Blend.cpp revision 260ab726486317496bc12a57d599ea96dcde3284 
1/*
2 * Copyright (C) 2015 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 *      http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16#include <renderstate/Blend.h>
17#include "Program.h"
18
19#include "ShadowTessellator.h"
20
21namespace android {
22namespace uirenderer {
23
24/**
25 * Structure mapping Skia xfermodes to OpenGL blending factors.
26 */
27struct Blender {
28    SkBlendMode mode;
29    GLenum src;
30    GLenum dst;
31};
32
33// assumptions made by lookup tables in either this file or ProgramCache
34static_assert(0 == static_cast<int>(SkBlendMode::kClear), "SkBlendMode enums have changed");
35static_assert(1 == static_cast<int>(SkBlendMode::kSrc), "SkBlendMode enums have changed");
36static_assert(2 == static_cast<int>(SkBlendMode::kDst), "SkBlendMode enums have changed");
37static_assert(3 == static_cast<int>(SkBlendMode::kSrcOver), "SkBlendMode enums have changed");
38static_assert(4 == static_cast<int>(SkBlendMode::kDstOver), "SkBlendMode enums have changed");
39static_assert(5 == static_cast<int>(SkBlendMode::kSrcIn), "SkBlendMode enums have changed");
40static_assert(6 == static_cast<int>(SkBlendMode::kDstIn), "SkBlendMode enums have changed");
41static_assert(7 == static_cast<int>(SkBlendMode::kSrcOut), "SkBlendMode enums have changed");
42static_assert(8 == static_cast<int>(SkBlendMode::kDstOut), "SkBlendMode enums have changed");
43static_assert(9 == static_cast<int>(SkBlendMode::kSrcATop), "SkBlendMode enums have changed");
44static_assert(10 == static_cast<int>(SkBlendMode::kDstATop), "SkBlendMode enums have changed");
45static_assert(11 == static_cast<int>(SkBlendMode::kXor), "SkBlendMode enums have changed");
46static_assert(12 == static_cast<int>(SkBlendMode::kPlus), "SkBlendMode enums have changed");
47static_assert(13 == static_cast<int>(SkBlendMode::kModulate), "SkBlendMode enums have changed");
48static_assert(14 == static_cast<int>(SkBlendMode::kScreen), "SkBlendMode enums have changed");
49static_assert(15 == static_cast<int>(SkBlendMode::kOverlay), "SkBlendMode enums have changed");
50static_assert(16 == static_cast<int>(SkBlendMode::kDarken), "SkBlendMode enums have changed");
51static_assert(17 == static_cast<int>(SkBlendMode::kLighten), "SkBlendMode enums have changed");
52
53// In this array, the index of each Blender equals the value of the first
54// entry. For instance, gBlends[1] == gBlends[SkBlendMode::kSrc]
55const Blender kBlends[] = {
56    { SkBlendMode::kClear,    GL_ZERO,                GL_ONE_MINUS_SRC_ALPHA },
57    { SkBlendMode::kSrc,      GL_ONE,                 GL_ZERO },
58    { SkBlendMode::kDst,      GL_ZERO,                GL_ONE },
59    { SkBlendMode::kSrcOver,  GL_ONE,                 GL_ONE_MINUS_SRC_ALPHA },
60    { SkBlendMode::kDstOver,  GL_ONE_MINUS_DST_ALPHA, GL_ONE },
61    { SkBlendMode::kSrcIn,    GL_DST_ALPHA,           GL_ZERO },
62    { SkBlendMode::kDstIn,    GL_ZERO,                GL_SRC_ALPHA },
63    { SkBlendMode::kSrcOut,   GL_ONE_MINUS_DST_ALPHA, GL_ZERO },
64    { SkBlendMode::kDstOut,   GL_ZERO,                GL_ONE_MINUS_SRC_ALPHA },
65    { SkBlendMode::kSrcATop,  GL_DST_ALPHA,           GL_ONE_MINUS_SRC_ALPHA },
66    { SkBlendMode::kDstATop,  GL_ONE_MINUS_DST_ALPHA, GL_SRC_ALPHA },
67    { SkBlendMode::kXor,      GL_ONE_MINUS_DST_ALPHA, GL_ONE_MINUS_SRC_ALPHA },
68    { SkBlendMode::kPlus,     GL_ONE,                 GL_ONE },
69    { SkBlendMode::kModulate, GL_ZERO,                GL_SRC_COLOR },
70    { SkBlendMode::kScreen,   GL_ONE,                 GL_ONE_MINUS_SRC_COLOR }
71};
72
73// This array contains the swapped version of each SkBlendMode. For instance
74// this array's SrcOver blending mode is actually DstOver. You can refer to
75// createLayer() for more information on the purpose of this array.
