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 GrCoordTransform_DEFINED
9 #define GrCoordTransform_DEFINED
10 
11 #include "GrProcessor.h"
12 #include "SkMatrix.h"
13 #include "GrTexture.h"
14 #include "GrTypes.h"
15 #include "GrShaderVar.h"
16 
17 /**
18  * Coordinates available to GrProcessor subclasses for requesting transformations. Transformed
19  * coordinates are made available in the the portion of fragment shader emitted by the effect.
20  *
21  * The precision of the shader var that interpolates the transformed coordinates can be specified.
22  */
23 enum GrCoordSet {
24     /**
25      * The user-space coordinates that map to the fragment being rendered. This is the space in
26      * which SkShader operates. It is usually the space in which geometry passed to SkCanvas is
27      * specified (before the view matrix is applied). However, some draw calls take explicit local
28      * coords that map onto the geometry (e.g. drawVertices, drawBitmapRectToRect).
29      */
30     kLocal_GrCoordSet,
31 
32     /**
33      * The device space position of the fragment being shaded.
34      */
35     kDevice_GrCoordSet,
36 };
37 
38 /**
39  * A class representing a linear transformation from one of the built-in coordinate sets (local or
40  * position). GrProcessors just define these transformations, and the framework does the rest of the
41  * work to make the transformed coordinates available in their fragment shader.
42  */
43 class GrCoordTransform : SkNoncopyable {
44 public:
GrCoordTransform()45     GrCoordTransform() : fSourceCoords(kLocal_GrCoordSet) { SkDEBUGCODE(fInProcessor = false); }
46 
47     /**
48      * Create a transformation that maps [0, 1] to a texture's boundaries. The precision is inferred
49      * from the texture size and filter. The texture origin also implies whether a y-reversal should
50      * be performed.
51      */
GrCoordTransform(GrCoordSet sourceCoords,const GrTexture * texture,GrTextureParams::FilterMode filter)52     GrCoordTransform(GrCoordSet sourceCoords,
53                      const GrTexture* texture,
54                      GrTextureParams::FilterMode filter) {
55         SkASSERT(texture);
56         SkDEBUGCODE(fInProcessor = false);
57         this->reset(sourceCoords, texture, filter);
58     }
59 
60     /**
61      * Create a transformation from a matrix. The precision is inferred from the texture size and
62      * filter. The texture origin also implies whether a y-reversal should be performed.
63      */
GrCoordTransform(GrCoordSet sourceCoords,const SkMatrix & m,const GrTexture * texture,GrTextureParams::FilterMode filter)64     GrCoordTransform(GrCoordSet sourceCoords, const SkMatrix& m,
65                      const GrTexture* texture, GrTextureParams::FilterMode filter) {
66         SkDEBUGCODE(fInProcessor = false);
67         SkASSERT(texture);
68         this->reset(sourceCoords, m, texture, filter);
69     }
70 
71     /**
72      * Create a transformation that applies the matrix to a coord set.
73      */
74     GrCoordTransform(GrCoordSet sourceCoords, const SkMatrix& m,
75                      GrSLPrecision precision = kDefault_GrSLPrecision) {
76         SkDEBUGCODE(fInProcessor = false);
77         this->reset(sourceCoords, m, precision);
78     }
79 
reset(GrCoordSet sourceCoords,const GrTexture * texture,GrTextureParams::FilterMode filter)80     void reset(GrCoordSet sourceCoords, const GrTexture* texture,
81                GrTextureParams::FilterMode filter) {
82         SkASSERT(!fInProcessor);
83         SkASSERT(texture);
84         this->reset(sourceCoords, MakeDivByTextureWHMatrix(texture), texture, filter);
85     }
86 
87     void reset(GrCoordSet, const SkMatrix&, const GrTexture*, GrTextureParams::FilterMode filter);
88     void reset(GrCoordSet sourceCoords, const SkMatrix& m,
89                GrSLPrecision precision = kDefault_GrSLPrecision);
90 
91     GrCoordTransform& operator= (const GrCoordTransform& that) {
92         SkASSERT(!fInProcessor);
93         fSourceCoords = that.fSourceCoords;
94         fMatrix = that.fMatrix;
95         fReverseY = that.fReverseY;
96         fPrecision = that.fPrecision;
97         return *this;
98     }
99 
100     /**
101      * Access the matrix for editing. Note, this must be done before adding the transform to an
102      * effect, since effects are immutable.
103      */
accessMatrix()104     SkMatrix* accessMatrix() {
105         SkASSERT(!fInProcessor);
106         return &fMatrix;
107     }
108 
109     bool operator==(const GrCoordTransform& that) const {
110         return fSourceCoords == that.fSourceCoords &&
111                fMatrix.cheapEqualTo(that.fMatrix) &&
112                fReverseY == that.fReverseY &&
113                fPrecision == that.fPrecision;
114     }
115 
116     bool operator!=(const GrCoordTransform& that) const { return !(*this == that); }
117 
sourceCoords()118     GrCoordSet sourceCoords() const { return fSourceCoords; }
getMatrix()119     const SkMatrix& getMatrix() const { return fMatrix; }
reverseY()120     bool reverseY() const { return fReverseY; }
precision()121     GrSLPrecision precision() const { return fPrecision; }
122 
123     /** Useful for effects that want to insert a texture matrix that is implied by the texture
124         dimensions */
MakeDivByTextureWHMatrix(const GrTexture * texture)125     static inline SkMatrix MakeDivByTextureWHMatrix(const GrTexture* texture) {
126         SkASSERT(texture);
127         SkMatrix mat;
128         (void)mat.setIDiv(texture->width(), texture->height());
129         return mat;
130     }
131 
132 private:
133     GrCoordSet              fSourceCoords;
134     SkMatrix                fMatrix;
135     bool                    fReverseY;
136     GrSLPrecision           fPrecision;
137     typedef SkNoncopyable INHERITED;
138 
139 #ifdef SK_DEBUG
140 public:
setInProcessor()141     void setInProcessor() const { fInProcessor = true; }
142 private:
143     mutable bool fInProcessor;
144 #endif
145 };
146 
147 #endif
148