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1 
2 /*
3  * Copyright 2012 Google Inc.
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 #ifndef SkPathRef_DEFINED
10 #define SkPathRef_DEFINED
11 
12 #include "SkMatrix.h"
13 #include "SkPoint.h"
14 #include "SkRect.h"
15 #include "SkRefCnt.h"
16 #include "SkTDArray.h"
17 #include <stddef.h> // ptrdiff_t
18 
19 class SkRBuffer;
20 class SkWBuffer;
21 
22 /**
23  * Holds the path verbs and points. It is versioned by a generation ID. None of its public methods
24  * modify the contents. To modify or append to the verbs/points wrap the SkPathRef in an
25  * SkPathRef::Editor object. Installing the editor resets the generation ID. It also performs
26  * copy-on-write if the SkPathRef is shared by multiple SkPaths. The caller passes the Editor's
27  * constructor a SkAutoTUnref, which may be updated to point to a new SkPathRef after the editor's
28  * constructor returns.
29  *
30  * The points and verbs are stored in a single allocation. The points are at the begining of the
31  * allocation while the verbs are stored at end of the allocation, in reverse order. Thus the points
32  * and verbs both grow into the middle of the allocation until the meet. To access verb i in the
33  * verb array use ref.verbs()[~i] (because verbs() returns a pointer just beyond the first
34  * logical verb or the last verb in memory).
35  */
36 
37 class SK_API SkPathRef : public ::SkRefCnt {
38 public:
39     SK_DECLARE_INST_COUNT(SkPathRef);
40 
41     class Editor {
42     public:
43         Editor(SkAutoTUnref<SkPathRef>* pathRef,
44                int incReserveVerbs = 0,
45                int incReservePoints = 0);
46 
~Editor()47         ~Editor() { SkDEBUGCODE(sk_atomic_dec(&fPathRef->fEditorsAttached);) }
48 
49         /**
50          * Returns the array of points.
51          */
points()52         SkPoint* points() { return fPathRef->getPoints(); }
points()53         const SkPoint* points() const { return fPathRef->points(); }
54 
55         /**
56          * Gets the ith point. Shortcut for this->points() + i
57          */
atPoint(int i)58         SkPoint* atPoint(int i) {
59             SkASSERT((unsigned) i < (unsigned) fPathRef->fPointCnt);
60             return this->points() + i;
61         };
atPoint(int i)62         const SkPoint* atPoint(int i) const {
63             SkASSERT((unsigned) i < (unsigned) fPathRef->fPointCnt);
64             return this->points() + i;
65         };
66 
67         /**
68          * Adds the verb and allocates space for the number of points indicated by the verb. The
69          * return value is a pointer to where the points for the verb should be written.
70          * 'weight' is only used if 'verb' is kConic_Verb
71          */
72         SkPoint* growForVerb(int /*SkPath::Verb*/ verb, SkScalar weight = 0) {
73             SkDEBUGCODE(fPathRef->validate();)
74             return fPathRef->growForVerb(verb, weight);
75         }
76 
77         /**
78          * Allocates space for multiple instances of a particular verb and the
79          * requisite points & weights.
80          * The return pointer points at the first new point (indexed normally [<i>]).
81          * If 'verb' is kConic_Verb, 'weights' will return a pointer to the
82          * space for the conic weights (indexed normally).
83          */
84         SkPoint* growForRepeatedVerb(int /*SkPath::Verb*/ verb,
85                                      int numVbs,
86                                      SkScalar** weights = NULL) {
87             return fPathRef->growForRepeatedVerb(verb, numVbs, weights);
88         }
89 
90         /**
91          * Resets the path ref to a new verb and point count. The new verbs and points are
92          * uninitialized.
93          */
resetToSize(int newVerbCnt,int newPointCnt,int newConicCount)94         void resetToSize(int newVerbCnt, int newPointCnt, int newConicCount) {
95             fPathRef->resetToSize(newVerbCnt, newPointCnt, newConicCount);
96         }
97 
98         /**
99          * Gets the path ref that is wrapped in the Editor.
100          */
pathRef()101         SkPathRef* pathRef() { return fPathRef; }
102 
setIsOval(bool isOval)103         void setIsOval(bool isOval) { fPathRef->setIsOval(isOval); }
104 
setBounds(const SkRect & rect)105         void setBounds(const SkRect& rect) { fPathRef->setBounds(rect); }
106 
107     private:
108         SkPathRef* fPathRef;
109     };
110 
111 public:
112     /**
113      * Gets a path ref with no verbs or points.
114      */
115     static SkPathRef* CreateEmpty();
116 
117     /**
118      *  Returns true if all of the points in this path are finite, meaning there
119      *  are no infinities and no NaNs.
