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      1 /*
      2  * Copyright (C) 2012 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 
     17 #include "renderstate/Stencil.h"
     18 
     19 #include "Caches.h"
     20 #include "Debug.h"
     21 #include "Extensions.h"
     22 #include "Properties.h"
     23 
     24 #include <GLES2/gl2ext.h>
     25 
     26 namespace android {
     27 namespace uirenderer {
     28 
     29 #if DEBUG_STENCIL
     30 #define STENCIL_WRITE_VALUE 0xff
     31 #define STENCIL_MASK_VALUE 0xff
     32 #else
     33 #define STENCIL_WRITE_VALUE 0x1
     34 #define STENCIL_MASK_VALUE 0x1
     35 #endif
     36 
     37 Stencil::Stencil()
     38         : mState(kDisabled) {
     39 }
     40 
     41 uint8_t Stencil::getStencilSize() {
     42     return STENCIL_BUFFER_SIZE;
     43 }
     44 
     45 /**
     46  * This method will return either GL_STENCIL_INDEX4_OES if supported,
     47  * GL_STENCIL_INDEX8 if not.
     48  *
     49  * Layers can't use a single bit stencil because multi-rect ClipArea needs a high enough
     50  * stencil resolution to represent the summation of multiple intersecting rect geometries.
     51  */
     52 GLenum Stencil::getLayerStencilFormat() {
     53 #if !DEBUG_STENCIL
     54     const Extensions& extensions = Caches::getInstance().extensions();
     55     if (extensions.has4BitStencil()) {
     56         return GL_STENCIL_INDEX4_OES;
     57     }
     58 #endif
     59     return GL_STENCIL_INDEX8;
     60 }
     61 
     62 void Stencil::clear() {
     63     glStencilMask(0xff);
     64     glClearStencil(0);
     65     glClear(GL_STENCIL_BUFFER_BIT);
     66 
     67     if (mState == kTest) {
     68         // reset to test state, with immutable stencil
     69         glStencilMask(0);
     70     }
     71 }
     72 
     73 void Stencil::enableTest(int incrementThreshold) {
     74     if (mState != kTest) {
     75         enable();
     76         if (incrementThreshold > 0) {
     77             glStencilFunc(GL_EQUAL, incrementThreshold, 0xff);
     78         } else {
     79             glStencilFunc(GL_EQUAL, STENCIL_WRITE_VALUE, STENCIL_MASK_VALUE);
     80         }
     81         // We only want to test, let's keep everything
     82         glStencilOp(GL_KEEP, GL_KEEP, GL_KEEP);
     83         glColorMask(GL_TRUE, GL_TRUE, GL_TRUE, GL_TRUE);
     84         glStencilMask(0);
     85         mState = kTest;
     86     }
     87 }
     88 
     89 void Stencil::enableWrite(int incrementThreshold) {
     90     if (mState != kWrite) {
     91         enable();
     92         if (incrementThreshold > 0) {
     93             glStencilFunc(GL_ALWAYS, 1, 0xff);
     94             // The test always passes so the first two values are meaningless
     95             glStencilOp(GL_INCR, GL_INCR, GL_INCR);
     96         } else {
     97             glStencilFunc(GL_ALWAYS, STENCIL_WRITE_VALUE, STENCIL_MASK_VALUE);
     98             // The test always passes so the first two values are meaningless
     99             glStencilOp(GL_KEEP, GL_KEEP, GL_REPLACE);
    100         }
    101         glColorMask(GL_FALSE, GL_FALSE, GL_FALSE, GL_FALSE);
    102         glStencilMask(0xff);
    103         mState = kWrite;
    104     }
    105 }
    106 
    107 void Stencil::enableDebugTest(GLint value, bool greater) {
    108     enable();
    109     glStencilFunc(greater ? GL_LESS : GL_EQUAL, value, 0xffffffff);
    110     // We only want to test, let's keep everything
    111     glStencilOp(GL_KEEP, GL_KEEP, GL_KEEP);
    112     mState = kTest;
    113     glStencilMask(0);
    114 }
    115 
    116 void Stencil::enableDebugWrite() {
    117     enable();
    118     glStencilFunc(GL_ALWAYS, 0x1, 0xffffffff);
    119     // The test always passes so the first two values are meaningless
    120     glStencilOp(GL_KEEP, GL_KEEP, GL_INCR);
    121     glColorMask(GL_TRUE, GL_TRUE, GL_TRUE, GL_TRUE);
    122     mState = kWrite;
    123     glStencilMask(0xff);
    124 }
    125 
    126 void Stencil::enable() {
    127     if (mState == kDisabled) {
    128         glEnable(GL_STENCIL_TEST);
    129     }
    130 }
    131 
    132 void Stencil::disable() {
    133     if (mState != kDisabled) {
    134         glDisable(GL_STENCIL_TEST);
    135         mState = kDisabled;
    136     }
    137 }
    138 
    139 void Stencil::dump() {
    140     ALOGD("Stencil: state %d", mState);
    141 }
    142 
    143 }; // namespace uirenderer
    144 }; // namespace android
    145