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 : public 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.
50     */
51    bool setupClipping(const GrClipData* clipDataIn, GrDrawState::AutoRestoreEffects*);
52
53    void releaseResources();
54
55    bool isClipInStencil() const {
56        return kStencil_ClipMaskType == fCurrClipMaskType;
57    }
58    bool isClipInAlpha() const {
59        return kAlpha_ClipMaskType == fCurrClipMaskType;
60    }
61
62    void invalidateStencilMask() {
63        if (kStencil_ClipMaskType == fCurrClipMaskType) {
64            fCurrClipMaskType = kNone_ClipMaskType;
65        }
66    }
67
68    GrContext* getContext() {
69        return fAACache.getContext();
70    }
71
72    void setGpu(GrGpu* gpu);
73
74    void adjustPathStencilParams(GrStencilSettings* settings);
75private:
76    /**
77     * Informs the helper function adjustStencilParams() about how the stencil
78     * buffer clip is being used.
79     */
80    enum StencilClipMode {
81        // Draw to the clip bit of the stencil buffer
82        kModifyClip_StencilClipMode,
83        // Clip against the existing representation of the clip in the high bit
84        // of the stencil buffer.
85        kRespectClip_StencilClipMode,
86        // Neither writing to nor clipping against the clip bit.
87        kIgnoreClip_StencilClipMode,
88    };
89
90    GrGpu* fGpu;
91
92    /**
93     * We may represent the clip as a mask in the stencil buffer or as an alpha
94     * texture. It may be neither because the scissor rect suffices or we
95     * haven't yet examined the clip.
96     */
97    enum ClipMaskType {
98        kNone_ClipMaskType,
99        kStencil_ClipMaskType,
100        kAlpha_ClipMaskType,
101    } fCurrClipMaskType;
102
103    GrClipMaskCache fAACache;       // cache for the AA path
104
105    // Draws the clip into the stencil buffer
106    bool createStencilClipMask(int32_t elementsGenID,
107                               GrReducedClip::InitialState initialState,
108                               const GrReducedClip::ElementList& elements,
109                               const SkIRect& clipSpaceIBounds,
110                               const SkIPoint& clipSpaceToStencilOffset);
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 SkIRect& clipSpaceIBounds);
117    // Similar to createAlphaClipMask but it rasterizes in SW and uploads to the result texture.
118    GrTexture* createSoftwareClipMask(int32_t elementsGenID,
119                                      GrReducedClip::InitialState initialState,
120                                      const GrReducedClip::ElementList& elements,
121                                      const SkIRect& clipSpaceIBounds);
122
123    // Gets a texture to use for the clip mask. If true is returned then a cached mask was found
124    // that already contains the rasterization of the clip stack, otherwise an uninitialized texture
125    // is returned. 'willUpload' is set when the alpha mask needs to be uploaded from the CPU.
126    bool getMaskTexture(int32_t elementsGenID,
127                        const SkIRect& clipSpaceIBounds,
128                        GrTexture** result,
129                        bool willUpload);
130
131    bool useSWOnlyPath(const GrReducedClip::ElementList& elements);
132
133    // Draws a clip element into the target alpha mask. The caller should have already setup the
134    // desired blend operation. Optionally if the caller already selected a path renderer it can
135    // be passed. Otherwise the function will select one if the element is a path.
136    bool drawElement(GrTexture* target, const SkClipStack::Element*, GrPathRenderer* = NULL);
137
138    // Determines whether it is possible to draw the element to both the stencil buffer and the
139    // alpha mask simultaneously. If so and the element is a path a compatible path renderer is
140    // also returned.
141    bool canStencilAndDrawElement(GrTexture* target, const SkClipStack::Element*, GrPathRenderer**);
142
143    void mergeMask(GrTexture* dstMask,
144                   GrTexture* srcMask,
145                   SkRegion::Op op,
146                   const SkIRect& dstBound,
147                   const SkIRect& srcBound);
148
149    void getTemp(int width, int height, GrAutoScratchTexture* temp);
150
151    void setupCache(const SkClipStack& clip,
152                    const SkIRect& bounds);
153
154    /**
155     * Called prior to return control back the GrGpu in setupClipping. It
156     * updates the GrGpu with stencil settings that account stencil-based
157     * clipping.
158     */
159    void setGpuStencil();
160
161    /**
162     * Adjusts the stencil settings to account for interaction with stencil
163     * clipping.
164     */
165    void adjustStencilParams(GrStencilSettings* settings,
166                             StencilClipMode mode,
167                             int stencilBitCnt);
168
169    typedef SkNoncopyable INHERITED;
170};
171
172#endif // GrClipMaskManager_DEFINED
173