120      */
isFinite()121     bool isFinite() const {
122         if (fBoundsIsDirty) {
123             this->computeBounds();
124         }
125         return SkToBool(fIsFinite);
126     }
127 
128     /**
129      *  Returns a mask, where each bit corresponding to a SegmentMask is
130      *  set if the path contains 1 or more segments of that type.
131      *  Returns 0 for an empty path (no segments).
132      */
getSegmentMasks()133     uint32_t getSegmentMasks() const { return fSegmentMask; }
134 
135     /** Returns true if the path is an oval.
136      *
137      * @param rect      returns the bounding rect of this oval. It's a circle
138      *                  if the height and width are the same.
139      *
140      * @return true if this path is an oval.
141      *              Tracking whether a path is an oval is considered an
142      *              optimization for performance and so some paths that are in
143      *              fact ovals can report false.
144      */
isOval(SkRect * rect)145     bool isOval(SkRect* rect) const {
146         if (fIsOval && NULL != rect) {
147             *rect = getBounds();
148         }
149 
150         return SkToBool(fIsOval);
151     }
152 
hasComputedBounds()153     bool hasComputedBounds() const {
154         return !fBoundsIsDirty;
155     }
156 
157     /** Returns the bounds of the path's points. If the path contains 0 or 1
158         points, the bounds is set to (0,0,0,0), and isEmpty() will return true.
159         Note: this bounds may be larger than the actual shape, since curves
160         do not extend as far as their control points.
161     */
getBounds()162     const SkRect& getBounds() const {
163         if (fBoundsIsDirty) {
164             this->computeBounds();
165         }
166         return fBounds;
167     }
168 
169     /**
170      * Transforms a path ref by a matrix, allocating a new one only if necessary.
171      */
172     static void CreateTransformedCopy(SkAutoTUnref<SkPathRef>* dst,
173                                       const SkPathRef& src,
174                                       const SkMatrix& matrix);
175 
176     static SkPathRef* CreateFromBuffer(SkRBuffer* buffer);
177 
178     /**
179      * Rollsback a path ref to zero verbs and points with the assumption that the path ref will be
180      * repopulated with approximately the same number of verbs and points. A new path ref is created
181      * only if necessary.
182      */
183     static void Rewind(SkAutoTUnref<SkPathRef>* pathRef);
184 
~SkPathRef()185     virtual ~SkPathRef() {
186         SkDEBUGCODE(this->validate();)
187         sk_free(fPoints);
188 
189         SkDEBUGCODE(fPoints = NULL;)
190         SkDEBUGCODE(fVerbs = NULL;)
191         SkDEBUGCODE(fVerbCnt = 0x9999999;)
192         SkDEBUGCODE(fPointCnt = 0xAAAAAAA;)
193         SkDEBUGCODE(fPointCnt = 0xBBBBBBB;)
194         SkDEBUGCODE(fGenerationID = 0xEEEEEEEE;)
195         SkDEBUGCODE(fEditorsAttached = 0x7777777;)
196     }
197 
countPoints()198     int countPoints() const { SkDEBUGCODE(this->validate();) return fPointCnt; }
countVerbs()199     int countVerbs() const { SkDEBUGCODE(this->validate();) return fVerbCnt; }
countWeights()200     int countWeights() const { SkDEBUGCODE(this->validate();) return fConicWeights.count(); }
201 
202     /**
203      * Returns a pointer one beyond the first logical verb (last verb in memory order).
204      */
verbs()205     const uint8_t* verbs() const { SkDEBUGCODE(this->validate();) return fVerbs; }
206 
207     /**
208      * Returns a const pointer to the first verb in memory (which is the last logical verb).
209      */
verbsMemBegin()210     const uint8_t* verbsMemBegin() const { return this->verbs() - fVerbCnt; }
211 
212     /**
213      * Returns a const pointer to the first point.
214      */
points()215     const SkPoint* points() const { SkDEBUGCODE(this->validate();) return fPoints; }
216 
217     /**
218      * Shortcut for this->points() + this->countPoints()
219      */
pointsEnd()220     const SkPoint* pointsEnd() const { return this->points() + this->countPoints(); }
221 
conicWeights()222     const SkScalar* conicWeights() const { SkDEBUGCODE(this->validate();) return fConicWeights.begin(); }
conicWeightsEnd()223     const SkScalar* conicWeightsEnd() const { SkDEBUGCODE(this->validate();) return fConicWeights.end(); }
224 
225     /**
226      * Convenience methods for getting to a verb or point by index.
227      */
atVerb(int index)228     uint8_t atVerb(int index) const {
229         SkASSERT((unsigned) index < (unsigned) fVerbCnt);
230         return this->verbs()[~index];
231     }
atPoint(int index)232     const SkPoint& atPoint(int index) const {
233         SkASSERT((unsigned) index < (unsigned) fPointCnt);
234         return this->points()[index];
235     }
236 
237     bool operator== (const SkPathRef& ref) const;
238 
239     /**
240      * Writes the path points and verbs to a buffer.
