refactor(wm): use saturating_sub for idx-1 updates

This commit ensures that we use the saturating_sub function uniformly
when decrementing usize values by 1.

komorebi/src/container.rs

@@ -104,11 +104,7 @@ impl Container {
 
     pub fn remove_window_by_idx(&mut self, idx: usize) -> Option<Window> {
         let window = self.windows_mut().remove(idx);
-
-        if idx != 0 {
-            self.focus_window(idx - 1);
-        };
-
+        self.focus_window(idx.saturating_sub(1));
         window
     }
 
@@ -119,7 +115,7 @@ impl Container {
 
     pub fn add_window(&mut self, window: Window) {
         self.windows_mut().push_back(window);
-        self.focus_window(self.windows().len() - 1);
+        self.focus_window(self.windows().len().saturating_sub(1));
     }
 
     #[tracing::instrument(skip(self))]

komorebi/src/monitor.rs

@@ -127,7 +127,7 @@ impl Monitor {
         if idx == 0 {
             self.workspaces_mut().push_back(Workspace::default());
         } else {
-            self.focus_workspace(idx - 1).ok()?;
+            self.focus_workspace(idx.saturating_sub(1)).ok()?;
         };
 
         None

komorebi/src/window_manager.rs

@@ -1146,7 +1146,7 @@ impl WindowManager {
                 .ok_or_else(|| anyhow!("there is no monitor"))?;
 
             target_monitor.workspaces_mut().push_back(workspace);
-            target_monitor.focus_workspace(target_monitor.workspaces().len() - 1)?;
+            target_monitor.focus_workspace(target_monitor.workspaces().len().saturating_sub(1))?;
             target_monitor.load_focused_workspace(mouse_follows_focus)?;
         }
 
@@ -1281,10 +1281,9 @@ impl WindowManager {
                         let origin_workspace =
                             self.focused_workspace_for_monitor_idx_mut(origin_monitor_idx)?;
 
-                        if origin_workspace.focused_container_idx() != 0 {
-                            origin_workspace
-                                .focus_container(origin_workspace.focused_container_idx() - 1);
-                        }
+                        origin_workspace.focus_container(
+                            origin_workspace.focused_container_idx().saturating_sub(1),
+                        );
                     }
                 }
 
@@ -1449,10 +1448,10 @@ impl WindowManager {
             }
         }
 
-        workspace.focus_container(workspace.containers().len() - 1);
+        workspace.focus_container(workspace.containers().len().saturating_sub(1));
         while workspace.focused_container_idx() > 0 {
             workspace.move_window_to_container(0)?;
-            workspace.focus_container(workspace.containers().len() - 1);
+            workspace.focus_container(workspace.containers().len().saturating_sub(1));
         }
 
         if let Some(hwnd) = focused_hwnd {
@@ -1527,7 +1526,7 @@ impl WindowManager {
                     Layout::Default(DefaultLayout::Grid)
                         | Layout::Default(DefaultLayout::UltrawideVerticalStack)
                 ) {
-                new_idx - 1
+                new_idx.saturating_sub(1)
             } else {
                 new_idx
             };

komorebi/src/workspace.rs

@@ -802,7 +802,7 @@ impl Workspace {
             self.resize_dimensions_mut().remove(focused_idx);
 
             if focused_idx < target_container_idx {
-                target_container_idx - 1
+                target_container_idx.saturating_sub(1)
             } else {
                 target_container_idx
             }
@@ -924,8 +924,8 @@ impl Workspace {
                 self.containers_mut().remove(focused_idx);
                 self.resize_dimensions_mut().remove(focused_idx);
 
-                if focused_idx == self.containers().len() && focused_idx != 0 {
-                    self.focus_container(focused_idx - 1);
+                if focused_idx == self.containers().len() {
+                    self.focus_container(focused_idx.saturating_sub(1));
                 }
             } else {
                 container.load_focused_window();
@@ -1333,7 +1333,8 @@ impl Workspace {
             .ok_or_else(|| anyhow!("there is no monocle container"))?;
 
         let window = *window;
-        if !self.containers().is_empty() && restore_idx > self.containers().len() - 1 {
+        if !self.containers().is_empty() && restore_idx > self.containers().len().saturating_sub(1)
+        {
             self.containers_mut()
                 .resize(restore_idx, Container::default());
         }
@@ -1422,13 +1423,10 @@ impl Workspace {
 
     pub fn focus_previous_container(&mut self) {
         let focused_idx = self.focused_container_idx();
-
-        if focused_idx != 0 {
-            self.focus_container(focused_idx - 1);
-        }
+        self.focus_container(focused_idx.saturating_sub(1));
     }
 
     fn focus_last_container(&mut self) {
-        self.focus_container(self.containers().len() - 1);
+        self.focus_container(self.containers().len().saturating_sub(1));
     }
 }