feat(wm): add workspace reconciliator module

This commit adds the workspace_reconciliator module which uses a tightly
bounded channel (cap: 1) to update the focused workspace in situations
where the user or another process has foregrounded a window that is on a
different workspace.

This most often happens via Alt-Tab, or by clicking a link which opens
in another application.

workspace_reconciliator::Notification contains the target monitor and
workspace indices, which when received allows for the correct workspace to
be focused.

These notifications are sent in process_event.rs when handling
WindowManagerEvent::Show, Manage and Uncloak events.

All previous logic pertaining to workspace reconciliation which lived in
the handler for these events has been removed and replaced with
notifications sent to the reconciliator.

As the notifications channel is tightly capped and any notifications
which overflow the cap will never be delivered, we are able to avoid the
infinite workspace switching loops which happened when using the
previous logic, which ran on every single event.

komorebi/src/lib.rs

@@ -21,6 +21,7 @@ pub mod windows_callbacks;
 pub mod winevent;
 pub mod winevent_listener;
 pub mod workspace;
+pub mod workspace_reconciliator;
 
 use lazy_static::lazy_static;
 use std::collections::HashMap;

komorebi/src/main.rs

@@ -34,6 +34,7 @@ use komorebi::static_config::StaticConfig;
 use komorebi::window_manager::WindowManager;
 use komorebi::windows_api::WindowsApi;
 use komorebi::winevent_listener;
+use komorebi::workspace_reconciliator;
 use komorebi::CUSTOM_FFM;
 use komorebi::DATA_DIR;
 use komorebi::HOME_DIR;
@@ -255,6 +256,7 @@ fn main() -> Result<()> {
     }
 
     border_manager::listen_for_notifications(wm.clone());
+    workspace_reconciliator::listen_for_notifications(wm.clone());
 
     let (ctrlc_sender, ctrlc_receiver) = crossbeam_channel::bounded(1);
     ctrlc::set_handler(move || {

komorebi/src/process_event.rs

@@ -22,6 +22,7 @@ use crate::window_manager::WindowManager;
 use crate::window_manager_event::WindowManagerEvent;
 use crate::windows_api::WindowsApi;
 use crate::winevent::WinEvent;
+use crate::workspace_reconciliator;
 use crate::Notification;
 use crate::NotificationEvent;
 use crate::DATA_DIR;
@@ -259,74 +260,70 @@ impl WindowManager {
             WindowManagerEvent::Show(_, window)
             | WindowManagerEvent::Manage(window)
             | WindowManagerEvent::Uncloak(_, window) => {
-                let mut switch_to = None;
+                let focused_monitor_idx = self.focused_monitor_idx();
+                let focused_workspace_idx =
+                    self.focused_workspace_idx_for_monitor_idx(focused_monitor_idx)?;
+
+                let focused_pair = (focused_monitor_idx, focused_workspace_idx);
+
+                let mut needs_reconciliation = false;
+
                 for (i, monitors) in self.monitors().iter().enumerate() {
                     for (j, workspace) in monitors.workspaces().iter().enumerate() {
                         if workspace.contains_window(window.hwnd) {
-                            switch_to = Some((i, j));
+                            if focused_pair != (i, j) {
+                                workspace_reconciliator::event_tx().send(
+                                    workspace_reconciliator::Notification {
+                                        monitor_idx: i,
+                                        workspace_idx: j,
+                                    },
+                                )?;
+
+                                needs_reconciliation = true;
+                            }
                         }
                     }
                 }
 
-                match switch_to {
-                    Some((known_monitor_idx, known_workspace_idx)) => {
-                        if !matches!(event, WindowManagerEvent::Uncloak(_, _)) {
-                            if self.focused_monitor_idx() != known_monitor_idx
-                                || self
-                                    .focused_monitor()
-                                    .ok_or_else(|| anyhow!("there is no monitor"))?
-                                    .focused_workspace_idx()
-                                    != known_workspace_idx
-                            {
-                                self.focus_monitor(known_monitor_idx)?;
-                                self.focus_workspace(known_workspace_idx)?;
-                            }
-                        }
-                    }
-                    None => {
-                        // There are some applications such as Firefox where, if they are focused when a
-                        // workspace switch takes place, it will fire an additional Show event, which will
-                        // result in them being associated with both the original workspace and the workspace
-                        // being switched to. This loop is to try to ensure that we don't end up with
-                        // duplicates across multiple workspaces, as it results in ghost layout tiles.
-                        let mut proceed = true;
+                // There are some applications such as Firefox where, if they are focused when a
+                // workspace switch takes place, it will fire an additional Show event, which will
+                // result in them being associated with both the original workspace and the workspace
+                // being switched to. This loop is to try to ensure that we don't end up with
+                // duplicates across multiple workspaces, as it results in ghost layout tiles.
+                let mut proceed = true;
 
