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      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 
     25 class GrGpu;
     26 class GrPathRenderer;
     27 class GrPathRendererChain;
     28 class GrTexture;
     29 class 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  */
     39 class GrClipMaskManager : public SkNoncopyable {
     40 public:
     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);
     75 private:
     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