241      */
242     void writeToBuffer(SkWBuffer* buffer) const;
243 
244     /**
245      * Gets the number of bytes that would be written in writeBuffer()
246      */
247     uint32_t writeSize() const;
248 
249     /**
250      * Gets an ID that uniquely identifies the contents of the path ref. If two path refs have the
251      * same ID then they have the same verbs and points. However, two path refs may have the same
252      * contents but different genIDs.
253      */
254     uint32_t genID() const;
255 
256 private:
257     enum SerializationOffsets {
258         kIsFinite_SerializationShift = 25,  // requires 1 bit
259         kIsOval_SerializationShift = 24,    // requires 1 bit
260         kSegmentMask_SerializationShift = 0 // requires 4 bits
261     };
262 
SkPathRef()263     SkPathRef() {
264         fBoundsIsDirty = true;    // this also invalidates fIsFinite
265         fPointCnt = 0;
266         fVerbCnt = 0;
267         fVerbs = NULL;
268         fPoints = NULL;
269         fFreeSpace = 0;
270         fGenerationID = kEmptyGenID;
271         fSegmentMask = 0;
272         fIsOval = false;
273         SkDEBUGCODE(fEditorsAttached = 0;)
274         SkDEBUGCODE(this->validate();)
275     }
276 
277     void copy(const SkPathRef& ref, int additionalReserveVerbs, int additionalReservePoints);
278 
279     // Return true if the computed bounds are finite.
ComputePtBounds(SkRect * bounds,const SkPathRef & ref)280     static bool ComputePtBounds(SkRect* bounds, const SkPathRef& ref) {
281         int count = ref.countPoints();
282         if (count <= 1) {  // we ignore just 1 point (moveto)
283             bounds->setEmpty();
284             return count ? ref.points()->isFinite() : true;
285         } else {
286             return bounds->setBoundsCheck(ref.points(), count);
287         }
288     }
289 
290     // called, if dirty, by getBounds()
computeBounds()291     void computeBounds() const {
292         SkDEBUGCODE(this->validate();)
293         SkASSERT(fBoundsIsDirty);
294 
295         fIsFinite = ComputePtBounds(&fBounds, *this);
296         fBoundsIsDirty = false;
297     }
298 
setBounds(const SkRect & rect)299     void setBounds(const SkRect& rect) {
300         SkASSERT(rect.fLeft <= rect.fRight && rect.fTop <= rect.fBottom);
301         fBounds = rect;
302         fBoundsIsDirty = false;
303         fIsFinite = fBounds.isFinite();
304     }
305 
306     /** Makes additional room but does not change the counts or change the genID */
incReserve(int additionalVerbs,int additionalPoints)307     void incReserve(int additionalVerbs, int additionalPoints) {
308         SkDEBUGCODE(this->validate();)
309         size_t space = additionalVerbs * sizeof(uint8_t) + additionalPoints * sizeof (SkPoint);
310         this->makeSpace(space);
311         SkDEBUGCODE(this->validate();)
312     }
313 
314     /** Resets the path ref with verbCount verbs and pointCount points, all uninitialized. Also
315      *  allocates space for reserveVerb additional verbs and reservePoints additional points.*/
316     void resetToSize(int verbCount, int pointCount, int conicCount,
317                      int reserveVerbs = 0, int reservePoints = 0) {
318         SkDEBUGCODE(this->validate();)
319         fBoundsIsDirty = true;      // this also invalidates fIsFinite
320         fGenerationID = 0;
321 
322         fSegmentMask = 0;
323         fIsOval = false;
324 
325         size_t newSize = sizeof(uint8_t) * verbCount + sizeof(SkPoint) * pointCount;
326         size_t newReserve = sizeof(uint8_t) * reserveVerbs + sizeof(SkPoint) * reservePoints;
327         size_t minSize = newSize + newReserve;
328 
329         ptrdiff_t sizeDelta = this->currSize() - minSize;
330 
331         if (sizeDelta < 0 || static_cast<size_t>(sizeDelta) >= 3 * minSize) {
332             sk_free(fPoints);
333             fPoints = NULL;
334             fVerbs = NULL;
335             fFreeSpace = 0;
336             fVerbCnt = 0;
337             fPointCnt = 0;
338             this->makeSpace(minSize);
339             fVerbCnt = verbCount;
340             fPointCnt = pointCount;
341             fFreeSpace -= newSize;
342         } else {
343             fPointCnt = pointCount;
344             fVerbCnt = verbCount;
345             fFreeSpace = this->currSize() - minSize;
346         }
347         fConicWeights.setCount(conicCount);
348         SkDEBUGCODE(this->validate();)
349     }
350 
351     /**
352      * Increases the verb count by numVbs and point count by the required amount.
