GrClipMaskManager.h revision 8059eb9f6e24ed609393fbda4ad71edea03ac258 
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#ifndef GrClipMaskManager_DEFINED
8#define GrClipMaskManager_DEFINED
9
10#include "GrClipMaskCache.h"
11#include "GrContext.h"
12#include "GrDrawState.h"
13#include "GrReducedClip.h"
14#include "GrStencil.h"
15#include "GrTexture.h"
16#include "SkClipStack.h"
17#include "SkDeque.h"
18#include "SkPath.h"
19#include "SkRefCnt.h"
20#include "SkTLList.h"
21#include "SkTypes.h"
22
23class GrClipTarget;
24class GrPathRenderer;
25class GrPathRendererChain;
26class GrTexture;
27class SkPath;
28/**
29 * The clip mask creator handles the generation of the clip mask. If anti
30 * aliasing is requested it will (in the future) generate a single channel
31 * (8bit) mask. If no anti aliasing is requested it will generate a 1-bit
32 * mask in the stencil buffer. In the non anti-aliasing case, if the clip
33 * mask can be represented as a rectangle then scissoring is used. In all
34 * cases scissoring is used to bound the range of the clip mask.
35 */
36class GrClipMaskManager : SkNoncopyable {
37public:
38    GrClipMaskManager()
39        : fCurrClipMaskType(kNone_ClipMaskType)
40        , fClipTarget(NULL)
41        , fClipMode(kIgnoreClip_StencilClipMode) {
42    }
43
44    /**
45     * Creates a clip mask if necessary as a stencil buffer or alpha texture
46     * and sets the GrGpu's scissor and stencil state. If the return is false
47     * then the draw can be skipped. The AutoRestoreEffects is initialized by
48     * the manager when it must install additional effects to implement the
49     * clip. devBounds is optional but can help optimize clipping.
50     */
51    bool setupClipping(GrDrawState*,
52                       GrDrawState::AutoRestoreEffects*,
53                       GrDrawState::AutoRestoreStencil*,
54                       GrScissorState*,
55                       const GrClipData* clipDataIn,
56                       const SkRect* devBounds);
57
58    /**
59     * Purge resources to free up memory. TODO: This class shouldn't hold any long lived refs
60     * which will allow ResourceCache2 to automatically purge anything this class has created.
61     */
62    void purgeResources();
63
64    bool isClipInStencil() const {
65        return kStencil_ClipMaskType == fCurrClipMaskType;
66    }
67
68    bool isClipInAlpha() const {
69        return kAlpha_ClipMaskType == fCurrClipMaskType;
70    }
71
72    GrContext* getContext() {
73        return fAACache.getContext();
74    }
75
76    void setClipTarget(GrClipTarget*);
77
78    void adjustPathStencilParams(const GrStencilBuffer*, GrStencilSettings*);
79
80private:
81    /**
82     * Informs the helper function adjustStencilParams() about how the stencil
83     * buffer clip is being used.
84     */
85    enum StencilClipMode {
86        // Draw to the clip bit of the stencil buffer
87        kModifyClip_StencilClipMode,
88        // Clip against the existing representation of the clip in the high bit
89        // of the stencil buffer.
90        kRespectClip_StencilClipMode,
91        // Neither writing to nor clipping against the clip bit.
92        kIgnoreClip_StencilClipMode,
93    };
94
95    // Attempts to install a series of coverage effects to implement the clip. Return indicates
96    // whether the element list was successfully converted to effects.
97    bool installClipEffects(GrDrawState*,
98                            GrDrawState::AutoRestoreEffects*,
99                            const GrReducedClip::ElementList&,
100                            const SkVector& clipOffset,
101                            const SkRect* devBounds);
102
103    // Draws the clip into the stencil buffer
104    bool createStencilClipMask(GrRenderTarget*,
105                               int32_t elementsGenID,
106                               GrReducedClip::InitialState initialState,
107                               const GrReducedClip::ElementList& elements,
108                               const SkIRect& clipSpaceIBounds,
109                               const SkIPoint& clipSpaceToStencilOffset);
110
111    // Creates an alpha mask of the clip. The mask is a rasterization of elements through the
112    // rect specified by clipSpaceIBounds.
