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Currently, all timelines install a timeout inside the TimeoutPool
they share. Every time the main loop spins, all the timeouts are
updated. This, in turn, will usually lead to redraws being queued
on the stages.
This behaviour leads to the potential starvation of timelines and
to excessive redraws.
One lesson learned from the games developers is that the scenegraph
should be prepared in its entirety before the GL paint sequence is
initiated. This means making sure that every ::new-frame signal
handler is called before clutter_redraw() is invoked.
In order to do so a TimeoutPool is not enough: we need a master
clock. The clock will be responsible for advancing all the active
timelines created inside a scene, but only when the stage is
being redrawn.
The sequence is:
+ queue_redraw() is invoked on an actor and bubbles up
to the stage
+ if no redraw() has already been scheduled, install an
idle handler with a known priority
+ inside the idle handler:
- advance the master clock, which will in turn advance
every playing timeline by the amount of milliseconds
elapsed since the last redraw; this will make every
playing timeline emit the ::new-frame signal
- queue a relayout
- call the redraw() method of the backend
This way we trade multiple timeouts with a single frame source
that only runs if a timeline is playing and queues redraws on
the various stages.
49 lines
1.9 KiB
C
49 lines
1.9 KiB
C
/*
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* Clutter.
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*
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* An OpenGL based 'interactive canvas' library.
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*
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* Authored By: Emmanuele Bassi <ebassi@linux.intel.com>
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*
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* Copyright (C) 2009 Intel Corporation.
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*
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2 of the License, or (at your option) any later version.
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*
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* This library is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with this library. If not, see <http://www.gnu.org/licenses/>.
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*/
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#ifndef __CLUTTER_MASTER_CLOCK_H__
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#define __CLUTTER_MASTER_CLOCK_H__
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#include <clutter/clutter-timeline.h>
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G_BEGIN_DECLS
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#define CLUTTER_TYPE_MASTER_CLOCK (clutter_master_clock_get_type ())
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#define CLUTTER_MASTER_CLOCK(obj) (G_TYPE_CHECK_INSTANCE_CAST ((obj), CLUTTER_TYPE_MASTER_CLOCK, ClutterMasterClock))
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#define CLUTTER_IS_MASTER_CLOCK(obj) (G_TYPE_CHECK_INSTANCE_TYPE ((obj), CLUTTER_TYPE_MASTER_CLOCK))
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typedef struct _ClutterMasterClock ClutterMasterClock;
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GType clutter_master_clock_get_type (void) G_GNUC_CONST;
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ClutterMasterClock *_clutter_master_clock_get_default (void);
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void _clutter_master_clock_add_timeline (ClutterMasterClock *master_clock,
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ClutterTimeline *timeline);
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void _clutter_master_clock_remove_timeline (ClutterMasterClock *master_clock,
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ClutterTimeline *timeline);
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void _clutter_master_clock_advance (ClutterMasterClock *master_clock);
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G_END_DECLS
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#endif /* __CLUTTER_MASTER_CLOCK_H__ */
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