Implement timers for the X11 platform (#1096)

psychon · web-flow · commit cffde32a8126 · 2020-07-20T21:42:06.000-05:00
Fixes-half-of: #934 Signed-off-by: Uli Schlachter <psychon@znc.in>
diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -36,6 +36,7 @@ You can find its changes [documented below](#060---2020-06-01).
 - X11: Support idle callbacks. ([#1072] by [@jneem])
 - GTK: Don't interrupt `KeyEvent.repeat` when releasing another key. ([#1081] by [@raphlinus])
 - X11: Set some more common window properties. ([#1097] by [@psychon])
+- X11: Support timers. ([#1096] by [@psychon])
 
 ### Visual
 
@@ -362,6 +363,7 @@ Last release without a changelog :(
 [#1075]: https://github.com/linebender/druid/pull/1075
 [#1076]: https://github.com/linebender/druid/pull/1076
 [#1081]: https://github.com/linebender/druid/pull/1081
+[#1096]: https://github.com/linebender/druid/pull/1096
 [#1097]: https://github.com/linebender/druid/pull/1097
 
 [Unreleased]: https://github.com/linebender/druid/compare/v0.6.0...master
diff --git a/druid-shell/src/platform/x11/application.rs b/druid-shell/src/platform/x11/application.rs
@@ -381,7 +381,18 @@ impl Application {
         let timeout = Duration::from_millis((1000.0 / refresh_rate) as u64);
         let mut last_idle_time = Instant::now();
         loop {
+            // Figure out when the next wakeup needs to happen
+            let next_timeout = if let Ok(state) = self.state.try_borrow() {
+                state.windows
+                    .values()
+                    .filter_map(|w| w.next_timeout())
+                    .min()
+            } else {
+                log::error!("Getting next timeout, application state already borrowed");
+                None
+            };
             let next_idle_time = last_idle_time + timeout;
+
             self.connection.flush()?;
 
             // Before we poll on the connection's file descriptor, check whether there are any
@@ -390,7 +401,7 @@ impl Application {
             let mut event = self.connection.poll_for_event()?;
 
             if event.is_none() {
-                poll_with_timeout(&self.connection, self.idle_read, next_idle_time)
+                poll_with_timeout(&self.connection, self.idle_read, next_timeout, next_idle_time)
                     .context("Error while waiting for X11 connection")?;
             }
 
@@ -409,6 +420,17 @@ impl Application {
             }
 
             let now = Instant::now();
+            if let Some(timeout) = next_timeout {
+                if timeout <= now {
+                    if let Ok(state) = self.state.try_borrow() {
+                        for w in state.windows.values() {
+                            w.run_timers(now);
+                        }
+                    } else {
+                        log::error!("In timer loop, application state already borrowed");
+                    }
+                }
+            }
             if now >= next_idle_time {
                 last_idle_time = now;
                 drain_idle_pipe(self.idle_read)?;
@@ -510,11 +532,13 @@ fn drain_idle_pipe(idle_read: RawFd) -> Result<(), Error> {
 /// writing into our idle pipe and the `timeout` has passed.
 // This was taken, with minor modifications, from the xclock_utc example in the x11rb crate.
 // https://github.com/psychon/x11rb/blob/a6bd1453fd8e931394b9b1f2185fad48b7cca5fe/examples/xclock_utc.rs
-fn poll_with_timeout(conn: &Rc<XCBConnection>, idle: RawFd, timeout: Instant) -> Result<(), Error> {
+fn poll_with_timeout(conn: &Rc<XCBConnection>, idle: RawFd, timer_timeout: Option<Instant>, idle_timeout: Instant) -> Result<(), Error> {
     use nix::poll::{poll, PollFd, PollFlags};
     use std::os::raw::c_int;
     use std::os::unix::io::AsRawFd;
 
+    let mut now = Instant::now();
+    let earliest_timeout = idle_timeout.min(timer_timeout.unwrap_or(idle_timeout));
     let fd = conn.as_raw_fd();
     let mut both_poll_fds = [
         PollFd::new(fd, PollFlags::POLLIN),
@@ -525,36 +549,60 @@ fn poll_with_timeout(conn: &Rc<XCBConnection>, idle: RawFd, timeout: Instant) ->
 
