SkPathEffect.h revision 4bbdeac58cc928dc66296bde3bd06e78070d96b7 
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#include "SkPath.h"
15#include "SkPoint.h"
16#include "SkRect.h"
17#include "SkStrokeRec.h"
18#include "SkTDArray.h"
19
20class SkPath;
21
22/** \class SkPathEffect
23
24    SkPathEffect is the base class for objects in the SkPaint that affect
25    the geometry of a drawing primitive before it is transformed by the
26    canvas' matrix and drawn.
27
28    Dashing is implemented as a subclass of SkPathEffect.
29*/
30class SK_API SkPathEffect : public SkFlattenable {
31public:
32    SK_DECLARE_INST_COUNT(SkPathEffect)
33
34    SkPathEffect() {}
35
36    /**
37     *  Given a src path (input) and a stroke-rec (input and output), apply
38     *  this effect to the src path, returning the new path in dst, and return
39     *  true. If this effect cannot be applied, return false and ignore dst
40     *  and stroke-rec.
41     *
42     *  The stroke-rec specifies the initial request for stroking (if any).
43     *  The effect can treat this as input only, or it can choose to change
44     *  the rec as well. For example, the effect can decide to change the
45     *  stroke's width or join, or the effect can change the rec from stroke
46     *  to fill (or fill to stroke) in addition to returning a new (dst) path.
47     *
48     *  If this method returns true, the caller will apply (as needed) the
49     *  resulting stroke-rec to dst and then draw.
50     */
51    virtual bool filterPath(SkPath* dst, const SkPath& src,
52                            SkStrokeRec*, const SkRect* cullR) const = 0;
53
54    /**
55     *  Compute a conservative bounds for its effect, given the src bounds.
56     *  The baseline implementation just assigns src to dst.
57     */
58    virtual void computeFastBounds(SkRect* dst, const SkRect& src) const;
59
60    /** \class PointData
61
62        PointData aggregates all the information needed to draw the point
63        primitives returned by an 'asPoints' call.
64    */
65    class PointData {
66    public:
67        PointData()
68            : fFlags(0)
69            , fPoints(NULL)
70            , fNumPoints(0) {
71            fSize.set(SK_Scalar1, SK_Scalar1);
72            // 'asPoints' needs to initialize/fill-in 'fClipRect' if it sets
73            // the kUseClip flag
74        };
75        ~PointData() {
76            delete [] fPoints;
77        }
78
79        // TODO: consider using passed-in flags to limit the work asPoints does.
80        // For example, a kNoPath flag could indicate don't bother generating
81        // stamped solutions.
82
83        // Currently none of these flags are supported.
84        enum PointFlags {
85            kCircles_PointFlag            = 0x01,   // draw points as circles (instead of rects)
86            kUsePath_PointFlag            = 0x02,   // draw points as stamps of the returned path
87            kUseClip_PointFlag            = 0x04,   // apply 'fClipRect' before drawing the points
88        };
89
90        uint32_t           fFlags;      // flags that impact the drawing of the points
91        SkPoint*           fPoints;     // the center point of each generated point
92        int                fNumPoints;  // number of points in fPoints
93        SkVector           fSize;       // the size to draw the points
94        SkRect             fClipRect;   // clip required to draw the points (if kUseClip is set)
95        SkPath             fPath;       // 'stamp' to be used at each point (if kUsePath is set)
96
97        SkPath             fFirst;      // If not empty, contains geometry for first point
98        SkPath             fLast;       // If not empty, contains geometry for last point
99    };
100
101    /**
102     *  Does applying this path effect to 'src' yield a set of points? If so,
103     *  optionally return the points in 'results'.
104     */
105    virtual bool asPoints(PointData* results, const SkPath& src,
106                          const SkStrokeRec&, const SkMatrix&,
107                          const SkRect* cullR) const;
108
109protected:
110    SkPathEffect(SkFlattenableReadBuffer& buffer) : INHERITED(buffer) {}
111
112private:
113    // illegal
114    SkPathEffect(const SkPathEffect&);
115    SkPathEffect& operator=(const SkPathEffect&);
116
117    typedef SkFlattenable INHERITED;
118};
119
120/** \class SkPairPathEffect
121
122    Common baseclass for Compose and Sum. This subclass manages two pathEffects,
123    including flattening them. It does nothing in filterPath, and is only useful
124    for managing the lifetimes of its two arguments.
125*/
126class SkPairPathEffect : public SkPathEffect {
127public:
128    SkPairPathEffect(SkPathEffect* pe0, SkPathEffect* pe1);
129    virtual ~SkPairPathEffect();
130
131protected:
132    SkPairPathEffect(SkFlattenableReadBuffer&);
133    virtual void flatten(SkFlattenableWriteBuffer&) const SK_OVERRIDE;
134
135    // these are visible to our subclasses
136    SkPathEffect* fPE0, *fPE1;
137
138private:
139    typedef SkPathEffect INHERITED;
140};
141
142/** \class SkComposePathEffect
143
144    This subclass of SkPathEffect composes its two arguments, to create
145    a compound pathEffect.
146*/
147class SkComposePathEffect : public SkPairPathEffect {
148public:
149    /** Construct a pathEffect whose effect is to apply first the inner pathEffect
150        and the the outer pathEffect (e.g. outer(inner(path)))
151        The reference counts for outer and inner are both incremented in the constructor,
152        and decremented in the destructor.
153    */
154    SkComposePathEffect(SkPathEffect* outer, SkPathEffect* inner)
155        : INHERITED(outer, inner) {}
156
157    virtual bool filterPath(SkPath* dst, const SkPath& src,
158                            SkStrokeRec*, const SkRect*) const SK_OVERRIDE;
159
160    SK_DECLARE_PUBLIC_FLATTENABLE_DESERIALIZATION_PROCS(SkComposePathEffect)
161
162protected:
163    SkComposePathEffect(SkFlattenableReadBuffer& buffer) : INHERITED(buffer) {}
164
165private:
166    // illegal
167    SkComposePathEffect(const SkComposePathEffect&);
168    SkComposePathEffect& operator=(const SkComposePathEffect&);
169
170    typedef SkPairPathEffect INHERITED;
171};
172
173/** \class SkSumPathEffect
174
175    This subclass of SkPathEffect applies two pathEffects, one after the other.
176    Its filterPath() returns true if either of the effects succeeded.
177*/
178class SkSumPathEffect : public SkPairPathEffect {
179public:
180    /** Construct a pathEffect whose effect is to apply two effects, in sequence.
181        (e.g. first(path) + second(path))
182        The reference counts for first and second are both incremented in the constructor,
183        and decremented in the destructor.
184    */
185    SkSumPathEffect(SkPathEffect* first, SkPathEffect* second)
186        : INHERITED(first, second) {}
187
188    virtual bool filterPath(SkPath* dst, const SkPath& src,
189                            SkStrokeRec*, const SkRect*) const SK_OVERRIDE;
190
191    SK_DECLARE_PUBLIC_FLATTENABLE_DESERIALIZATION_PROCS(SkSumPathEffect)
192
193protected:
194    SkSumPathEffect(SkFlattenableReadBuffer& buffer) : INHERITED(buffer) {}
195
196private:
197    // illegal
198    SkSumPathEffect(const SkSumPathEffect&);
199    SkSumPathEffect& operator=(const SkSumPathEffect&);
200
201    typedef SkPairPathEffect INHERITED;
202};
203
204#endif
205
206