkPaint. Where they are,
25 and something is drawn to a canvas with that paint, the looper subclass will
26 be called, allowing it to modify the canvas and/or paint for that draw call.
27 More than that, via the next() method, the looper can modify the draw to be
28 invoked multiple times (hence the name loop-er), allow it to perform effects
29 like shadows or frame/fills, that require more than one pass.
31 class SK_API SkDrawLooper : public SkFlattenable {
33 SK_DECLARE_INST_COUNT(SkDrawLooper)
36 * Holds state during a draw. Users call next() until it returns false.
38 * Subclasses of SkDrawLooper should create a subclass of this object to
39 * hold state specific to their subclass.
41 class SK_API Context : ::SkNoncopyable {
47 * Called in a loop on objects returned by SkDrawLooper::createContext().
48 * Each time true is returned, the object is drawn (possibly with a modified
49 * canvas and/or paint). When false is finally returned, drawing for the object
52 * On each call, the paint will be in its original state, but the
53 * canvas will be as it was following the previous call to next() or
56 * The implementation must ensure that, when next() finally returns
57 * false, the canvas has been restored to the state it was
58 * initially, before createContext() was first called.
60 virtual bool next(SkCanvas* canvas, SkPaint* paint) = 0;
64 * Called right before something is being drawn. Returns a Context
65 * whose next() method should be called until it returns false.
66 * The caller has to ensure that the storage pointer provides enough
67 * memory for the Context. The required size can be queried by calling
68 * contextSize(). It is also the caller's responsibility to destroy the
71 virtual Context* createContext(SkCanvas*, void* storage) const = 0;
74 * Returns the number of bytes needed to store subclasses of Context (belonging to the
75 * corresponding SkDrawLooper subclass).
77 virtual size_t contextSize() const = 0;
81 * The fast bounds functions are used to enable the paint to be culled early
82 * in the drawing pipeline. If a subclass can support this feature it must
83 * return true for the canComputeFastBounds() function. If that function
84 * returns false then computeFastBounds behavior is undefined otherwise it
85 * is expected to have the following behavior. Given the parent paint and
86 * the parent's bounding rect the subclass must fill in and return the
87 * storage rect, where the storage rect is with the union of the src rect
88 * and the looper's bounding rect.
90 virtual bool canComputeFastBounds(const SkPaint& paint) const;
91 virtual void computeFastBounds(const SkPaint& paint,
92 const SkRect& src, SkRect* dst) const;
94 struct BlurShadowRec {
99 SkBlurQuality fQuality;
102 * If this looper can be interpreted as having two layers, such that
103 * 1. The first layer (bottom most) just has a blur and translate
104 * 2. The second layer has no modifications to either paint or canvas
105 * 3. No other layers.
106 * then return true, and if not null, fill out the BlurShadowRec).
108 * If any of the above are not met, return false and ignore the BlurShadowRec parameter.
110 virtual bool asABlurShadow(BlurShadowRec*) const;
112 SK_TO_STRING_PUREVIRT()
113 SK_DEFINE_FLATTENABLE_TYPE(SkDrawLooper)
117 #ifdef SK_SUPPORT_LEGACY_DEEPFLATTENING
118 SkDrawLooper(SkReadBuffer& buffer) : INHERITED(buffer) {}
122 typedef SkFlattenable INHERITED;