     // We start with no timeout in the poll call. If we get something from the idle handler, we'll
     // start setting one.
-    let mut poll_timeout = -1;
+    let mut honor_idle_timeout = false;
     loop {
         fn readable(p: PollFd) -> bool {
             p.revents()
                 .unwrap_or_else(PollFlags::empty)
                 .contains(PollFlags::POLLIN)
         };
 
+        // Compute the deadline for when poll() has to wakeup
+        let deadline = if honor_idle_timeout {
+            Some(earliest_timeout)
+        } else {
+            timer_timeout
+        };
+        // ...and convert the deadline into an argument for poll()
+        let poll_timeout = if let Some(deadline) = deadline {
+            if deadline <= now {
+                break;
+            } else {
+                let millis = c_int::try_from(deadline.duration_since(now).as_millis())
+                    .unwrap_or(c_int::max_value() - 1);
+                // The above .as_millis() rounds down. This means we would wake up before the
+                // deadline is reached. Add one to 'simulate' rounding up instead.
+                millis + 1
+            }
+        } else {
+            // No timeout
+            -1
+        };
+
         match poll(poll_fds, poll_timeout) {
             Ok(_) => {
                 if readable(poll_fds[0]) {
                     // There is an X11 event ready to be handled.
                     break;
                 }
+                now = Instant::now();
+                if timer_timeout.is_some() && now >= timer_timeout.unwrap() {
+                    break;
+                }
                 if poll_fds.len() == 1 || readable(poll_fds[1]) {
                     // Now that we got signalled, stop polling from the idle pipe and use a timeout
                     // instead.
                     poll_fds = &mut just_connection;
-
-                    let now = Instant::now();
-                    if now >= timeout {
+                    honor_idle_timeout = true;
+                    if now >= idle_timeout {
                         break;
-                    } else {
-                        poll_timeout = c_int::try_from(timeout.duration_since(now).as_millis())
-                            .unwrap_or(c_int::max_value())
                     }
                 }
             }
 
-            Err(nix::Error::Sys(nix::errno::Errno::EINTR)) => {}
+            Err(nix::Error::Sys(nix::errno::Errno::EINTR)) => {
+                now = Instant::now();
+            }
             Err(e) => return Err(e.into()),
         }
     }
diff --git a/druid-shell/src/platform/x11/util.rs b/druid-shell/src/platform/x11/util.rs
@@ -14,13 +14,17 @@
 
 //! Miscellaneous utility functions for working with X11.
 
+use std::cmp::Ordering;
 use std::rc::Rc;
+use std::time::Instant;
 
 use anyhow::{anyhow, Error};
 use x11rb::protocol::randr::{ConnectionExt, ModeFlag};
 use x11rb::protocol::xproto::{Screen, Visualtype, Window};
 use x11rb::xcb_ffi::XCBConnection;
 
+use crate::window::TimerToken;
+
 // See: https://github.com/rtbo/rust-xcb/blob/master/examples/randr_screen_modes.rs
 pub fn refresh_rate(conn: &Rc<XCBConnection>, window_id: Window) -> Option<f64> {
     let try_refresh_rate = || -> Result<f64, Error> {
@@ -87,3 +91,40 @@ macro_rules! log_x11 {
         }
     };
 }
+
+/// A timer is a deadline (`std::Time::Instant`) and a `TimerToken`.
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub(crate) struct Timer {
+    deadline: Instant,
+    token: TimerToken,
+}
+
+impl Timer {
+    pub(crate) fn new(deadline: Instant) -> Self {
+        let token = TimerToken::next();
+        Self { deadline, token }
+    }
+
+    pub(crate) fn deadline(&self) -> Instant {
+        self.deadline
+    }
+
+    pub(crate) fn token(&self) -> TimerToken {
+        self.token
+    }
+}
+
+impl Ord for Timer {
+    /// Ordering is so that earliest deadline sorts first
+    // "Earliest deadline first" that a std::collections::BinaryHeap will have the earliest timer
+    // at its head, which is just what is needed for timer management.
+    fn cmp(&self, other: &Self) -> Ordering {
+        self.deadline.cmp(&other.deadline).reverse()
+    }
+}
+
+impl PartialOrd for Timer {
+    fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
+        Some(self.cmp(other))
+    }
+}
diff --git a/druid-shell/src/platform/x11/window.rs b/druid-shell/src/platform/x11/window.rs
@@ -17,9 +17,11 @@
 use std::any::Any;
 use std::cell::RefCell;
 use std::convert::{TryFrom, TryInto};
+use std::collections::BinaryHeap;
 use std::os::unix::io::RawFd;
 use std::rc::{Rc, Weak};
 use std::sync::{Arc, Mutex};
+use std::time::Instant;
 
