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 */
23enum 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 */
43class GrCoordTransform : SkNoncopyable {
44public:
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     */
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     */
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
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     */
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
118    GrCoordSet sourceCoords() const { return fSourceCoords; }
119    const SkMatrix& getMatrix() const { return fMatrix; }
120    bool reverseY() const { return fReverseY; }
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 */
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
132private:
133    GrCoordSet              fSourceCoords;
134    SkMatrix                fMatrix;
135    bool                    fReverseY;
136    GrSLPrecision           fPrecision;
137    typedef SkNoncopyable INHERITED;
138
139#ifdef SK_DEBUG
140public:
141    void setInProcessor() const { fInProcessor = true; }
142private:
143    mutable bool fInProcessor;
144#endif
145};
146
147#endif
148