mutter/doc/clutter-frame-scheduling.md

# Clutter Frame scheduling

`ClutterFrameClock` state diagram.

```mermaid
stateDiagram
    Init --> Scheduled/ScheduledNow : schedule update() -> now
    Idle --> Scheduled/ScheduledNow : schedule update() -> given presentation time
    Scheduled/ScheduledNow --> Dispatching : target time hit
    Dispatching --> PendingPresented : queued page flip
    Dispatching --> Idle : no queued page flip
    PendingPresented --> Scheduled/ScheduledNow : page flipped, if recent schedule update
    PendingPresented --> Idle : page flipped
```
docs: Prefix code documentation files with the subsystem they belong to. This makes it easier to see which files belong where. Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/3485> 2024-01-03 16:30:16 -05:00			`# Clutter Frame scheduling`
docs: Move the gitlab wiki and other docs to the docs/ directory Let's try to consolidate our documentation in doc/ in the repo. This includes some documentation from README.md, the HACKING.md coding style and the gitlab wiki. The README.md file now links to all top-level topics (i.e. not reachable via other topics). This also includes a few small changes to make things more consistent. Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/3465> 2023-12-18 11:30:53 -05:00
			`ClutterFrameClock` state diagram.

			```mermaid
			`stateDiagram`
clutter/frame-clock: Add a state for when scheduled "now" The new CLUTTER_FRAME_CLOCK_STATE_SCHEDULED_NOW state is almost identical to CLUTTER_FRAME_CLOCK_STATE_SCHEDULED, with one important difference being that it avoids updates from being repeatedly rescheduled "now" when multiple calls to clutter_frame_clock_schedule_update_now() are done before the source is actually dispatched. Such repeated calls to schedule an update "now" may actually postpone the dispatch if the CPU is very busy and the source dispatch is delayed, defeating the purpose of scheduling a frame "now". It also allows rescheduling "now" when the frame clock is uninhibited after being inhibited while an update was scheduled "now". This may be important in cases where the frame clock is inhibited for very short periods in which it would otherwise lose the state of being scheduled "now". Scenarios such as this would become more common with the introduction of variable refresh rate since it makes scheduling "now" a commonplace occurrence. Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/3561> 2024-02-03 17:54:45 -05:00			`Init --> Scheduled/ScheduledNow : schedule update() -> now`
			`Idle --> Scheduled/ScheduledNow : schedule update() -> given presentation time`
			`Scheduled/ScheduledNow --> Dispatching : target time hit`
docs: Move the gitlab wiki and other docs to the docs/ directory Let's try to consolidate our documentation in doc/ in the repo. This includes some documentation from README.md, the HACKING.md coding style and the gitlab wiki. The README.md file now links to all top-level topics (i.e. not reachable via other topics). This also includes a few small changes to make things more consistent. Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/3465> 2023-12-18 11:30:53 -05:00			`Dispatching --> PendingPresented : queued page flip`
			`Dispatching --> Idle : no queued page flip`
clutter/frame-clock: Add a state for when scheduled "now" The new CLUTTER_FRAME_CLOCK_STATE_SCHEDULED_NOW state is almost identical to CLUTTER_FRAME_CLOCK_STATE_SCHEDULED, with one important difference being that it avoids updates from being repeatedly rescheduled "now" when multiple calls to clutter_frame_clock_schedule_update_now() are done before the source is actually dispatched. Such repeated calls to schedule an update "now" may actually postpone the dispatch if the CPU is very busy and the source dispatch is delayed, defeating the purpose of scheduling a frame "now". It also allows rescheduling "now" when the frame clock is uninhibited after being inhibited while an update was scheduled "now". This may be important in cases where the frame clock is inhibited for very short periods in which it would otherwise lose the state of being scheduled "now". Scenarios such as this would become more common with the introduction of variable refresh rate since it makes scheduling "now" a commonplace occurrence. Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/3561> 2024-02-03 17:54:45 -05:00			`PendingPresented --> Scheduled/ScheduledNow : page flipped, if recent schedule update`
docs: Move the gitlab wiki and other docs to the docs/ directory Let's try to consolidate our documentation in doc/ in the repo. This includes some documentation from README.md, the HACKING.md coding style and the gitlab wiki. The README.md file now links to all top-level topics (i.e. not reachable via other topics). This also includes a few small changes to make things more consistent. Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/3465> 2023-12-18 11:30:53 -05:00			`PendingPresented --> Idle : page flipped`
			```