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    void releaseResources();
57
58    bool isClipInStencil() const {
59        return kStencil_ClipMaskType == fCurrClipMaskType;
60    }
61    bool isClipInAlpha() const {
62        return kAlpha_ClipMaskType == fCurrClipMaskType;
63    }
64
65    void invalidateStencilMask() {
66        if (kStencil_ClipMaskType == fCurrClipMaskType) {
67            fCurrClipMaskType = kNone_ClipMaskType;
68        }
69    }
70
71    GrContext* getContext() {
72        return fAACache.getContext();
73    }
74
75    void setGpu(GrGpu* gpu);
76
77    void adjustPathStencilParams(GrStencilSettings* settings);
78private:
79    /**
80     * Informs the helper function adjustStencilParams() about how the stencil
81     * buffer clip is being used.
82     */
83    enum StencilClipMode {
84        // Draw to the clip bit of the stencil buffer
85        kModifyClip_StencilClipMode,
86        // Clip against the existing representation of the clip in the high bit
87        // of the stencil buffer.
88        kRespectClip_StencilClipMode,
89        // Neither writing to nor clipping against the clip bit.
90        kIgnoreClip_StencilClipMode,
91    };
92
93    GrGpu* fGpu;
94
95    /**
96     * We may represent the clip as a mask in the stencil buffer or as an alpha
97     * texture. It may be neither because the scissor rect suffices or we
98     * haven't yet examined the clip.
99     */
100    enum ClipMaskType {
101        kNone_ClipMaskType,
102        kStencil_ClipMaskType,
103        kAlpha_ClipMaskType,
104    } fCurrClipMaskType;
105
106    GrClipMaskCache fAACache;       // cache for the AA path
107
108    // Attempts to install a series of coverage effects to implement the clip. Return indicates
109    // whether the element list was successfully converted to effects.
110    bool installClipEffects(const GrReducedClip::ElementList&,
111                            GrDrawState::AutoRestoreEffects*,
112                            const SkVector& clipOffset,
113                            const SkRect* devBounds);
114
115    // Draws the clip into the stencil buffer
116    bool createStencilClipMask(int32_t elementsGenID,
117                               GrReducedClip::InitialState initialState,
118                               const GrReducedClip::ElementList& elements,
119                               const SkIRect& clipSpaceIBounds,
120                               const SkIPoint& clipSpaceToStencilOffset);
121    // Creates an alpha mask of the clip. The mask is a rasterization of elements through the
122    // rect specified by clipSpaceIBounds.
123    GrTexture* createAlphaClipMask(int32_t elementsGenID,
124                                   GrReducedClip::InitialState initialState,
125                                   const GrReducedClip::ElementList& elements,
126                                   const SkIRect& clipSpaceIBounds);
127    // Similar to createAlphaClipMask but it rasterizes in SW and uploads to the result texture.
128    GrTexture* createSoftwareClipMask(int32_t elementsGenID,
129                                      GrReducedClip::InitialState initialState,
130                                      const GrReducedClip::ElementList& elements,
131                                      const SkIRect& clipSpaceIBounds);
132
133    // Returns the cached mask texture if it matches the elementsGenID and the clipSpaceIBounds.
134    // Returns NULL if not found.
135    GrTexture* getCachedMaskTexture(int32_t elementsGenID, const SkIRect& clipSpaceIBounds);
136
137
138    // Handles allocation (if needed) of a clip alpha-mask texture for both the sw-upload
139    // or gpu-rendered cases.
140    GrTexture* allocMaskTexture(int32_t elementsGenID,
141                                const SkIRect& clipSpaceIBounds,
142                                bool willUpload);
143
144    bool useSWOnlyPath(const GrReducedClip::ElementList& elements);
145
146    // Draws a clip element into the target alpha mask. The caller should have already setup the
147    // desired blend operation. Optionally if the caller already selected a path renderer it can
148    // be passed. Otherwise the function will select one if the element is a path.
149    bool drawElement(GrTexture* target, const SkClipStack::Element*, GrPathRenderer* = NULL);
150
151    // Determines whether it is possible to draw the element to both the stencil buffer and the
152    // alpha mask simultaneously. If so and the element is a path a compatible path renderer is
153    // also returned.
154    bool canStencilAndDrawElement(GrTexture* target, const SkClipStack::Element*, GrPathRenderer**);
155
156    void mergeMask(GrTexture* dstMask,
157                   GrTexture* srcMask,
158                   SkRegion::Op op,
159                   const SkIRect& dstBound,
160                   const SkIRect& srcBound);
161
162    void getTemp(int width, int height, GrAutoScratchTexture* temp);
163
164    void setupCache(const SkClipStack& clip,
165                    const SkIRect& bounds);
166
167    /**
168     * Called prior to return control back the GrGpu in setupClipping. It
169     * updates the GrGpu with stencil settings that account stencil-based
170     * clipping.
171     */
172    void setGpuStencil();
173
174    /**
175     * Adjusts the stencil settings to account for interaction with stencil
176     * clipping.
177     */
178    void adjustStencilParams(GrStencilSettings* settings,
179                             StencilClipMode mode,
180                             int stencilBitCnt);
181
182    typedef SkNoncopyable INHERITED;
183};
184
185#endif // GrClipMaskManager_DEFINED
186