refactor(windows): Monitor.id is the shared MonitorId, with the same JSON

Monitor.id was an isize HMONITOR; it is now komorebi_backend::MonitorId (the
type WindowsBackend::monitors already returned). A serde adapter
(hmonitor_json) writes it with serialize_i64(to_hmonitor()) and reads an isize
through from_hmonitor, bit for bit, so the JSON is the same plain number as
before (including negative handles); the schemars schema is declared as isize.
serial_number_id was already Option<String> (the shared shape), so it is
unchanged. monitor::new / Monitor::new keep an isize parameter (every caller
passes an HMONITOR); the 12 uses that need the raw handle call
.to_hmonitor() (WindowsApi::monitor, wallpaper, DPI, zoomed checks, ids
compared with monitor_from_window/point). MonitorInformation.id stays isize.

BEHAVIOUR (JSON-identical by construction, not proven by running): the new
unit tests of the previous revision pin the JSON against a real capture,
but the Windows crate's tests cannot run on this host. Gate needed: any
e2e scenario that reads komorebic state or saves/loads it, and monitor
reconciliation / unknown_monitor. Verified: Windows clippy -D warnings via
tools/fast-check PASS.

komorebi/src/border_manager/mod.rs

@@ -741,8 +741,8 @@ pub fn handle_notifications(wm: Arc<Mutex<WindowManager>>) -> color_eyre::Result
                         let foreground_hwnd = WindowsApi::foreground_window().unwrap_or_default();
                         let foreground_monitor_id =
                             WindowsApi::monitor_from_window(foreground_hwnd);
-                        let is_maximized =
-                            foreground_monitor_id == m.id && WindowsApi::is_zoomed(foreground_hwnd);
+                        let is_maximized = foreground_monitor_id == m.id.to_hmonitor()
+                            && WindowsApi::is_zoomed(foreground_hwnd);
 
                         if is_maximized {
                             tracing::trace!(

komorebi/src/monitor.rs

@@ -13,6 +13,7 @@ use crate::border_manager::BORDER_OFFSET;
 use crate::border_manager::BORDER_WIDTH;
 use crate::core::Rect;
 use crate::windows_backend::backend;
+use komorebi_backend::MonitorId;
 use komorebi_backend::WindowId;
 
 use crate::DEFAULT_CONTAINER_PADDING;
@@ -29,10 +30,28 @@ use crate::workspace::Workspace;
 use crate::workspace::WorkspaceGlobals;
 use crate::workspace::WorkspaceLayer;
 
+/// `Monitor::id` is a `MonitorId` in Rust and the same plain JSON number as the `isize` handle it
+/// was before: `komorebic state` and the saved state files do not change.
+mod hmonitor_json {
+    use komorebi_backend::MonitorId;
+    use serde::Deserialize;
+    use serde::Deserializer;
+    use serde::Serializer;
+
+    pub fn serialize<S: Serializer>(id: &MonitorId, serializer: S) -> Result<S::Ok, S::Error> {
+        serializer.serialize_i64(id.to_hmonitor() as i64)
+    }
+
+    pub fn deserialize<'de, D: Deserializer<'de>>(deserializer: D) -> Result<MonitorId, D::Error> {
+        Ok(MonitorId::from_hmonitor(isize::deserialize(deserializer)?))
+    }
+}
 #[derive(Debug, Clone, Serialize, Deserialize, PartialEq)]
 #[cfg_attr(feature = "schemars", derive(schemars::JsonSchema))]
 pub struct Monitor {
-    pub id: isize,
+    #[serde(with = "hmonitor_json")]
+    #[cfg_attr(feature = "schemars", schemars(with = "isize"))]
+    pub id: MonitorId,
     pub name: String,
     pub device: String,
     pub device_id: String,
@@ -67,7 +86,7 @@ pub struct MonitorInformation {
 impl From<&Monitor> for MonitorInformation {
     fn from(monitor: &Monitor) -> Self {
         Self {
-            id: monitor.id,
+            id: monitor.id.to_hmonitor(),
             name: monitor.name.clone(),
             device: monitor.device.clone(),
             device_id: monitor.device_id.clone(),
@@ -90,7 +109,7 @@ pub fn new(
     workspaces.elements_mut().push_back(Workspace::default());
 
