Clarify constructor failures and borrowed API contracts

crates/ferese-core/src/focus.rs

@@ -50,11 +50,13 @@ pub struct FocusCycle {
 }
 
 impl FocusCycle {
+    #[must_use]
     pub fn new(windows: Vec<WindowId>, current: Option<WindowId>) -> Self {
         let selected = current.filter(|id| windows.contains(id));
         Self { windows, selected }
     }
 
+    #[must_use]
     pub fn windows(&self) -> &[WindowId] {
         &self.windows
     }

crates/ferese-core/src/output.rs

@@ -16,6 +16,7 @@ pub struct OutputGeometry {
 }
 
 impl OutputGeometry {
+    #[must_use]
     pub const fn new(x: i32, y: i32, width: i32, height: i32) -> Self {
         Self {
             x,
@@ -223,6 +224,7 @@ impl OutputWorkspaceMap {
         })
     }
 
+    #[must_use]
     pub fn assigned_workspaces(
         &self,
         output: OutputId,
@@ -233,22 +235,27 @@ impl OutputWorkspaceMap {
             .flat_map(|state| state.workspaces.iter().copied())
     }
 
+    #[must_use]
     pub fn focused_output(&self) -> Option<OutputId> {
         self.focused
     }
 
+    #[must_use]
     pub fn active_workspace(&self, output: OutputId) -> Option<WorkspaceId> {
         self.outputs.get(&output).map(|state| state.active)
     }
 
+    #[must_use]
     pub fn previous_workspace(&self, output: OutputId) -> Option<WorkspaceId> {
         self.outputs.get(&output).and_then(|state| state.previous)
     }
 
+    #[must_use]
     pub fn output_for_workspace(&self, workspace: WorkspaceId) -> Option<OutputId> {
         self.assignments.get(&workspace).copied()
     }
 
+    #[must_use]
     pub fn home_output(&self, workspace: WorkspaceId) -> Option<OutputId> {
         self.homes.get(&workspace).copied()
     }
@@ -295,6 +302,7 @@ impl OutputWorkspaceMap {
         self.outputs.keys().copied()
     }
 
+    #[must_use]
     pub fn geometry(&self, output: OutputId) -> Option<OutputGeometry> {
         self.outputs.get(&output).map(|state| state.geometry)
     }

crates/ferese-core/src/workspace.rs

@@ -39,6 +39,7 @@ impl Default for WorkspaceLayout {
 }
 
 impl WorkspaceLayout {
+    #[must_use]
     pub fn new(
         mode: LayoutMode,
         default_column_width: ColumnWidth,
@@ -61,6 +62,7 @@ impl WorkspaceLayout {
         self
     }
 
+    #[must_use]
     pub fn mode(&self) -> LayoutMode {
         match self {
             Self::Scrolling(_) => LayoutMode::Scrolling,
@@ -68,6 +70,7 @@ impl WorkspaceLayout {
         }
     }
 
+    #[must_use]
     pub fn viewport_x(&self) -> Option<f64> {
         match self {
             Self::Scrolling(layout) => Some(layout.viewport_x()),
@@ -75,6 +78,7 @@ impl WorkspaceLayout {
         }
     }
 
+    #[must_use]
     pub fn preferred_window(&self) -> Option<WindowId> {
         match self {
             Self::Scrolling(layout) => layout.active_window(),
@@ -82,6 +86,7 @@ impl WorkspaceLayout {
         }
     }
 
+    #[must_use]
     pub fn contains(&self, window: WindowId) -> bool {
         match self {
             Self::Scrolling(layout) => layout.contains(window),
@@ -125,6 +130,7 @@ impl WorkspaceLayout {
         }
     }
 
+    #[must_use]
     pub fn tab_group(&self, window: WindowId) -> Option<ferese_layout::TabGroup> {
         match self {
             Self::Tree(tree) => tree.tab_group(window),
@@ -132,6 +138,7 @@ impl WorkspaceLayout {
         }
     }
 
+    #[must_use]
     pub fn adjacent_tab(&self, window: WindowId, previous: bool) -> Option<WindowId> {
         match self {
             Self::Tree(tree) => tree.adjacent_tab(window, previous),
@@ -445,6 +452,7 @@ impl Default for WorkspaceSet {
 }
 
 impl WorkspaceSet {
+    #[must_use]
     pub fn new(
         default_layout_mode: LayoutMode,
         default_column_width: ColumnWidth,
@@ -562,10 +570,12 @@ impl WorkspaceSet {
         }
     }
 
+    #[must_use]
     pub fn active_id(&self) -> WorkspaceId {
         self.active
     }
 
+    #[must_use]
     pub fn active(&self) -> &Workspace {
         self.workspaces
             .get(&self.active)
@@ -596,6 +606,7 @@ impl WorkspaceSet {
         Ok(visible_floating.or(self.active().fullscreen).or(focused))
     }
 
+    #[must_use]
     pub fn workspace(&self, id: WorkspaceId) -> Option<&Workspace> {
         self.workspaces.get(&id)
     }
@@ -608,10 +619,12 @@ impl WorkspaceSet {
         self.workspaces.values()
     }
 
+    #[must_use]
     pub fn workspace_for_window(&self, window: WindowId) -> Option<WorkspaceId> {
         self.window_workspaces.get(&window).copied()
     }
 
+    #[must_use]
     pub fn placement(&self, window: WindowId) -> Option<WindowPlacement> {
         self.placements.get(&window).copied()
     }
@@ -823,6 +836,7 @@ impl WorkspaceSet {
     }
 
     /// Reserve workspace identities in a pure topology plan without creating them.
+    #[must_use]
     pub fn next_workspace_id(&self) -> WorkspaceId {
         WorkspaceId(self.next_id)
     }
@@ -1210,10 +1224,12 @@ fn finite_or_zero(value: f64) -> f64 {
 }
 
 impl Workspace {
+    #[must_use]
     pub fn window_count(&self) -> usize {
         self.layout.window_ids().count() + self.floating.len()
     }
 
+    #[must_use]
     pub fn is_empty(&self) -> bool {
         self.layout.window_ids().next().is_none() && self.floating.is_empty()
     }

crates/ferese-core/src/workspace_policy.rs

@@ -14,6 +14,7 @@ pub struct WorkspaceView {
 }
 
 impl OutputWorkspaceMap {
+    #[must_use]
     pub fn workspace_views(&self, workspaces: &WorkspaceSet) -> Vec<WorkspaceView> {
         self.workspace_views_iter(workspaces).collect()
     }
@@ -47,6 +48,7 @@ impl OutputWorkspaceMap {
             })
     }
 
+    #[must_use]
     pub fn ordered_workspace_ids<'a>(
         &'a self,
         workspaces: &'a WorkspaceSet,
@@ -56,6 +58,7 @@ impl OutputWorkspaceMap {
             .filter(|id| workspaces.workspace(*id).is_some())
     }
 
+    #[must_use]
     pub fn ordered_workspaces(
         &self,
         workspaces: &WorkspaceSet,
@@ -66,6 +69,7 @@ impl OutputWorkspaceMap {
 
     /// Out-of-range numeric selection resolves to the trailing spare. Looking
     /// up a gesture target never creates workspaces or changes history.
+    #[must_use]
     pub fn workspace_at(
         &self,
         workspaces: &WorkspaceSet,