chromium/ui/gl/gpu_timing.h

// Copyright 2015 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef UI_GL_GPU_TIMING_H_
#define UI_GL_GPU_TIMING_H_

#include <stdint.h>

#include <memory>
#include <queue>

#include "base/functional/callback.h"
#include "base/memory/raw_ptr.h"
#include "ui/gl/gl_export.h"

// The gpu_timing classes handles the abstraction of GL GPU Timing extensions
// into a common set of functions. Currently the different timer extensions that
// are supported are EXT_timer_query, ARB_timer_query and
// EXT_disjoint_timer_query.
//
// Explanation of Classes:
//   GPUTiming - GPU Timing is a private class which is only owned by the
//     underlying GLContextReal class. This class handles any GL Context level
//     states which may need to be redistributed to users of GPUTiming. For
//     example, there exists only a single disjoint flag for each real GL
//     Context. Once the disjoint flag is checked, internally it is reset to
//     false. In order to support multiple virtual contexts each checking the
//     disjoint flag seperately, GPUTiming is in charge of checking the
//     disjoint flag and broadcasting out the disjoint state to all the
//     various users of GPUTiming (GPUTimingClient below).
//   GPUTimingClient - The GLContextReal holds the GPUTiming class and is the
//     factory that creates GPUTimingClient objects. If a user would like to
//     obtain various GPU times they would access CreateGPUTimingClient() from
//     their GLContext and use the returned object for their timing calls.
//     Each virtual context as well as any other classes which need GPU times
//     will hold one of these. When they want to time a set of GL commands they
//     will create GPUTimer objects.
//   GPUTimer - Once a user decides to time something, the user creates a new
//     GPUTimer object from a GPUTimingClient and issue Start() and Stop() calls
//     around various GL calls. Once IsAvailable() returns true, the GPU times
//     will be available through the various time stamp related functions.
//     The constructor and destructor of this object handles the actual
//     creation and deletion of the GL Queries within GL.

namespace gl {

class GLContextReal;
class GPUTimingClient;
class GPUTimingImpl;
class QueryResult;

class GPUTiming { … };

// Class to compute the amount of time it takes to fully
// complete a set of GL commands
class GL_EXPORT GPUTimer { … };

// GPUTimingClient contains all the gl timing logic that is not specific
// to a single GPUTimer.
class GL_EXPORT GPUTimingClient
    : public base::RefCounted<GPUTimingClient> { … };

}  // namespace gl

#endif  // UI_GL_GPU_TIMING_H_