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/*
* Copyright (C) 2015 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include <renderstate/Blend.h>
#include "Program.h"
#include "ShadowTessellator.h"
namespace android {
namespace uirenderer {
/**
* Structure mapping Skia xfermodes to OpenGL blending factors.
*/
struct Blender {
SkXfermode::Mode mode;
GLenum src;
GLenum dst;
};
// In this array, the index of each Blender equals the value of the first
// entry. For instance, gBlends[1] == gBlends[SkXfermode::kSrc_Mode]
const Blender kBlends[] = {
{ SkXfermode::kClear_Mode, GL_ZERO, GL_ONE_MINUS_SRC_ALPHA },
{ SkXfermode::kSrc_Mode, GL_ONE, GL_ZERO },
{ SkXfermode::kDst_Mode, GL_ZERO, GL_ONE },
{ SkXfermode::kSrcOver_Mode, GL_ONE, GL_ONE_MINUS_SRC_ALPHA },
{ SkXfermode::kDstOver_Mode, GL_ONE_MINUS_DST_ALPHA, GL_ONE },
{ SkXfermode::kSrcIn_Mode, GL_DST_ALPHA, GL_ZERO },
{ SkXfermode::kDstIn_Mode, GL_ZERO, GL_SRC_ALPHA },
{ SkXfermode::kSrcOut_Mode, GL_ONE_MINUS_DST_ALPHA, GL_ZERO },
{ SkXfermode::kDstOut_Mode, GL_ZERO, GL_ONE_MINUS_SRC_ALPHA },
{ SkXfermode::kSrcATop_Mode, GL_DST_ALPHA, GL_ONE_MINUS_SRC_ALPHA },
{ SkXfermode::kDstATop_Mode, GL_ONE_MINUS_DST_ALPHA, GL_SRC_ALPHA },
{ SkXfermode::kXor_Mode, GL_ONE_MINUS_DST_ALPHA, GL_ONE_MINUS_SRC_ALPHA },
{ SkXfermode::kPlus_Mode, GL_ONE, GL_ONE },
{ SkXfermode::kModulate_Mode, GL_ZERO, GL_SRC_COLOR },
{ SkXfermode::kScreen_Mode, GL_ONE, GL_ONE_MINUS_SRC_COLOR }
};
// This array contains the swapped version of each SkXfermode. For instance
// this array's SrcOver blending mode is actually DstOver. You can refer to
// createLayer() for more information on the purpose of this array.
const Blender kBlendsSwap[] = {
{ SkXfermode::kClear_Mode, GL_ONE_MINUS_DST_ALPHA, GL_ZERO },
{ SkXfermode::kSrc_Mode, GL_ZERO, GL_ONE },
{ SkXfermode::kDst_Mode, GL_ONE, GL_ZERO },
{ SkXfermode::kSrcOver_Mode, GL_ONE_MINUS_DST_ALPHA, GL_ONE },
{ SkXfermode::kDstOver_Mode, GL_ONE, GL_ONE_MINUS_SRC_ALPHA },
{ SkXfermode::kSrcIn_Mode, GL_ZERO, GL_SRC_ALPHA },
{ SkXfermode::kDstIn_Mode, GL_DST_ALPHA, GL_ZERO },
{ SkXfermode::kSrcOut_Mode, GL_ZERO, GL_ONE_MINUS_SRC_ALPHA },
{ SkXfermode::kDstOut_Mode, GL_ONE_MINUS_DST_ALPHA, GL_ZERO },
{ SkXfermode::kSrcATop_Mode, GL_ONE_MINUS_DST_ALPHA, GL_SRC_ALPHA },
{ SkXfermode::kDstATop_Mode, GL_DST_ALPHA, GL_ONE_MINUS_SRC_ALPHA },
{ SkXfermode::kXor_Mode, GL_ONE_MINUS_DST_ALPHA, GL_ONE_MINUS_SRC_ALPHA },
{ SkXfermode::kPlus_Mode, GL_ONE, GL_ONE },
{ SkXfermode::kModulate_Mode, GL_DST_COLOR, GL_ZERO },
{ SkXfermode::kScreen_Mode, GL_ONE_MINUS_DST_COLOR, GL_ONE }
};
Blend::Blend()
: mEnabled(false)
, mSrcMode(GL_ZERO)
, mDstMode(GL_ZERO) {
// gl blending off by default
}
void Blend::enable(SkXfermode::Mode mode, bool swapSrcDst) {
// enable
if (!mEnabled) {
glEnable(GL_BLEND);
mEnabled = true;
}
// select blend mode
GLenum sourceMode = swapSrcDst ? kBlendsSwap[mode].src : kBlends[mode].src;
GLenum destMode = swapSrcDst ? kBlendsSwap[mode].dst : kBlends[mode].dst;
if (sourceMode != mSrcMode || destMode != mSrcMode) {
glBlendFunc(sourceMode, destMode);
mSrcMode = sourceMode;
mDstMode = destMode;
}
}
void Blend::disable() {
if (mEnabled) {
glDisable(GL_BLEND);
mEnabled = false;
}
}
void Blend::invalidate() {
syncEnabled();
mSrcMode = mDstMode = GL_ZERO;
}
void Blend::syncEnabled() {
if (mEnabled) {
glEnable(GL_BLEND);
} else {
glDisable(GL_BLEND);
}
}
} /* namespace uirenderer */
} /* namespace android */
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