Major module refactor (#19)

* refactor: major module restructuring

Modules now implement a "controller", which allows for separation of logic from UI code and enforces a tighter structure around how modules should be written. The introduction of this change required major refactoring or even rewriting of all modules.

This also better integrates the popup into modules, making it easier for data to be passed around without fetching the same thing twice

The refactor also improves some client code, switching from `ksway` to the much more stable `swayipc-async`. Partial multi-monitor for the tray module has been added.

BREAKING CHANGE: The `mpd` module config has changed, moving the icons to their own object.

src/bridge_channel.rs

@@ -0,0 +1,43 @@
+use tokio::spawn;
+use tokio::sync::mpsc;
+
+/// MPSC async -> sync channel.
+/// The sender uses `tokio::sync::mpsc`
+/// while the receiver uses `glib::MainContext::channel`.
+///
+/// This makes it possible to send events asynchronously
+/// and receive them on the main thread,
+/// allowing UI updates to be handled on the receiving end.
+pub struct BridgeChannel<T> {
+    async_tx: mpsc::Sender<T>,
+    sync_rx: glib::Receiver<T>,
+}
+
+impl<T: Send + 'static> BridgeChannel<T> {
+    /// Creates a new channel
+    pub fn new() -> Self {
+        let (async_tx, mut async_rx) = mpsc::channel(32);
+        let (sync_tx, sync_rx) = glib::MainContext::channel(glib::PRIORITY_DEFAULT);
+
+        spawn(async move {
+            while let Some(val) = async_rx.recv().await {
+                sync_tx.send(val).expect("Failed to send message");
+            }
+        });
+
+        Self { async_tx, sync_rx }
+    }
+
+    /// Gets a clone of the sender.
+    pub fn create_sender(&self) -> mpsc::Sender<T> {
+        self.async_tx.clone()
+    }
+
+    /// Attaches a callback to the receiver.
+    pub fn recv<F>(self, f: F) -> glib::SourceId
+    where
+        F: FnMut(T) -> glib::Continue + 'static,
+    {
+        self.sync_rx.attach(None, f)
+    }
+}