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, 47 insertions, 4 deletions

diff --git a/alacritty/src/cli.rs b/alacritty/src/cli.rs
index b1e12007..ce0563ff 100644
--- a/alacritty/src/cli.rs
+++ b/alacritty/src/cli.rs
@@ -10,7 +10,7 @@ use alacritty_terminal::config::Program;
 use crate::config::window::{Class, DEFAULT_NAME};
 use crate::config::{serde_utils, Config};
 
-/// Options specified on the command line.
+/// CLI options for the main Alacritty executable.
 #[derive(StructOpt, Debug)]
 #[structopt(author, about, version = env!("VERSION"))]
 pub struct Options {
@@ -57,9 +57,10 @@ pub struct Options {
     #[structopt(long)]
     pub hold: bool,
 
-    /// CLI options for config overrides.
-    #[structopt(skip)]
-    pub config_options: Value,
+    /// Path for IPC socket creation.
+    #[cfg(unix)]
+    #[structopt(long)]
+    pub socket: Option<PathBuf>,
 
     /// Reduces the level of verbosity (the min level is -qq).
     #[structopt(short, conflicts_with("verbose"), parse(from_occurrences))]
@@ -76,6 +77,15 @@ pub struct Options {
     /// Override configuration file options [example: cursor.style=Beam].
     #[structopt(short = "o", long)]
     option: Vec<String>,
+
+    /// CLI options for config overrides.
+    #[structopt(skip)]
+    pub config_options: Value,
+
+    /// Subcommand passed to the CLI.
+    #[cfg(unix)]
+    #[structopt(subcommand)]
+    pub subcommands: Option<Subcommands>,
 }
 
 impl Options {
@@ -118,6 +128,11 @@ impl Options {
             config.ui_config.window.class = class.clone();
         }
 
+        #[cfg(unix)]
+        {
+            config.ui_config.ipc_socket |= self.socket.is_some();
+        }
+
         config.ui_config.window.dynamic_title &= self.title.is_none();
         config.ui_config.window.embed = self.embed.as_ref().and_then(|embed| embed.parse().ok());
         config.ui_config.debug.print_events |= self.print_events;
@@ -199,6 +214,34 @@ fn parse_class(input: &str) -> Result<Class, String> {
     }
 }
 
+/// Available CLI subcommands.
+#[cfg(unix)]
+#[derive(StructOpt, Debug)]
+pub enum Subcommands {
+    Msg(MessageOptions),
+}
+
+/// Send a message to the Alacritty socket.
+#[cfg(unix)]
+#[derive(StructOpt, Debug)]
+pub struct MessageOptions {
+    /// IPC socket connection path override.
+    #[structopt(long, short)]
+    pub socket: Option<PathBuf>,
+
+    /// Message which should be sent.
+    #[structopt(subcommand)]
+    pub message: SocketMessage,
+}
+
+/// Available socket messages.
+#[cfg(unix)]
+#[derive(StructOpt, Debug)]
+pub enum SocketMessage {
+    /// Create a new window in the same Alacritty process.
+    CreateWindow,
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;