353      * The new points are uninitialized. All the new verbs are set to the specified
354      * verb. If 'verb' is kConic_Verb, 'weights' will return a pointer to the
355      * uninitialized conic weights.
356      */
357     SkPoint* growForRepeatedVerb(int /*SkPath::Verb*/ verb, int numVbs, SkScalar** weights);
358 
359     /**
360      * Increases the verb count 1, records the new verb, and creates room for the requisite number
361      * of additional points. A pointer to the first point is returned. Any new points are
362      * uninitialized.
363      */
364     SkPoint* growForVerb(int /*SkPath::Verb*/ verb, SkScalar weight);
365 
366     /**
367      * Ensures that the free space available in the path ref is >= size. The verb and point counts
368      * are not changed.
369      */
makeSpace(size_t size)370     void makeSpace(size_t size) {
371         SkDEBUGCODE(this->validate();)
372         ptrdiff_t growSize = size - fFreeSpace;
373         if (growSize <= 0) {
374             return;
375         }
376         size_t oldSize = this->currSize();
377         // round to next multiple of 8 bytes
378         growSize = (growSize + 7) & ~static_cast<size_t>(7);
379         // we always at least double the allocation
380         if (static_cast<size_t>(growSize) < oldSize) {
381             growSize = oldSize;
382         }
383         if (growSize < kMinSize) {
384             growSize = kMinSize;
385         }
386         size_t newSize = oldSize + growSize;
387         // Note that realloc could memcpy more than we need. It seems to be a win anyway. TODO:
388         // encapsulate this.
389         fPoints = reinterpret_cast<SkPoint*>(sk_realloc_throw(fPoints, newSize));
390         size_t oldVerbSize = fVerbCnt * sizeof(uint8_t);
391         void* newVerbsDst = reinterpret_cast<void*>(
392                                 reinterpret_cast<intptr_t>(fPoints) + newSize - oldVerbSize);
393         void* oldVerbsSrc = reinterpret_cast<void*>(
394                                 reinterpret_cast<intptr_t>(fPoints) + oldSize - oldVerbSize);
395         memmove(newVerbsDst, oldVerbsSrc, oldVerbSize);
396         fVerbs = reinterpret_cast<uint8_t*>(reinterpret_cast<intptr_t>(fPoints) + newSize);
397         fFreeSpace += growSize;
398         SkDEBUGCODE(this->validate();)
399     }
400 
401     /**
402      * Private, non-const-ptr version of the public function verbsMemBegin().
403      */
verbsMemWritable()404     uint8_t* verbsMemWritable() {
405         SkDEBUGCODE(this->validate();)
406         return fVerbs - fVerbCnt;
407     }
408 
409     /**
410      * Gets the total amount of space allocated for verbs, points, and reserve.
411      */
currSize()412     size_t currSize() const {
413         return reinterpret_cast<intptr_t>(fVerbs) - reinterpret_cast<intptr_t>(fPoints);
414     }
415 
416     SkDEBUGCODE(void validate() const;)
417 
418     /**
419      * Called the first time someone calls CreateEmpty to actually create the singleton.
420      */
421     static SkPathRef* CreateEmptyImpl();
422 
setIsOval(bool isOval)423     void setIsOval(bool isOval) { fIsOval = isOval; }
424 
getPoints()425     SkPoint* getPoints() {
426         SkDEBUGCODE(this->validate();)
427         fIsOval = false;
428         return fPoints;
429     }
430 
431     enum {
432         kMinSize = 256,
433     };
434 
435     mutable SkRect      fBounds;
436     uint8_t             fSegmentMask;
437     mutable uint8_t     fBoundsIsDirty;
438     mutable SkBool8     fIsFinite;    // only meaningful if bounds are valid
439     mutable SkBool8     fIsOval;
440 
441     SkPoint*            fPoints; // points to begining of the allocation
442     uint8_t*            fVerbs; // points just past the end of the allocation (verbs grow backwards)
443     int                 fVerbCnt;
444     int                 fPointCnt;
445     size_t              fFreeSpace; // redundant but saves computation
446     SkTDArray<SkScalar> fConicWeights;
447 
448     enum {
449         kEmptyGenID = 1, // GenID reserved for path ref with zero points and zero verbs.
450     };
451     mutable uint32_t    fGenerationID;
452     SkDEBUGCODE(int32_t fEditorsAttached;) // assert that only one editor in use at any time.
453 
454     friend class PathRefTest_Private;
455     typedef SkRefCnt INHERITED;
456 };
457 
458 #endif
459