Add multi-window support

Previously Alacritty would always initialize only a single terminal
emulator window feeding into the winit event loop, however some
platforms like macOS expect all windows to be spawned by the same
process and this "daemon-mode" can also come with the advantage of
increased memory efficiency.

The event loop has been restructured to handle all window-specific
events only by the event processing context with the associated window
id. This makes it possible to add new terminal windows at any time using
the WindowContext::new function call.

Some preliminary tests have shown that for empty terminals, this reduces
the cost of additional terminal emulators from ~100M to ~6M. However at
this point the robustness of the daemon against issues with individual
terminals has not been refined, making the reliability of this system
questionable.

New windows can be created either by using the new `CreateNewWindow`
action, or with the `alacritty msg create-window` subcommand. The
subcommand sends a message to an IPC socket which Alacritty listens on,
its location can be found in the `ALACRITTY_SOCKET` environment
variable.

Fixes #607.

1 files changed, 37 insertions, 32 deletions

diff --git a/alacritty/src/scheduler.rs b/alacritty/src/scheduler.rs
index 5e454141..924f5904 100644
--- a/alacritty/src/scheduler.rs
+++ b/alacritty/src/scheduler.rs
@@ -3,15 +3,27 @@
 use std::collections::VecDeque;
 use std::time::{Duration, Instant};
 
-use glutin::event::Event as GlutinEvent;
+use glutin::event_loop::EventLoopProxy;
+use glutin::window::WindowId;
 
-use crate::event::Event as AlacrittyEvent;
-
-type Event = GlutinEvent<'static, AlacrittyEvent>;
+use crate::event::Event;
 
 /// ID uniquely identifying a timer.
 #[derive(Copy, Clone, Debug, PartialEq, Eq)]
-pub enum TimerId {
+pub struct TimerId {
+    topic: Topic,
+    window_id: WindowId,
+}
+
+impl TimerId {
+    pub fn new(topic: Topic, window_id: WindowId) -> Self {
+        Self { topic, window_id }
+    }
+}
+
+/// Available timer topics.
+#[derive(Copy, Clone, Debug, PartialEq, Eq)]
+pub enum Topic {
     SelectionScrolling,
     DelayedSearch,
     BlinkCursor,
@@ -21,33 +33,29 @@ pub enum TimerId {
 pub struct Timer {
     pub deadline: Instant,
     pub event: Event,
+    pub id: TimerId,
 
     interval: Option<Duration>,
-    id: TimerId,
 }
 
 /// Scheduler tracking all pending timers.
 pub struct Scheduler {
     timers: VecDeque<Timer>,
-}
-
-impl Default for Scheduler {
-    fn default() -> Self {
-        Self { timers: VecDeque::new() }
-    }
+    event_proxy: EventLoopProxy<Event>,
 }
 
 impl Scheduler {
-    pub fn new() -> Self {
-        Self::default()
+    pub fn new(event_proxy: EventLoopProxy<Event>) -> Self {
+        Self { timers: VecDeque::new(), event_proxy }
     }
 
     /// Process all pending timers.
     ///
     /// If there are still timers pending after all ready events have been processed, the closest
     /// pending deadline will be returned.
-    pub fn update(&mut self, event_queue: &mut Vec<Event>) -> Option<Instant> {
+    pub fn update(&mut self) -> Option<Instant> {
         let now = Instant::now();
+
         while !self.timers.is_empty() && self.timers[0].deadline <= now {
             if let Some(timer) = self.timers.pop_front() {
                 // Automatically repeat the event.
@@ -55,7 +63,7 @@ impl Scheduler {
                     self.schedule(timer.event.clone(), interval, true, timer.id);
                 }
 
-                event_queue.push(timer.event);
+                let _ = self.event_proxy.send_event(timer.event);
             }
         }
 
@@ -67,17 +75,11 @@ impl Scheduler {
         let deadline = Instant::now() + interval;
 
         // Get insert position in the schedule.
-        let mut index = self.timers.len();
-        loop {
-            if index == 0 {
-                break;
-            }
-            index -= 1;
-
-            if self.timers[index].deadline < deadline {
-                break;
-            }
-        }
+        let index = self
+            .timers
+            .iter()
+            .position(|timer| timer.deadline > deadline)
+            .unwrap_or_else(|| self.timers.len());
 
         // Set the automatic event repeat rate.
         let interval = if repeat { Some(interval) } else { None };
@@ -86,9 +88,9 @@ impl Scheduler {
     }
 
     /// Cancel a scheduled event.
-    pub fn unschedule(&mut self, id: TimerId) -> Option<Event> {
+    pub fn unschedule(&mut self, id: TimerId) -> Option<Timer> {
         let index = self.timers.iter().position(|timer| timer.id == id)?;
-        self.timers.remove(index).map(|timer| timer.event)
+        self.timers.remove(index)
     }
 
     /// Check if a timer is already scheduled.
@@ -96,8 +98,11 @@ impl Scheduler {
         self.timers.iter().any(|timer| timer.id == id)
     }
 
-    /// Access a staged event by ID.
-    pub fn get_mut(&mut self, id: TimerId) -> Option<&mut Timer> {
-        self.timers.iter_mut().find(|timer| timer.id == id)
+    /// Remove all timers scheduled for a window.
+    ///
+    /// This must be called when a window is removed to ensure that timers on intervals do not
+    /// stick around forever and cause a memory leak.
+    pub fn unschedule_window(&mut self, window_id: WindowId) {
+        self.timers.retain(|timer| timer.id.window_id != window_id);
     }
 }