 use anyhow::{anyhow, Context, Error};
 use cairo::{XCBConnection as CairoXCBConnection, XCBDrawable, XCBSurface, XCBVisualType};
@@ -47,7 +49,7 @@ use crate::window::{IdleToken, Text, TimerToken, WinHandler};
 use super::application::Application;
 use super::keycodes;
 use super::menu::Menu;
-use super::util;
+use super::util::{self, Timer};
 
 /// A version of XCB's `xcb_visualtype_t` struct. This was copied from the [example] in x11rb; it
 /// is used to interoperate with cairo.
@@ -296,6 +298,7 @@ impl WindowBuilder {
             cairo_surface,
             atoms,
             state,
+            timer_queue: Mutex::new(BinaryHeap::new()),
             idle_queue: Arc::new(Mutex::new(Vec::new())),
             idle_pipe: self.app.idle_pipe(),
             present_data: RefCell::new(present_data),
@@ -350,6 +353,8 @@ pub(crate) struct Window {
     cairo_surface: RefCell<XCBSurface>,
     atoms: WindowAtoms,
     state: RefCell<WindowState>,
+    /// Timers, sorted by "earliest deadline first"
+    timer_queue: Mutex<BinaryHeap<Timer>>,
     idle_queue: Arc<Mutex<Vec<IdleKind>>>,
     // Writing to this wakes up the event loop, so that it can run idle handlers.
     idle_pipe: RawFd,
@@ -1004,6 +1009,27 @@ impl Window {
             }
         }
     }
+
+    pub(crate) fn next_timeout(&self) -> Option<Instant> {
+        if let Some(timer) = self.timer_queue.lock().unwrap().peek() {
+            Some(timer.deadline())
+        } else {
+            None
+        }
+    }
+
+    pub(crate) fn run_timers(&self, now: Instant) {
+        while let Some(deadline) = self.next_timeout() {
+            if deadline > now {
+                break;
+            }
+            // Remove the timer and get the token
+            let token = self.timer_queue.lock().unwrap().pop().unwrap().token();
+            if let Ok(mut handler_borrow) = self.handler.try_borrow_mut() {
+                handler_borrow.timer(token);
+            }
+        }
+    }
 }
 
 impl Buffers {
@@ -1339,12 +1365,14 @@ impl WindowHandle {
         Text::new()
     }
 
-    pub fn request_timer(&self, _deadline: std::time::Instant) -> TimerToken {
-        // TODO(x11/timers): implement WindowHandle::request_timer
-        //     This one might be tricky, since there's not really any timers to hook into in X11.
-        //     Might have to code up our own Timer struct, running in its own thread?
-        log::warn!("WindowHandle::resizeable is currently unimplemented for X11 platforms.");
-        TimerToken::INVALID
+    pub fn request_timer(&self, deadline: Instant) -> TimerToken {
+        if let Some(w) = self.window.upgrade() {
+            let timer = Timer::new(deadline);
+            w.timer_queue.lock().unwrap().push(timer);
+            timer.token()
+        } else {
+            TimerToken::INVALID
+        }
     }
 
     pub fn set_cursor(&mut self, _cursor: &Cursor) {
