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      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 
     24 namespace android {
     25 namespace 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  */
     40 class Query {
     41 public:
     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 
    141 private:
    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