Implement by-id workspace action addressing

It's not added to clap because there's no convenient mutually-exclusive
argument enum derive yet (to have either the current <REFERENCE> or an
--id <ID>). It's not added to config parsing because I don't see how it
could be useful there. As such, it's only accessible through raw IPC.

niri-config/src/lib.rs

@@ -1233,6 +1233,7 @@ impl From<niri_ipc::Action> for Action {
 
 #[derive(Debug, PartialEq, Eq, Clone)]
 pub enum WorkspaceReference {
+    Id(u64),
     Index(u8),
     Name(String),
 }
@@ -1240,6 +1241,7 @@ pub enum WorkspaceReference {
 impl From<WorkspaceReferenceArg> for WorkspaceReference {
     fn from(reference: WorkspaceReferenceArg) -> WorkspaceReference {
         match reference {
+            WorkspaceReferenceArg::Id(id) => Self::Id(id),
             WorkspaceReferenceArg::Index(i) => Self::Index(i),
             WorkspaceReferenceArg::Name(n) => Self::Name(n),
         }

niri-ipc/src/lib.rs

@@ -308,10 +308,12 @@ pub enum SizeChange {
     AdjustProportion(f64),
 }
 
-/// Workspace reference (index or name) to operate on.
+/// Workspace reference (id, index or name) to operate on.
 #[derive(Serialize, Deserialize, Debug, Clone, PartialEq, Eq)]
 #[cfg_attr(feature = "json-schema", derive(schemars::JsonSchema))]
 pub enum WorkspaceReferenceArg {
+    /// Id of the workspace.
+    Id(u64),
     /// Index of the workspace.
     Index(u8),
     /// Name of the workspace.

src/layout/mod.rs

@@ -836,6 +836,32 @@ impl<W: LayoutElement> Layout<W> {
         None
     }
 
+    pub fn find_workspace_by_id(&self, id: WorkspaceId) -> Option<(usize, &Workspace<W>)> {
+        match &self.monitor_set {
+            MonitorSet::Normal { ref monitors, .. } => {
+                for mon in monitors {
+                    if let Some((index, workspace)) = mon
+                        .workspaces
+                        .iter()
+                        .enumerate()
+                        .find(|(_, w)| w.id() == id)
+                    {
+                        return Some((index, workspace));
+                    }
+                }
+            }
+            MonitorSet::NoOutputs { workspaces } => {
+                if let Some((index, workspace)) =
+                    workspaces.iter().enumerate().find(|(_, w)| w.id() == id)
+                {
+                    return Some((index, workspace));
+                }
+            }
+        }
+
+        None
+    }
+
     pub fn find_workspace_by_name(&self, workspace_name: &str) -> Option<(usize, &Workspace<W>)> {
         match &self.monitor_set {
             MonitorSet::Normal { ref monitors, .. } => {

src/layout/workspace.rs

@@ -133,6 +133,10 @@ impl WorkspaceId {
     pub fn get(self) -> u64 {
         self.0
     }
+
+    pub fn specific(id: u64) -> Self {
+        Self(id)
+    }
 }
 
 niri_render_elements! {

src/niri.rs

@@ -115,6 +115,7 @@ use crate::input::{
     apply_libinput_settings, mods_with_finger_scroll_binds, mods_with_wheel_binds, TabletData,
 };
 use crate::ipc::server::IpcServer;
+use crate::layout::workspace::WorkspaceId;
 use crate::layout::{Layout, LayoutElement as _, MonitorRenderElement};
 use crate::protocols::foreign_toplevel::{self, ForeignToplevelManagerState};
 use crate::protocols::gamma_control::GammaControlManagerState;
@@ -2422,16 +2423,17 @@ impl Niri {
         &self,
         workspace_reference: WorkspaceReference,
     ) -> Option<(Option<Output>, usize)> {
-        let workspace_name = match workspace_reference {
+        let (target_workspace_index, target_workspace) = match workspace_reference {
             WorkspaceReference::Index(index) => {
                 return Some((None, index.saturating_sub(1) as usize));
             }
-            WorkspaceReference::Name(name) => name,
+            WorkspaceReference::Name(name) => self.layout.find_workspace_by_name(&name)?,
+            WorkspaceReference::Id(id) => {
+                let id = WorkspaceId::specific(id);
+                self.layout.find_workspace_by_id(id)?
+            }
         };
 
-        let (target_workspace_index, target_workspace) =
-            self.layout.find_workspace_by_name(&workspace_name)?;
-
         // FIXME: when we do fixes for no connected outputs, this will need fixing too.
         let active_workspace = self.layout.active_workspace()?;