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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 #ifndef ANDROID_HWUI_STENCIL_H
     18 #define ANDROID_HWUI_STENCIL_H
     19 
     20 #ifndef LOG_TAG
     21     #define LOG_TAG "OpenGLRenderer"
     22 #endif
     23 
     24 #include <GLES2/gl2.h>
     25 
     26 #include <cutils/compiler.h>
     27 
     28 namespace android {
     29 namespace uirenderer {
     30 
     31 ///////////////////////////////////////////////////////////////////////////////
     32 // Stencil buffer management
     33 ///////////////////////////////////////////////////////////////////////////////
     34 
     35 class ANDROID_API Stencil {
     36 public:
     37     Stencil();
     38 
     39     /**
     40      * Returns the desired size for the stencil buffer. If the returned value
     41      * is 0, then no stencil buffer is required.
     42      */
     43     ANDROID_API static uint8_t getStencilSize();
     44 
     45     static GLenum getLayerStencilFormat();
     46 
     47     /**
     48      * Clears the stencil buffer.
     49      */
     50     void clear();
     51 
     52     /**
     53      * Enables stencil test. When the stencil test is enabled the stencil buffer is not written
     54      * into. An increment threshold of zero causes the stencil to use a constant reference value
     55      * and GL_EQUAL for the test. A non-zero increment threshold causes the stencil to use that
     56      * value as the reference value and GL_EQUAL for the test.
     57      */
     58     void enableTest(int incrementThreshold);
     59 
     60     /**
     61      * Enables stencil write. When stencil write is enabled, the stencil
     62      * test always succeeds and the value 0x1 is written in the stencil
     63      * buffer for each fragment. An increment threshold of zero causes the stencil to use a constant
     64      * reference value and GL_EQUAL for the test. A non-zero increment threshold causes the stencil
     65      * to use that value as the reference value and GL_EQUAL for the test.
     66      */
     67     void enableWrite(int incrementThreshold);
     68 
     69     /**
     70      * The test passes only when equal to the specified value.
     71      */
     72     void enableDebugTest(GLint value, bool greater = false);
     73 
     74     /**
     75      * Used for debugging. The stencil test always passes and increments.
     76      */
     77     void enableDebugWrite();
     78 
     79     /**
     80      * Disables stencil test and write.
     81      */
     82     void disable();
     83 
     84     /**
     85      * Indicates whether either test or write is enabled.
     86      */
     87     bool isEnabled() {
     88         return mState != kDisabled;
     89     }
     90 
     91     /**
     92      * Indicates whether testing only is enabled.
     93      */
     94     bool isTestEnabled() {
     95         return mState == kTest;
     96     }
     97 
     98     bool isWriteEnabled() {
     99         return mState == kWrite;
    100     }
    101 
    102     void dump();
    103 
    104 private:
    105     void enable();
    106 
    107     enum StencilState {
    108         kDisabled,
    109         kTest,
    110         kWrite
    111     };
    112 
    113     StencilState mState;
    114 
    115 }; // class Stencil
    116 
    117 }; // namespace uirenderer
    118 }; // namespace android
    119 
    120 #endif // ANDROID_HWUI_STENCIL_H
    121