query.hpp

/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#pragma once

#include <gls/headercheck.hpp>
#include <gls/errorcheck.hpp>
#include <gls/objects/object.hpp>
#include <cassert>

namespace gls {

namespace priv {
    void gen_queries( GLsizei size, GLuint* name ) { glGenQueries( size, name ); }
    void delete_queries( GLsizei size, const GLuint* name ) { glDeleteQueries( size, name ); }
}

template<GLenum Target>
class query {
public:
    GLuint name() const {
        return m_object.name();
    }

    template<typename T>
    void run( T callable ) {
        if( m_waiting ) {
            callable();
            return;
        }

        m_waiting = true;

        check_gl_error( glBeginQuery( Target, m_object.name() ) );
        callable();
        check_gl_error( glEndQuery( Target ) );
    }

    void begin() {
        if( m_waiting ) {
            return;
        }

        m_waiting = true;

        check_gl_error( glBeginQuery( Target, m_object.name() ) );
    }

    void end() {
        check_gl_error( glEndQuery( Target ) );
    }

    bool poll_result( GLint& result ) {
        if( m_waiting && !ready() ) {
            return false;
        }

        check_gl_error( glGetQueryObjectiv( name(), GL_QUERY_RESULT, &result ) );

        return true;
    }

    bool poll_result( GLuint& result ) {
        if( m_waiting && !ready() ) {
            return false;
        }

        check_gl_error( glGetQueryObjectuiv( name(), GL_QUERY_RESULT, &result ) );

        return true;
    }

private:
    bool ready() {
        auto result_ready = GLuint();

        check_gl_error( glGetQueryObjectuiv( name(), GL_QUERY_RESULT_AVAILABLE, &result_ready ) );

        m_waiting = ( result_ready == GL_FALSE );

        return result_ready == GL_TRUE;
    }

    object<priv::gen_queries, priv::delete_queries> m_object;
    bool m_waiting = false;
};

}