113    GrTexture* createAlphaClipMask(int32_t elementsGenID,
114                                   GrReducedClip::InitialState initialState,
115                                   const GrReducedClip::ElementList& elements,
116                                   const SkVector& clipToMaskOffset,
117                                   const SkIRect& clipSpaceIBounds);
118
119    // Similar to createAlphaClipMask but it rasterizes in SW and uploads to the result texture.
120    GrTexture* createSoftwareClipMask(int32_t elementsGenID,
121                                      GrReducedClip::InitialState initialState,
122                                      const GrReducedClip::ElementList& elements,
123                                      const SkVector& clipToMaskOffset,
124                                      const SkIRect& clipSpaceIBounds);
125
126    // Returns the cached mask texture if it matches the elementsGenID and the clipSpaceIBounds.
127    // Returns NULL if not found.
128    GrTexture* getCachedMaskTexture(int32_t elementsGenID, const SkIRect& clipSpaceIBounds);
129
130    // Handles allocation (if needed) of a clip alpha-mask texture for both the sw-upload
131    // or gpu-rendered cases.
132    GrTexture* allocMaskTexture(int32_t elementsGenID,
133                                const SkIRect& clipSpaceIBounds,
134                                bool willUpload);
135
136    bool useSWOnlyPath(const GrDrawState*,
137                       const SkVector& clipToMaskOffset,
138                       const GrReducedClip::ElementList& elements);
139
140    // Draws a clip element into the target alpha mask. The caller should have already setup the
141    // desired blend operation. Optionally if the caller already selected a path renderer it can
142    // be passed. Otherwise the function will select one if the element is a path.
143    bool drawElement(GrDrawState*,
144                     const SkMatrix& viewMatrix,
145                     GrTexture* target,
146                     const SkClipStack::Element*,
147                     GrPathRenderer* pr = NULL);
148
149    // Determines whether it is possible to draw the element to both the stencil buffer and the
150    // alpha mask simultaneously. If so and the element is a path a compatible path renderer is
151    // also returned.
152    bool canStencilAndDrawElement(GrDrawState*,
153                                  GrTexture* target,
154                                  GrPathRenderer**,
155                                  const SkClipStack::Element*);
156
157    void mergeMask(GrDrawState*,
158                   GrTexture* dstMask,
159                   GrTexture* srcMask,
160                   SkRegion::Op op,
161                   const SkIRect& dstBound,
162                   const SkIRect& srcBound);
163
164    GrTexture* createTempMask(int width, int height);
165
166    void setupCache(const SkClipStack& clip,
167                    const SkIRect& bounds);
168    /**
169     * Called prior to return control back the GrGpu in setupClipping. It
170     * updates the GrGpu with stencil settings that account stencil-based
171     * clipping.
172     */
173    void setDrawStateStencil(GrDrawState*, GrDrawState::AutoRestoreStencil*);
174
175    /**
176     * Adjusts the stencil settings to account for interaction with stencil
177     * clipping.
178     */
179    void adjustStencilParams(GrStencilSettings* settings,
180                             StencilClipMode mode,
181                             int stencilBitCnt);
182
183    /**
184     * We may represent the clip as a mask in the stencil buffer or as an alpha
185     * texture. It may be neither because the scissor rect suffices or we
186     * haven't yet examined the clip.
187     */
188    enum ClipMaskType {
189        kNone_ClipMaskType,
190        kStencil_ClipMaskType,
191        kAlpha_ClipMaskType,
192    } fCurrClipMaskType;
193
194    GrClipMaskCache fAACache;       // cache for the AA path
195    GrClipTarget*   fClipTarget;
196    StencilClipMode fClipMode;
197
198    typedef SkNoncopyable INHERITED;
199};
200#endif // GrClipMaskManager_DEFINED
201