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