GrSingleTextureEffect.h revision f8449babdc430bb522c0eb87ce18f05c54d83714 
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 GrSingleTextureEffect_DEFINED
9#define GrSingleTextureEffect_DEFINED
10
11#include "GrFragmentProcessor.h"
12#include "GrCoordTransform.h"
13#include "GrInvariantOutput.h"
14#include "SkMatrix.h"
15
16class GrTexture;
17
18/**
19 * A base class for effects that draw a single texture with a texture matrix. This effect has no
20 * backend implementations. One must be provided by the subclass.
21 */
22class GrSingleTextureEffect : public GrFragmentProcessor {
23public:
24    virtual ~GrSingleTextureEffect();
25
26protected:
27    /** unfiltered, clamp mode */
28    GrSingleTextureEffect(GrTexture*, const SkMatrix&, GrCoordSet = kLocal_GrCoordSet);
29    /** clamp mode */
30    GrSingleTextureEffect(GrTexture*, const SkMatrix&, GrTextureParams::FilterMode filterMode,
31                          GrCoordSet = kLocal_GrCoordSet);
32    GrSingleTextureEffect(GrTexture*,
33                          const SkMatrix&,
34                          const GrTextureParams&,
35                          GrCoordSet = kLocal_GrCoordSet);
36
37    /**
38     * Can be used as a helper to implement subclass onComputeInvariantOutput(). It assumes that
39     * the subclass output color will be a modulation of the input color with a value read from the
40     * texture.
41     */
42    void updateInvariantOutputForModulation(GrInvariantOutput* inout) const {
43        if (GrPixelConfigIsAlphaOnly(this->texture(0)->config())) {
44            inout->mulByUnknownAlpha();
45        } else if (GrPixelConfigIsOpaque(this->texture(0)->config())) {
46            inout->mulByUnknownOpaqueColor();
47        } else {
48            inout->mulByUnknownColor();
49        }
50    }
51
52private:
53    GrCoordTransform fCoordTransform;
54    GrTextureAccess  fTextureAccess;
55
56    typedef GrFragmentProcessor INHERITED;
57};
58
59#endif
60