SkPathEffect.h revision ec3ed6a5ebf6f2c406d7bcf94b6bc34fcaeb976e 
1
2/*
3 * Copyright 2006 The Android Open Source Project
4 *
5 * Use of this source code is governed by a BSD-style license that can be
6 * found in the LICENSE file.
7 */
8
9
10#ifndef SkPathEffect_DEFINED
11#define SkPathEffect_DEFINED
12
13#include "SkFlattenable.h"
14
15class SkPath;
16
17/** \class SkPathEffect
18
19    SkPathEffect is the base class for objects in the SkPaint that affect
20    the geometry of a drawing primitive before it is transformed by the
21    canvas' matrix and drawn.
22
23    Dashing is implemented as a subclass of SkPathEffect.
24*/
25class SK_API SkPathEffect : public SkFlattenable {
26public:
27    SkPathEffect() {}
28
29    /** Given a src path and a width value, return true if the patheffect
30        has produced a new path (dst) and a new width value. If false is returned,
31        ignore dst and width.
32        On input, width >= 0 means the src should be stroked
33        On output, width >= 0 means the dst should be stroked
34    */
35    virtual bool filterPath(SkPath* dst, const SkPath& src, SkScalar* width) = 0;
36
37private:
38    // illegal
39    SkPathEffect(const SkPathEffect&);
40    SkPathEffect& operator=(const SkPathEffect&);
41};
42
43/** \class SkPairPathEffect
44
45    Common baseclass for Compose and Sum. This subclass manages two pathEffects,
46    including flattening them. It does nothing in filterPath, and is only useful
47    for managing the lifetimes of its two arguments.
48*/
49class SkPairPathEffect : public SkPathEffect {
50public:
51    SkPairPathEffect(SkPathEffect* pe0, SkPathEffect* pe1);
52    virtual ~SkPairPathEffect();
53
54protected:
55    SkPairPathEffect(SkFlattenableReadBuffer&);
56    virtual void flatten(SkFlattenableWriteBuffer&);
57    // these are visible to our subclasses
58    SkPathEffect* fPE0, *fPE1;
59
60private:
61    typedef SkPathEffect INHERITED;
62};
63
64/** \class SkComposePathEffect
65
66    This subclass of SkPathEffect composes its two arguments, to create
67    a compound pathEffect.
68*/
69class SkComposePathEffect : public SkPairPathEffect {
70public:
71    /** Construct a pathEffect whose effect is to apply first the inner pathEffect
72        and the the outer pathEffect (e.g. outer(inner(path)))
73        The reference counts for outer and inner are both incremented in the constructor,
74        and decremented in the destructor.
75    */
76    SkComposePathEffect(SkPathEffect* outer, SkPathEffect* inner)
77        : INHERITED(outer, inner) {}
78
79    // overrides
80
81    virtual bool filterPath(SkPath* dst, const SkPath& src, SkScalar* width);
82
83    static SkFlattenable* CreateProc(SkFlattenableReadBuffer& buffer) {
84        return SkNEW_ARGS(SkComposePathEffect, (buffer));
85    }
86
87protected:
88    virtual Factory getFactory() { return CreateProc; }
89
90private:
91    SkComposePathEffect(SkFlattenableReadBuffer& buffer) : INHERITED(buffer) {}
92
93    // illegal
94    SkComposePathEffect(const SkComposePathEffect&);
95    SkComposePathEffect& operator=(const SkComposePathEffect&);
96
97    typedef SkPairPathEffect INHERITED;
98};
99
100/** \class SkSumPathEffect
101
102    This subclass of SkPathEffect applies two pathEffects, one after the other.
103    Its filterPath() returns true if either of the effects succeeded.
104*/
105class SkSumPathEffect : public SkPairPathEffect {
106public:
107    /** Construct a pathEffect whose effect is to apply two effects, in sequence.
108        (e.g. first(path) + second(path))
109        The reference counts for first and second are both incremented in the constructor,
110        and decremented in the destructor.
111    */
112    SkSumPathEffect(SkPathEffect* first, SkPathEffect* second)
113        : INHERITED(first, second) {}
114
115    // overrides
116    virtual bool filterPath(SkPath* dst, const SkPath& src, SkScalar* width);
117
118    static SkFlattenable* CreateProc(SkFlattenableReadBuffer& buffer)  {
119        return SkNEW_ARGS(SkSumPathEffect, (buffer));
120    }
121
122protected:
123    virtual Factory getFactory() { return CreateProc; }
124
125private:
126    SkSumPathEffect(SkFlattenableReadBuffer& buffer) : INHERITED(buffer) {}
127
128    // illegal
129    SkSumPathEffect(const SkSumPathEffect&);
130    SkSumPathEffect& operator=(const SkSumPathEffect&);
131
132    typedef SkPairPathEffect INHERITED;
133};
134
135#endif
136
137