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      1 /*
      2  * Copyright 2011 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 GrRenderTarget_DEFINED
      9 #define GrRenderTarget_DEFINED
     10 
     11 #include "GrSurface.h"
     12 #include "SkRect.h"
     13 
     14 class GrStencilAttachment;
     15 class GrRenderTargetPriv;
     16 
     17 /**
     18  * GrRenderTarget represents a 2D buffer of pixels that can be rendered to.
     19  * A context's render target is set by setRenderTarget(). Render targets are
     20  * created by a createTexture with the kRenderTarget_SurfaceFlag flag.
     21  * Additionally, GrContext provides methods for creating GrRenderTargets
     22  * that wrap externally created render targets.
     23  */
     24 class GrRenderTarget : virtual public GrSurface {
     25 public:
     26     SK_DECLARE_INST_COUNT(GrRenderTarget)
     27 
     28     // GrSurface overrides
     29     GrRenderTarget* asRenderTarget() override { return this; }
     30     const GrRenderTarget* asRenderTarget() const  override { return this; }
     31 
     32     // GrRenderTarget
     33     /**
     34      * @return true if the surface is multisampled, false otherwise
     35      */
     36     bool isMultisampled() const { return 0 != fDesc.fSampleCnt; }
     37 
     38     /**
     39      * @return the number of samples-per-pixel or zero if non-MSAA.
     40      */
     41     int numSamples() const { return fDesc.fSampleCnt; }
     42 
     43     /**
     44      * Call to indicate the multisample contents were modified such that the
     45      * render target needs to be resolved before it can be used as texture. Gr
     46      * tracks this for its own drawing and thus this only needs to be called
     47      * when the render target has been modified outside of Gr. This has no
     48      * effect on wrapped backend render targets.
     49      *
     50      * @param rect  a rect bounding the area needing resolve. NULL indicates
     51      *              the whole RT needs resolving.
     52      */
     53     void flagAsNeedingResolve(const SkIRect* rect = NULL);
     54 
     55     /**
     56      * Call to override the region that needs to be resolved.
     57      */
     58     void overrideResolveRect(const SkIRect rect);
     59 
     60     /**
     61      * Call to indicate that GrRenderTarget was externally resolved. This may
     62      * allow Gr to skip a redundant resolve step.
     63      */
     64     void flagAsResolved() { fResolveRect.setLargestInverted(); }
     65 
     66     /**
     67      * @return true if the GrRenderTarget requires MSAA resolving
     68      */
     69     bool needsResolve() const { return !fResolveRect.isEmpty(); }
     70 
     71     /**
     72      * Returns a rect bounding the region needing resolving.
     73      */
     74     const SkIRect& getResolveRect() const { return fResolveRect; }
     75 
     76     /**
     77      * Provide a performance hint that the render target's contents are allowed
     78      * to become undefined.
     79      */
     80     void discard();
     81 
     82     // a MSAA RT may require explicit resolving , it may auto-resolve (e.g. FBO
     83     // 0 in GL), or be unresolvable because the client didn't give us the
     84     // resolve destination.
     85     enum ResolveType {
     86         kCanResolve_ResolveType,
     87         kAutoResolves_ResolveType,
     88         kCantResolve_ResolveType,
     89     };
     90     virtual ResolveType getResolveType() const = 0;
     91 
     92     // Provides access to functions that aren't part of the public API.
     93     GrRenderTargetPriv renderTargetPriv();
     94     const GrRenderTargetPriv renderTargetPriv() const;
     95 
     96 protected:
     97     GrRenderTarget(GrGpu* gpu, LifeCycle lifeCycle, const GrSurfaceDesc& desc)
     98         : INHERITED(gpu, lifeCycle, desc)
     99         , fStencilAttachment(NULL) {
    100         fResolveRect.setLargestInverted();
    101     }
    102 
    103     // override of GrResource
    104     void onAbandon() override;
    105     void onRelease() override;
    106 
    107 private:
    108     // Checked when this object is asked to attach a stencil buffer.
    109     virtual bool canAttemptStencilAttachment() const = 0;
    110 
    111     friend class GrRenderTargetPriv;
    112 
    113     GrStencilAttachment*  fStencilAttachment;
    114 
    115     SkIRect               fResolveRect;
    116 
    117     typedef GrSurface INHERITED;
    118 };
    119 
    120 #endif
    121