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/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
//! A timer thread that gives the painting thread a little time to catch up when the user scrolls.
use compositor_thread::{CompositorProxy, Msg};
use std::sync::mpsc::{Receiver, Sender, channel};
use std::thread::{self, Builder};
use time;
use util::time::duration_from_nanoseconds;
/// The amount of time in nanoseconds that we give to the painting thread to paint new tiles upon
/// processing a scroll event that caused new tiles to be revealed. When this expires, we give up
/// and composite anyway (showing a "checkerboard") to avoid dropping the frame.
static TIMEOUT: u64 = 12_000_000;
pub struct ScrollingTimerProxy {
sender: Sender<ToScrollingTimerMsg>,
}
pub struct ScrollingTimer {
compositor_proxy: Box<CompositorProxy>,
receiver: Receiver<ToScrollingTimerMsg>,
}
enum ToScrollingTimerMsg {
ExitMsg,
ScrollEventProcessedMsg(u64),
}
impl ScrollingTimerProxy {
pub fn new(compositor_proxy: Box<CompositorProxy + Send>) -> ScrollingTimerProxy {
let (to_scrolling_timer_sender, to_scrolling_timer_receiver) = channel();
Builder::new().spawn(move || {
let mut scrolling_timer = ScrollingTimer {
compositor_proxy: compositor_proxy,
receiver: to_scrolling_timer_receiver,
};
scrolling_timer.run();
}).unwrap();
ScrollingTimerProxy {
sender: to_scrolling_timer_sender,
}
}
pub fn scroll_event_processed(&mut self, timestamp: u64) {
self.sender.send(ToScrollingTimerMsg::ScrollEventProcessedMsg(timestamp)).unwrap()
}
pub fn shutdown(&mut self) {
self.sender.send(ToScrollingTimerMsg::ExitMsg).unwrap()
}
}
impl ScrollingTimer {
pub fn run(&mut self) {
while let Ok(ToScrollingTimerMsg::ScrollEventProcessedMsg(timestamp)) = self.receiver.recv() {
let target = timestamp + TIMEOUT;
let delta_ns = target - time::precise_time_ns();
thread::sleep(duration_from_nanoseconds(delta_ns));
self.compositor_proxy.send(Msg::ScrollTimeout(timestamp));
}
}
}
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