     Monitor {
-        id,
+        id: MonitorId::from_hmonitor(id),
         name,
         device,
         device_id,
@@ -133,7 +152,7 @@ impl Monitor {
 
     pub fn placeholder() -> Self {
         Self {
-            id: 0,
+            id: MonitorId(0),
             name: "PLACEHOLDER".to_string(),
             device: "".to_string(),
             device_id: "".to_string(),
@@ -171,7 +190,7 @@ impl Monitor {
 
     pub fn load_focused_workspace(&mut self, mouse_follows_focus: bool) -> eyre::Result<()> {
         let focused_idx = self.focused_workspace_idx();
-        let hmonitor = self.id;
+        let hmonitor = self.id.to_hmonitor();
         let monitor_wp = self.wallpaper.clone();
         for (i, workspace) in self.workspaces_mut().iter_mut().enumerate() {
             if i == focused_idx {

komorebi/src/monitor_reconciliator/mod.rs

@@ -293,7 +293,7 @@ where
                     let mut should_update = false;
 
                     // Update work areas as necessary
-                    if let Ok(reference) = WindowsApi::monitor(monitor.id)
+                    if let Ok(reference) = WindowsApi::monitor(monitor.id.to_hmonitor())
                         && reference.work_area_size != monitor.work_area_size
                     {
                         monitor.work_area_size = Rect {
@@ -325,7 +325,7 @@ where
                     let mut should_update = false;
 
                     // Update sizes and work areas as necessary
-                    if let Ok(reference) = WindowsApi::monitor(monitor.id) {
+                    if let Ok(reference) = WindowsApi::monitor(monitor.id.to_hmonitor()) {
                         if reference.work_area_size != monitor.work_area_size {
                             monitor.work_area_size = Rect {
                                 left: reference.work_area_size.left,
@@ -1275,7 +1275,7 @@ mod tests {
             assert_eq!(monitors.len(), 1, "Expected one monitor");
 
             // hmonitor
-            assert_eq!(monitors[0].id, 1);
+            assert_eq!(monitors[0].id.to_hmonitor(), 1);
 
             // device name
             assert_eq!(monitors[0].name, String::from("DISPLAY1"));

komorebi/src/window_manager.rs

@@ -771,7 +771,7 @@ impl WindowManager {
             let focused_workspace_idx = monitor.focused_workspace_idx();
             monitor.update_workspace_globals(focused_workspace_idx, offset);
 
-            let hmonitor = monitor.id;
+            let hmonitor = monitor.id.to_hmonitor();
             let monitor_wp = monitor.wallpaper.clone();
             let workspace = monitor
                 .focused_workspace_mut()
@@ -1572,7 +1572,7 @@ impl WindowManager {
             .get_mut(monitor_idx)
             .ok_or_eyre("there is no monitor")?;
 
-        let hmonitor = monitor.id;
+        let hmonitor = monitor.id.to_hmonitor();
         let monitor_wp = monitor.wallpaper.clone();
 
         let workspace = monitor
@@ -2589,12 +2589,14 @@ impl WindowManager {
                 let a = self
                     .focused_monitor()
                     .ok_or_eyre("there is no monitor focused monitor")?
-                    .id;
+                    .id
+                    .to_hmonitor();
                 let b = self
                     .monitors_mut()
                     .get_mut(origin_monitor_idx)
                     .ok_or_eyre("there is no monitor at this index")?
-                    .id;
+                    .id
+                    .to_hmonitor();
 
                 if !WindowsApi::monitors_have_same_dpi(a, b)? {
                     self.update_focused_workspace(self.mouse_follows_focus, true)?;
@@ -3766,7 +3768,7 @@ impl WindowManager {
         let hmonitor = WindowsApi::monitor_from_window(window.hwnd);
 
         for (i, monitor) in self.monitors().iter().enumerate() {
-            if monitor.id == hmonitor {
+            if monitor.id.to_hmonitor() == hmonitor {
                 return Option::from(i);
             }
         }
@@ -3789,7 +3791,7 @@ impl WindowManager {
         let hmonitor = WindowsApi::monitor_from_point(WindowsApi::cursor_pos().ok()?);
 
         for (i, monitor) in self.monitors().iter().enumerate() {
-            if monitor.id == hmonitor {
+            if monitor.id.to_hmonitor() == hmonitor {
                 return Option::from(i);
             }
         }

komorebi/src/windows_backend.rs

@@ -110,7 +110,7 @@ impl Backend for WindowsBackend {
             .map(|(_, hmonitor)| {
                 let monitor = WindowsApi::monitor(hmonitor).map_err(platform)?;
                 Ok(MonitorInfo {
-                    id: MonitorId::from_hmonitor(monitor.id),
+                    id: monitor.id,
                     size: monitor.size,
                     work_area: monitor.work_area_size,
                     name: Some(monitor.name),