1/*
2 * Copyright 2014 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#include "GrCoordTransform.h"
9#include "GrCaps.h"
10#include "GrContext.h"
11#include "GrGpu.h"
12
13void GrCoordTransform::reset(GrCoordSet sourceCoords, const SkMatrix& m, const GrTexture* texture,
14                             GrTextureParams::FilterMode filter) {
15    SkASSERT(texture);
16    SkASSERT(!fInProcessor);
17
18    fSourceCoords = sourceCoords;
19    fMatrix = m;
20    fReverseY = kBottomLeft_GrSurfaceOrigin == texture->origin();
21
22    // Always start at kDefault. Then if precisions differ we see if the precision needs to be
23    // increased. Our rule is that we want at least 4 subpixel values in the representation for
24    // coords between 0 to 1 when bi- or tri-lerping and 1 value when nearest filtering. Note that
25    // this still might not be enough when drawing with repeat or mirror-repeat modes but that case
26    // can be arbitrarily bad.
27    int subPixelThresh = filter > GrTextureParams::kNone_FilterMode ? 4 : 1;
28    fPrecision = kDefault_GrSLPrecision;
29    if (texture->getContext()) {
30        const GrShaderCaps* caps = texture->getContext()->caps()->shaderCaps();
31        if (caps->floatPrecisionVaries()) {
32            int maxD = SkTMax(texture->width(), texture->height());
33            const GrShaderCaps::PrecisionInfo* info;
34            info = &caps->getFloatShaderPrecisionInfo(kFragment_GrShaderType, fPrecision);
35            do {
36                SkASSERT(info->supported());
37                // Make sure there is at least 2 bits of subpixel precision in the range of
38                // texture coords from 0.5 to 1.0.
39                if ((2 << info->fBits) / maxD > subPixelThresh) {
40                    break;
41                }
42                if (kHigh_GrSLPrecision == fPrecision) {
43                    break;
44                }
45                GrSLPrecision nextP = static_cast<GrSLPrecision>(fPrecision + 1);
46                info = &caps->getFloatShaderPrecisionInfo(kFragment_GrShaderType, nextP);
47                if (!info->supported()) {
48                    break;
49                }
50                fPrecision = nextP;
51            } while (true);
52        }
53    }
54}
55
56void GrCoordTransform::reset(GrCoordSet sourceCoords,
57                             const SkMatrix& m,
58                             GrSLPrecision precision) {
59    SkASSERT(!fInProcessor);
60    fSourceCoords = sourceCoords;
61    fMatrix = m;
62    fReverseY = false;
63    fPrecision = precision;
64}
65