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//! VBlank throttling.
//!
//! Some buggy drivers deliver VBlanks way earlier than necessary. This helper throttles the VBlank
//! in such cases to avoid tearing and to get more consistent timings.
use std::time::Duration;
use calloop::timer::{TimeoutAction, Timer};
use calloop::{LoopHandle, RegistrationToken};
use crate::niri::State;
#[derive(Debug)]
pub struct VBlankThrottle {
event_loop: LoopHandle<'static, State>,
last_vblank_timestamp: Option<Duration>,
throttle_timer_token: Option<RegistrationToken>,
printed_warning: bool,
output_name: String,
}
impl VBlankThrottle {
pub fn new(event_loop: LoopHandle<'static, State>, output_name: String) -> Self {
Self {
event_loop,
last_vblank_timestamp: None,
throttle_timer_token: None,
printed_warning: false,
output_name,
}
}
pub fn throttle(
&mut self,
refresh_interval: Option<Duration>,
timestamp: Duration,
mut call_vblank: impl FnMut(&mut State) + 'static,
) -> bool {
if let Some(token) = self.throttle_timer_token.take() {
self.event_loop.remove(token);
}
if let Some((last, refresh)) = Option::zip(self.last_vblank_timestamp, refresh_interval) {
let passed = timestamp.saturating_sub(last);
if passed < refresh / 2 {
if !self.printed_warning {
self.printed_warning = true;
warn!(
"output {} running faster than expected, throttling vblanks: \
expected refresh {refresh:?}, got vblank after {passed:?}",
self.output_name
);
}
let remaining = refresh - passed;
let token = self
.event_loop
.insert_source(Timer::from_duration(remaining), move |_, _, state| {
call_vblank(state);
TimeoutAction::Drop
})
.unwrap();
self.throttle_timer_token = Some(token);
return true;
}
}
self.last_vblank_timestamp = Some(timestamp);
false
}
}
|
