1/*
2 * Copyright (C) 2013 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_QUERY_H
18#define ANDROID_HWUI_QUERY_H
19
20#include <GLES3/gl3.h>
21
22#include "Extensions.h"
23
24namespace android {
25namespace uirenderer {
26
27/**
28 * A Query instance can be used to perform occlusion queries. If the device
29 * does not support occlusion queries, the result of a query will always be
30 * 0 and the result will always be marked available.
31 *
32 * To run an occlusion query successfully, you must start end end the query:
33 *
34 * Query query;
35 * query.begin();
36 * // execute OpenGL calls
37 * query.end();
38 * GLuint result = query.getResult();
39 */
40class Query {
41public:
42    /**
43     * Possible query targets.
44     */
45    enum Target {
46        /**
47         * Indicates if any sample passed the depth & stencil tests.
48         */
49        kTargetSamples = GL_ANY_SAMPLES_PASSED,
50        /**
51         * Indicates if any sample passed the depth & stencil tests.
52         * The implementation may choose to use a less precise version
53         * of the test, potentially resulting in false positives.
54         */
55        kTargetConservativeSamples = GL_ANY_SAMPLES_PASSED_CONSERVATIVE,
56    };
57
58    /**
59     * Creates a new query with the specified target. The default
60     * target is kTargetSamples (of GL_ANY_SAMPLES_PASSED in OpenGL.)
61     */
62    Query(Target target = kTargetSamples): mActive(false), mTarget(target),
63            mCanQuery(Extensions::getInstance().hasOcclusionQueries()),
64            mQuery(0) {
65    }
66
67    ~Query() {
68        if (mQuery) {
69            glDeleteQueries(1, &mQuery);
70        }
71    }
72
73    /**
74     * Begins the query. If the query has already begun or if the device
75     * does not support occlusion queries, calling this method as no effect.
76     * After calling this method successfully, the query is marked active.
77     */
78    void begin() {
79        if (!mActive && mCanQuery) {
80            if (!mQuery) {
81                glGenQueries(1, &mQuery);
82            }
83
84            glBeginQuery(mTarget, mQuery);
85            mActive = true;
86        }
87    }
88
89    /**
90     * Ends the query. If the query has already begun or if the device
91     * does not support occlusion queries, calling this method as no effect.
92     * After calling this method successfully, the query is marked inactive.
93     */
94    void end() {
95        if (mQuery && mActive) {
96            glEndQuery(mTarget);
97            mActive = false;
98        }
99    }
100
101    /**
102     * Returns true if the query is active, false otherwise.
103     */
104    bool isActive() {
105        return mActive;
106    }
107
108    /**
109     * Returns true if the result of the query is available,
110     * false otherwise. Calling getResult() before the result
111     * is available may result in the calling thread being blocked.
112     * If the device does not support queries, this method always
113     * returns true.
114     */
115    bool isResultAvailable() {
116        if (!mQuery) return true;
117
118        GLuint result;
119        glGetQueryObjectuiv(mQuery, GL_QUERY_RESULT_AVAILABLE, &result);
120        return result == GL_TRUE;
121    }
122
123    /**
124     * Returns the result of the query. If the device does not
125     * support queries this method will return 0.
126     *
127     * Calling this method implicitely calls end() if the query
128     * is currently active.
129     */
130    GLuint getResult() {
131        if (!mQuery) return 0;
132
133        end();
134
135        GLuint result;
136        glGetQueryObjectuiv(mQuery, GL_QUERY_RESULT, &result);
137        return result;
138    }
139
140
141private:
142    bool mActive;
143    GLenum mTarget;
144    bool mCanQuery;
145    GLuint mQuery;
146
147}; // class Query
148
149}; // namespace uirenderer
150}; // namespace android
151
152#endif // ANDROID_HWUI_QUERY_H
153