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      1 /*
      2  * Copyright 2013 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 GrGeometryProcessor_DEFINED
      9 #define GrGeometryProcessor_DEFINED
     10 
     11 #include "GrPrimitiveProcessor.h"
     12 
     13 /**
     14  * A GrGeometryProcessor is a flexible method for rendering a primitive.  The GrGeometryProcessor
     15  * has complete control over vertex attributes and uniforms(aside from the render target) but it
     16  * must obey the same contract as any GrPrimitiveProcessor, specifically it must emit a color and
     17  * coverage into the fragment shader.  Where this color and coverage come from is completely the
     18  * responsibility of the GrGeometryProcessor.
     19  */
     20 class GrGeometryProcessor : public GrPrimitiveProcessor {
     21 public:
     22     GrGeometryProcessor()
     23         : fWillUseGeoShader(false)
     24         , fLocalCoordsType(kUnused_LocalCoordsType) {}
     25 
     26     bool willUseGeoShader() const override { return fWillUseGeoShader; }
     27 
     28     bool hasTransformedLocalCoords() const override {
     29         return kHasTransformed_LocalCoordsType == fLocalCoordsType;
     30     }
     31 
     32     bool hasExplicitLocalCoords() const override {
     33         return kHasExplicit_LocalCoordsType == fLocalCoordsType;
     34     }
     35 
     36 protected:
     37     /**
     38      * Subclasses call this from their constructor to register vertex attributes.  Attributes
     39      * will be padded to the nearest 4 bytes for performance reasons.
     40      * TODO After deferred geometry, we should do all of this inline in GenerateGeometry alongside
     41      * the struct used to actually populate the attributes.  This is all extremely fragile, vertex
     42      * attributes have to be added in the order they will appear in the struct which maps memory.
     43      * The processor key should reflect the vertex attributes, or there lack thereof in the
     44      * GrGeometryProcessor.
     45      */
     46     const Attribute& addVertexAttrib(const Attribute& attribute) {
     47         SkASSERT(fNumAttribs < kMaxVertexAttribs);
     48         fVertexStride += attribute.fOffset;
     49         fAttribs[fNumAttribs] = attribute;
     50         return fAttribs[fNumAttribs++];
     51     }
     52 
     53     void setWillUseGeoShader() { fWillUseGeoShader = true; }
     54 
     55     /**
     56      * If a GrFragmentProcessor in the GrPipeline needs localCoods, we will provide them in one of
     57      * three ways
     58      * 1) LocalCoordTransform * Position - in Shader
     59      * 2) LocalCoordTransform * ExplicitLocalCoords- in Shader
     60      * 3) A transformation on the CPU uploaded via vertex attribute
     61      * TODO make this GrBatches responsibility
     62      */
     63     enum LocalCoordsType {
     64         kUnused_LocalCoordsType,
     65         kHasExplicit_LocalCoordsType,
     66         kHasTransformed_LocalCoordsType
     67     };
     68 
     69     void setHasExplicitLocalCoords() {
     70         SkASSERT(kUnused_LocalCoordsType == fLocalCoordsType);
     71         fLocalCoordsType = kHasExplicit_LocalCoordsType;
     72     }
     73     void setHasTransformedLocalCoords() {
     74         SkASSERT(kUnused_LocalCoordsType == fLocalCoordsType);
     75         fLocalCoordsType = kHasTransformed_LocalCoordsType;
     76     }
     77 
     78 private:
     79     bool fWillUseGeoShader;
     80     LocalCoordsType fLocalCoordsType;
     81 
     82     typedef GrPrimitiveProcessor INHERITED;
     83 };
     84 
     85 #endif
     86