mutter/clutter/clutter-timeout-interval.c
Neil Roberts a93a93d007 Count timeline frames using the FPS instead of an integer interval
Bug 1495 - Timelines run 4% short

Previously the timelines were timed by calculating the interval
between each frame stored as an integer number of milliseconds so some
precision is lost. For example, requesting 60 frames per second gets
converted to 16 ms per frame which is actually 62.5 frames per
second. This makes the timeline shorter by 4%.

This patch merges the common code for timing from the timeout pools
and frame sources into an internal clutter-timeout-interval file. This
stores the interval directly as the FPS and counts the number of
frames that have been reached instead of the elapsed time.
2009-03-16 15:40:18 +00:00

127 lines
3.8 KiB
C

/*
* Clutter.
*
* An OpenGL based 'interactive canvas' library.
*
* Authored By Neil Roberts <neil@linux.intel.com>
*
* Copyright (C) 2009 Intel Corporation.
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library. If not, see <http://www.gnu.org/licenses/>.
*/
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif
/* This file contains the common code to check whether an interval has
expired used in clutter-frame-source and clutter-timeout-pool. */
#include "clutter-timeout-interval.h"
void
_clutter_timeout_interval_init (ClutterTimeoutInterval *interval,
guint fps)
{
g_get_current_time (&interval->start_time);
interval->fps = fps;
interval->frame_count = 0;
}
static guint
_clutter_timeout_interval_get_ticks (const GTimeVal *current_time,
ClutterTimeoutInterval *interval)
{
return ((current_time->tv_sec - interval->start_time.tv_sec) * 1000
+ (current_time->tv_usec - interval->start_time.tv_usec) / 1000);
}
gboolean
_clutter_timeout_interval_prepare (const GTimeVal *current_time,
ClutterTimeoutInterval *interval,
gint *delay)
{
guint elapsed_time
= _clutter_timeout_interval_get_ticks (current_time, interval);
guint new_frame_num = elapsed_time * interval->fps / 1000;
/* If time has gone backwards or the time since the last frame is
greater than the two frames worth then reset the time and do a
frame now */
if (new_frame_num < interval->frame_count ||
new_frame_num - interval->frame_count > 2)
{
/* Get the frame time rounded up to the nearest ms */
guint frame_time = (1000 + interval->fps - 1) / interval->fps;
/* Reset the start time */
interval->start_time = *current_time;
/* Move the start time as if one whole frame has elapsed */
g_time_val_add (&interval->start_time, -(gint) frame_time * 1000);
interval->frame_count = 0;
if (delay)
*delay = 0;
return TRUE;
}
else if (new_frame_num > interval->frame_count)
{
if (delay)
*delay = 0;
return TRUE;
}
else
{
if (delay)
*delay = ((interval->frame_count + 1) * 1000 / interval->fps
- elapsed_time);
return FALSE;
}
}
gboolean
_clutter_timeout_interval_dispatch (ClutterTimeoutInterval *interval,
GSourceFunc callback,
gpointer user_data)
{
if ((* callback) (user_data))
{
interval->frame_count++;
return TRUE;
}
else
return FALSE;
}
gint
_clutter_timeout_interval_compare_expiration (const ClutterTimeoutInterval *a,
const ClutterTimeoutInterval *b)
{
guint a_delay = 1000 / a->fps;
guint b_delay = 1000 / b->fps;
glong b_difference;
gint comparison;
b_difference = ((a->start_time.tv_sec - b->start_time.tv_sec) * 1000
+ (a->start_time.tv_usec - b->start_time.tv_usec) / 1000);
comparison = ((gint) ((a->frame_count + 1) * a_delay)
- (gint) ((b->frame_count + 1) * b_delay + b_difference));
return (comparison < 0 ? -1
: comparison > 0 ? 1
: 0);
}