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      */
isEnabled()87     bool isEnabled() {
88         return mState != kDisabled;
89     }
90 
91     /**
92      * Indicates whether testing only is enabled.
93      */
isTestEnabled()94     bool isTestEnabled() {
95         return mState == kTest;
96     }
97 
isWriteEnabled()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