-                        for (i, monitor) in self.monitors().iter().enumerate() {
-                            for (j, workspace) in monitor.workspaces().iter().enumerate() {
-                                if workspace.container_for_window(window.hwnd).is_some()
-                                    && i != self.focused_monitor_idx()
-                                    && j != monitor.focused_workspace_idx()
-                                {
-                                    tracing::debug!(
+                for (i, monitor) in self.monitors().iter().enumerate() {
+                    for (j, workspace) in monitor.workspaces().iter().enumerate() {
+                        if workspace.container_for_window(window.hwnd).is_some()
+                            && i != self.focused_monitor_idx()
+                            && j != monitor.focused_workspace_idx()
+                        {
+                            tracing::debug!(
                                 "ignoring show event for window already associated with another workspace"
                             );
 
-                                    window.hide();
-                                    proceed = false;
-                                }
-                            }
+                            window.hide();
+                            proceed = false;
                         }
+                    }
+                }
 
-                        if proceed {
-                            let behaviour = self.window_container_behaviour;
-                            let workspace = self.focused_workspace_mut()?;
+                if proceed {
+                    let behaviour = self.window_container_behaviour;
+                    let workspace = self.focused_workspace_mut()?;
 
-                            if !workspace.contains_window(window.hwnd) && switch_to.is_none() {
-                                match behaviour {
-                                    WindowContainerBehaviour::Create => {
-                                        workspace.new_container_for_window(window);
-                                        self.update_focused_workspace(false, false)?;
-                                    }
-                                    WindowContainerBehaviour::Append => {
-                                        workspace
-                                            .focused_container_mut()
-                                            .ok_or_else(|| {
-                                                anyhow!("there is no focused container")
-                                            })?
-                                            .add_window(window);
-                                        self.update_focused_workspace(true, false)?;
-                                    }
-                                }
+                    if !workspace.contains_window(window.hwnd) && !needs_reconciliation {
+                        match behaviour {
+                            WindowContainerBehaviour::Create => {
+                                workspace.new_container_for_window(window);
+                                self.update_focused_workspace(false, false)?;
+                            }
+                            WindowContainerBehaviour::Append => {
+                                workspace
+                                    .focused_container_mut()
+                                    .ok_or_else(|| anyhow!("there is no focused container"))?
+                                    .add_window(window);
+                                self.update_focused_workspace(true, false)?;
                             }
                         }
                     }

komorebi/src/workspace_reconciliator.rs

@@ -0,0 +1,56 @@
+use crate::WindowManager;
+use crossbeam_channel::Receiver;
+use crossbeam_channel::Sender;
+use parking_lot::Mutex;
+use std::sync::Arc;
+use std::sync::OnceLock;
+
+#[derive(Copy, Clone)]
+pub struct Notification {
+    pub monitor_idx: usize,
+    pub workspace_idx: usize,
+}
+
+static CHANNEL: OnceLock<(Sender<Notification>, Receiver<Notification>)> = OnceLock::new();
+
+pub fn channel() -> &'static (Sender<Notification>, Receiver<Notification>) {
+    CHANNEL.get_or_init(|| crossbeam_channel::bounded(1))
+}
+
+pub fn event_tx() -> Sender<Notification> {
+    channel().0.clone()
+}
+
+pub fn event_rx() -> Receiver<Notification> {
+    channel().1.clone()
+}
+
+pub fn listen_for_notifications(wm: Arc<Mutex<WindowManager>>) {
+    tracing::info!("listening");
+    let receiver = event_rx();
+
+    std::thread::spawn(move || -> color_eyre::Result<()> {
+        for notification in receiver {
+            tracing::info!("running reconciliation");
+            let mut wm = wm.lock();
+            let focused_monitor_idx = wm.focused_monitor_idx();
+            let focused_workspace_idx =
+                wm.focused_workspace_idx_for_monitor_idx(focused_monitor_idx)?;
+
+            let focused_pair = (focused_monitor_idx, focused_workspace_idx);
+            let updated_pair = (notification.monitor_idx, notification.workspace_idx);
+
+            if focused_pair != updated_pair {
+                wm.focus_monitor(notification.monitor_idx)?;
+                let mouse_follows_focus = wm.mouse_follows_focus;
+
+                if let Some(monitor) = wm.focused_monitor_mut() {
+                    monitor.focus_workspace(notification.workspace_idx)?;
+                    monitor.load_focused_workspace(mouse_follows_focus)?;
+                }
+            }
+        }
+
+        Ok(())
+    });
+}