GrClipMaskManager.h revision 427cf28861867c0ea9aafca3a23878ec4068ad99 
1/*
2 * Copyright 2012 Google Inc.
3 *
4 * Use of this source code is governed by a BSD-style license that can be
5 * found in the LICENSE file.
6 */
7
8#ifndef GrClipMaskManager_DEFINED
9#define GrClipMaskManager_DEFINED
10
11#include "GrClipMaskCache.h"
12#include "GrContext.h"
13#include "GrDrawState.h"
14#include "GrReducedClip.h"
15#include "GrStencil.h"
16#include "GrTexture.h"
17
18#include "SkClipStack.h"
19#include "SkDeque.h"
20#include "SkPath.h"
21#include "SkRefCnt.h"
22#include "SkTLList.h"
23#include "SkTypes.h"
24
25class GrGpu;
26class GrPathRenderer;
27class GrPathRendererChain;
28class GrTexture;
29class SkPath;
30
31/**
32 * The clip mask creator handles the generation of the clip mask. If anti
33 * aliasing is requested it will (in the future) generate a single channel
34 * (8bit) mask. If no anti aliasing is requested it will generate a 1-bit
35 * mask in the stencil buffer. In the non anti-aliasing case, if the clip
36 * mask can be represented as a rectangle then scissoring is used. In all
37 * cases scissoring is used to bound the range of the clip mask.
38 */
39class GrClipMaskManager : SkNoncopyable {
40public:
41    GrClipMaskManager()
42        : fGpu(NULL)
43        , fCurrClipMaskType(kNone_ClipMaskType) {
44    }
45
46    /**
47     * Creates a clip mask if necessary as a stencil buffer or alpha texture
48     * and sets the GrGpu's scissor and stencil state. If the return is false
49     * then the draw can be skipped. The AutoRestoreEffects is initialized by
50     * the manager when it must install additional effects to implement the
51     * clip. devBounds is optional but can help optimize clipping.
52     */
53    bool setupClipping(const GrClipData* clipDataIn, GrDrawState::AutoRestoreEffects*,
54                       const SkRect* devBounds);
55
56    /**
57     * Purge resources to free up memory. TODO: This class shouldn't hold any long lived refs
58     * which will allow ResourceCache2 to automatically purge anything this class has created.
59     */
60    void purgeResources();
61
62    bool isClipInStencil() const {
63        return kStencil_ClipMaskType == fCurrClipMaskType;
64    }
65    bool isClipInAlpha() const {
66        return kAlpha_ClipMaskType == fCurrClipMaskType;
67    }
68
69    void invalidateStencilMask() {
70        if (kStencil_ClipMaskType == fCurrClipMaskType) {
71            fCurrClipMaskType = kNone_ClipMaskType;
72        }
73    }
74
75    GrContext* getContext() {
76        return fAACache.getContext();
77    }
78
79    void setGpu(GrGpu* gpu);
80
81    void adjustPathStencilParams(GrStencilSettings* settings);
82private:
83    /**
84     * Informs the helper function adjustStencilParams() about how the stencil
85     * buffer clip is being used.
86     */
87    enum StencilClipMode {
88        // Draw to the clip bit of the stencil buffer
89        kModifyClip_StencilClipMode,
90        // Clip against the existing representation of the clip in the high bit
91        // of the stencil buffer.
92        kRespectClip_StencilClipMode,
93        // Neither writing to nor clipping against the clip bit.
94        kIgnoreClip_StencilClipMode,
95    };
96
97    GrGpu* fGpu;
98
99    /**
100     * We may represent the clip as a mask in the stencil buffer or as an alpha
101     * texture. It may be neither because the scissor rect suffices or we
102     * haven't yet examined the clip.
103     */
104    enum ClipMaskType {
105        kNone_ClipMaskType,
106        kStencil_ClipMaskType,
107        kAlpha_ClipMaskType,
108    } fCurrClipMaskType;
109
110    GrClipMaskCache fAACache;       // cache for the AA path
111
112    // Attempts to install a series of coverage effects to implement the clip. Return indicates
113    // whether the element list was successfully converted to effects.
114    bool installClipEffects(const GrReducedClip::ElementList&,
115                            GrDrawState::AutoRestoreEffects*,
116                            const SkVector& clipOffset,
117                            const SkRect* devBounds);
118
119    // Draws the clip into the stencil buffer
120    bool createStencilClipMask(int32_t elementsGenID,
121                               GrReducedClip::InitialState initialState,
122                               const GrReducedClip::ElementList& elements,
123                               const SkIRect& clipSpaceIBounds,
124                               const SkIPoint& clipSpaceToStencilOffset);
125    // Creates an alpha mask of the clip. The mask is a rasterization of elements through the
126    // rect specified by clipSpaceIBounds.
127    GrTexture* createAlphaClipMask(int32_t elementsGenID,
128                                   GrReducedClip::InitialState initialState,
129                                   const GrReducedClip::ElementList& elements,
130                                   const SkIRect& clipSpaceIBounds);
131    // Similar to createAlphaClipMask but it rasterizes in SW and uploads to the result texture.
132    GrTexture* createSoftwareClipMask(int32_t elementsGenID,
133                                      GrReducedClip::InitialState initialState,
134                                      const GrReducedClip::ElementList& elements,
135                                      const SkIRect& clipSpaceIBounds);
136
137    // Returns the cached mask texture if it matches the elementsGenID and the clipSpaceIBounds.
138    // Returns NULL if not found.
139    GrTexture* getCachedMaskTexture(int32_t elementsGenID, const SkIRect& clipSpaceIBounds);
140
141
142    // Handles allocation (if needed) of a clip alpha-mask texture for both the sw-upload
143    // or gpu-rendered cases.
144    GrTexture* allocMaskTexture(int32_t elementsGenID,
145                                const SkIRect& clipSpaceIBounds,
146                                bool willUpload);
147
148    bool useSWOnlyPath(const GrReducedClip::ElementList& elements);
149
150    // Draws a clip element into the target alpha mask. The caller should have already setup the
151    // desired blend operation. Optionally if the caller already selected a path renderer it can
152    // be passed. Otherwise the function will select one if the element is a path.
153    bool drawElement(GrTexture* target, const SkClipStack::Element*, GrPathRenderer* = NULL);
154
155    // Determines whether it is possible to draw the element to both the stencil buffer and the
156    // alpha mask simultaneously. If so and the element is a path a compatible path renderer is
157    // also returned.
158    bool canStencilAndDrawElement(GrTexture* target, const SkClipStack::Element*, GrPathRenderer**);
159
160    void mergeMask(GrTexture* dstMask,
161                   GrTexture* srcMask,
162                   SkRegion::Op op,
163                   const SkIRect& dstBound,
164                   const SkIRect& srcBound);
165
166    GrTexture* createTempMask(int width, int height);
167
168    void setupCache(const SkClipStack& clip,
169                    const SkIRect& bounds);
170
171    /**
172     * Called prior to return control back the GrGpu in setupClipping. It
173     * updates the GrGpu with stencil settings that account stencil-based
174     * clipping.
175     */
176    void setGpuStencil();
177
178    /**
179     * Adjusts the stencil settings to account for interaction with stencil
180     * clipping.
181     */
182    void adjustStencilParams(GrStencilSettings* settings,
183                             StencilClipMode mode,
184                             int stencilBitCnt);
185
186    typedef SkNoncopyable INHERITED;
187};
188
189#endif // GrClipMaskManager_DEFINED
190