feat(wm): add active window border

This commit adds an optional active window border with a user-defined
colour. This is achieved by spawning a dedicated "border window" and
constantly placing it behind the focused window, or hiding it whenever
necessary.

Some constraints to note:

- The border will only be applied to windows managed by komorebi
- This means that if you temporarily float a window, it will lose the
  active window border
- There are some issues where parts of the border will be broken by
  applications like Zoom, even if Zoom is behind the currently focused
  window
- You probably want to turn off window shadows globally in Advanced
  System Settings -> Performance for the borders to have a consistent
  colour all the way around the window
- There is some inevitable jank due to trying to reposition both the
  focused window and the "border window" behind it simultaneously
- There are no borders for unfocused windows

resolve #182

komorebic/src/main.rs

@@ -393,6 +393,22 @@ struct FocusFollowsMouse {
     boolean_state: BooleanState,
 }
 
+#[derive(Parser, AhkFunction)]
+struct ActiveWindowBorder {
+    #[clap(arg_enum)]
+    boolean_state: BooleanState,
+}
+
+#[derive(Parser, AhkFunction)]
+struct ActiveWindowBorderColour {
+    /// Red
+    r: u32,
+    /// Green
+    g: u32,
+    /// Blue
+    b: u32,
+}
+
 #[derive(Parser, AhkFunction)]
 struct Start {
     /// Allow the use of komorebi's custom focus-follows-mouse implementation
@@ -665,6 +681,12 @@ enum SubCommand {
     #[clap(arg_required_else_help = true)]
     #[clap(alias = "identify-border-overflow")]
     IdentifyBorderOverflowApplication(IdentifyBorderOverflowApplication),
+    /// Enable or disable the active window border
+    #[clap(arg_required_else_help = true)]
+    ActiveWindowBorder(ActiveWindowBorder),
+    /// Set the colour for the active window border
+    #[clap(arg_required_else_help = true)]
+    ActiveWindowBorderColour(ActiveWindowBorderColour),
     /// Enable or disable focus follows mouse for the operating system
     #[clap(arg_required_else_help = true)]
     FocusFollowsMouse(FocusFollowsMouse),
@@ -1182,6 +1204,14 @@ fn main() -> Result<()> {
         SubCommand::MouseFollowsFocus(arg) => {
             send_message(&SocketMessage::MouseFollowsFocus(arg.boolean_state.into()).as_bytes()?)?;
         }
+        SubCommand::ActiveWindowBorder(arg) => {
+            send_message(&SocketMessage::ActiveWindowBorder(arg.boolean_state.into()).as_bytes()?)?;
+        }
+        SubCommand::ActiveWindowBorderColour(arg) => {
+            send_message(
+                &SocketMessage::ActiveWindowBorderColour(arg.r, arg.g, arg.b).as_bytes()?,
+            )?;
+        }
         SubCommand::ResizeDelta(arg) => {
             send_message(&SocketMessage::ResizeDelta(arg.pixels).as_bytes()?)?;
         }