GrClipMaskManager.h revision 3fc6a2fdb260aa85ad724d575afede2c00db111b 
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 GrClipTarget;
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        : fCurrClipMaskType(kNone_ClipMaskType)
43        , fClipTarget(NULL)
44        , fClipMode(kIgnoreClip_StencilClipMode) {
45    }
46
47    // The state of the scissor is controlled by the clip manager, no one else should set
48    // Scissor state.  This should really be on Gpu itself.  We should revist this when GPU
49    // and drawtarget are separate
50    struct ScissorState {
51        ScissorState() : fEnabled(false) {}
52        void set(const SkIRect& rect) { fRect = rect; fEnabled = true; }
53        bool operator==(const ScissorState& other) const {
54            return fEnabled == other.fEnabled &&
55                    (false == fEnabled || fRect == other.fRect);
56        }
57        bool operator!=(const ScissorState& other) const { return !(*this == other); }
58        bool    fEnabled;
59        SkIRect fRect;
60    };
61
62    /**
63     * Creates a clip mask if necessary as a stencil buffer or alpha texture
64     * and sets the GrGpu's scissor and stencil state. If the return is false
65     * then the draw can be skipped. The AutoRestoreEffects is initialized by
66     * the manager when it must install additional effects to implement the
67     * clip. devBounds is optional but can help optimize clipping.
68     */
69    bool setupClipping(const GrClipData* clipDataIn,
70                       const SkRect* devBounds,
71                       GrDrawState::AutoRestoreEffects*,
72                       GrDrawState::AutoRestoreStencil*,
73                       ScissorState*);
74
75    /**
76     * Purge resources to free up memory. TODO: This class shouldn't hold any long lived refs
77     * which will allow ResourceCache2 to automatically purge anything this class has created.
78     */
79    void purgeResources();
80
81    bool isClipInStencil() const {
82        return kStencil_ClipMaskType == fCurrClipMaskType;
83    }
84    bool isClipInAlpha() const {
85        return kAlpha_ClipMaskType == fCurrClipMaskType;
86    }
87
88    GrContext* getContext() {
89        return fAACache.getContext();
90    }
91
92    void setClipTarget(GrClipTarget*);
93
94    void adjustPathStencilParams(GrStencilSettings*);
95
96private:
97    /**
98     * Informs the helper function adjustStencilParams() about how the stencil
99     * buffer clip is being used.
100     */
101    enum StencilClipMode {
102        // Draw to the clip bit of the stencil buffer
103        kModifyClip_StencilClipMode,
104        // Clip against the existing representation of the clip in the high bit
105        // of the stencil buffer.
106        kRespectClip_StencilClipMode,
107        // Neither writing to nor clipping against the clip bit.
108        kIgnoreClip_StencilClipMode,
109    };
110
111    // Attempts to install a series of coverage effects to implement the clip. Return indicates
112    // whether the element list was successfully converted to effects.
113    bool installClipEffects(const GrReducedClip::ElementList&,
114                            GrDrawState::AutoRestoreEffects*,
115                            const SkVector& clipOffset,
116                            const SkRect* devBounds);
117
118    // Draws the clip into the stencil buffer
119    bool createStencilClipMask(int32_t elementsGenID,
120                               GrReducedClip::InitialState initialState,
121                               const GrReducedClip::ElementList& elements,
122                               const SkIRect& clipSpaceIBounds,
123                               const SkIPoint& clipSpaceToStencilOffset);
124    // Creates an alpha mask of the clip. The mask is a rasterization of elements through the
125    // rect specified by clipSpaceIBounds.
126    GrTexture* createAlphaClipMask(int32_t elementsGenID,
127                                   GrReducedClip::InitialState initialState,
128                                   const GrReducedClip::ElementList& elements,
129                                   const SkIRect& clipSpaceIBounds);
130    // Similar to createAlphaClipMask but it rasterizes in SW and uploads to the result texture.
131    GrTexture* createSoftwareClipMask(int32_t elementsGenID,
132                                      GrReducedClip::InitialState initialState,
133                                      const GrReducedClip::ElementList& elements,
134                                      const SkIRect& clipSpaceIBounds);
135
136    // Returns the cached mask texture if it matches the elementsGenID and the clipSpaceIBounds.
137    // Returns NULL if not found.
138    GrTexture* getCachedMaskTexture(int32_t elementsGenID, const SkIRect& clipSpaceIBounds);
139
140
141    // Handles allocation (if needed) of a clip alpha-mask texture for both the sw-upload
142    // or gpu-rendered cases.
143    GrTexture* allocMaskTexture(int32_t elementsGenID,
144                                const SkIRect& clipSpaceIBounds,
145                                bool willUpload);
146
147    bool useSWOnlyPath(const GrReducedClip::ElementList& elements);
148
149    // Draws a clip element into the target alpha mask. The caller should have already setup the
150    // desired blend operation. Optionally if the caller already selected a path renderer it can
151    // be passed. Otherwise the function will select one if the element is a path.
152    bool drawElement(GrTexture* target, const SkClipStack::Element*, GrPathRenderer* = NULL);
153
154    // Determines whether it is possible to draw the element to both the stencil buffer and the
155    // alpha mask simultaneously. If so and the element is a path a compatible path renderer is
156    // also returned.
157    bool canStencilAndDrawElement(GrTexture* target, const SkClipStack::Element*, GrPathRenderer**);
158
159    void mergeMask(GrTexture* dstMask,
160                   GrTexture* srcMask,
161                   SkRegion::Op op,
162                   const SkIRect& dstBound,
163                   const SkIRect& srcBound);
164
165    GrTexture* createTempMask(int width, int height);
166
167    void setupCache(const SkClipStack& clip,
168                    const SkIRect& bounds);
169
170    /**
171     * Called prior to return control back the GrGpu in setupClipping. It
172     * updates the GrGpu with stencil settings that account stencil-based
173     * clipping.
174     */
175    void setDrawStateStencil(GrDrawState::AutoRestoreStencil* asr);
176
177    /**
178     * Adjusts the stencil settings to account for interaction with stencil
179     * clipping.
180     */
181    void adjustStencilParams(GrStencilSettings* settings,
182                             StencilClipMode mode,
183                             int stencilBitCnt);
184
185    /**
186     * We may represent the clip as a mask in the stencil buffer or as an alpha
187     * texture. It may be neither because the scissor rect suffices or we
188     * haven't yet examined the clip.
189     */
190    enum ClipMaskType {
191        kNone_ClipMaskType,
192        kStencil_ClipMaskType,
193        kAlpha_ClipMaskType,
194    } fCurrClipMaskType;
195
196    GrClipMaskCache fAACache;       // cache for the AA path
197    GrClipTarget*   fClipTarget;
198    StencilClipMode fClipMode;
199
200    typedef SkNoncopyable INHERITED;
201};
202
203#endif // GrClipMaskManager_DEFINED
204