76const Blender kBlendsSwap[] = {
77    { SkBlendMode::kClear,    GL_ONE_MINUS_DST_ALPHA, GL_ZERO },
78    { SkBlendMode::kSrc,      GL_ZERO,                GL_ONE },
79    { SkBlendMode::kDst,      GL_ONE,                 GL_ZERO },
80    { SkBlendMode::kSrcOver,  GL_ONE_MINUS_DST_ALPHA, GL_ONE },
81    { SkBlendMode::kDstOver,  GL_ONE,                 GL_ONE_MINUS_SRC_ALPHA },
82    { SkBlendMode::kSrcIn,    GL_ZERO,                GL_SRC_ALPHA },
83    { SkBlendMode::kDstIn,    GL_DST_ALPHA,           GL_ZERO },
84    { SkBlendMode::kSrcOut,   GL_ZERO,                GL_ONE_MINUS_SRC_ALPHA },
85    { SkBlendMode::kDstOut,   GL_ONE_MINUS_DST_ALPHA, GL_ZERO },
86    { SkBlendMode::kSrcATop,  GL_ONE_MINUS_DST_ALPHA, GL_SRC_ALPHA },
87    { SkBlendMode::kDstATop,  GL_DST_ALPHA,           GL_ONE_MINUS_SRC_ALPHA },
88    { SkBlendMode::kXor,      GL_ONE_MINUS_DST_ALPHA, GL_ONE_MINUS_SRC_ALPHA },
89    { SkBlendMode::kPlus,     GL_ONE,                 GL_ONE },
90    { SkBlendMode::kModulate, GL_DST_COLOR,           GL_ZERO },
91    { SkBlendMode::kScreen,   GL_ONE_MINUS_DST_COLOR, GL_ONE }
92};
93
94Blend::Blend()
95    : mEnabled(false)
96    , mSrcMode(GL_ZERO)
97    , mDstMode(GL_ZERO) {
98    // gl blending off by default
99}
100
101void Blend::invalidate() {
102    syncEnabled();
103    mSrcMode = mDstMode = GL_ZERO;
104}
105
106void Blend::syncEnabled() {
107    if (mEnabled) {
108        glEnable(GL_BLEND);
109    } else {
110        glDisable(GL_BLEND);
111    }
112}
113
114void Blend::getFactors(SkBlendMode mode, ModeOrderSwap modeUsage, GLenum* outSrc, GLenum* outDst) {
115    int index = static_cast<int>(mode);
116    *outSrc = (modeUsage == ModeOrderSwap::Swap) ? kBlendsSwap[index].src : kBlends[index].src;
117    *outDst = (modeUsage == ModeOrderSwap::Swap) ? kBlendsSwap[index].dst : kBlends[index].dst;
118}
119
120void Blend::setFactors(GLenum srcMode, GLenum dstMode) {
121    if (srcMode == GL_ZERO && dstMode == GL_ZERO) {
122        // disable blending
123        if (mEnabled) {
124            glDisable(GL_BLEND);
125            mEnabled = false;
126        }
127    } else {
128        // enable blending
129        if (!mEnabled) {
130            glEnable(GL_BLEND);
131            mEnabled = true;
132        }
133
134        if (srcMode != mSrcMode || dstMode != mDstMode) {
135            glBlendFunc(srcMode, dstMode);
136            mSrcMode = srcMode;
137            mDstMode = dstMode;
138        }
139    }
140}
141
142void Blend::dump() {
143    ALOGD("Blend: enabled %d, func src %d, dst %d", mEnabled, mSrcMode, mDstMode);
144}
145
146} /* namespace uirenderer */
147} /* namespace android */
148
149