feat: niri msg pick-window

Fixes YaLTeR#589.

niri-ipc/src/lib.rs

@@ -63,6 +63,8 @@ pub enum Request {
     FocusedOutput,
     /// Request information about the focused window.
     FocusedWindow,
+    /// Request picking a window and get its information.
+    PickWindow,
     /// Perform an action.
     Action(Action),
     /// Change output configuration temporarily.
@@ -129,6 +131,10 @@ pub enum Response {
     FocusedOutput(Option<Output>),
     /// Information about the focused window.
     FocusedWindow(Option<Window>),
+    /// Information about the picked window.
+    ///
+    /// `None` if the request was cancelled by the user.
+    PickedWindow(Option<Window>),
     /// Output configuration change result.
     OutputConfigChanged(OutputConfigChanged),
 }

src/cli.rs

@@ -72,6 +72,8 @@ pub enum Msg {
     FocusedOutput,
     /// Print information about the focused window.
     FocusedWindow,
+    /// Request picking a window.
+    PickWindow,
     /// Perform an action.
     Action {
         #[command(subcommand)]

src/input/mod.rs

@@ -361,6 +361,14 @@ impl State {
                     }
                 }
 
+                if let Some(tx) = this
+                    .niri
+                    .pick_window
+                    .take_if(move |_| raw == Some(Keysym::Escape))
+                {
+                    let _ = tx.send_blocking(None);
+                }
+
                 should_intercept_key(
                     &mut this.niri.suppressed_keys,
                     bindings,
@@ -1833,6 +1841,13 @@ impl State {
             self.niri.pointer_hidden = false;
             self.niri.tablet_cursor_location = None;
 
+            if let Some(mapped_id) = self.niri.window_under_cursor().map(|mapped| mapped.id()) {
+                if let Some(tx) = self.niri.pick_window.take() {
+                    let _ = tx.send_blocking(Some(mapped_id));
+                    return;
+                }
+            }
+
             if let Some(mapped) = self.niri.window_under_cursor() {
                 let window = mapped.window.clone();
 

src/ipc/client.rs

@@ -19,6 +19,7 @@ pub fn handle_msg(msg: Msg, json: bool) -> anyhow::Result<()> {
         Msg::Outputs => Request::Outputs,
         Msg::FocusedWindow => Request::FocusedWindow,
         Msg::FocusedOutput => Request::FocusedOutput,
+        Msg::PickWindow => Request::PickWindow,
         Msg::Action { action } => Request::Action(action.clone()),
         Msg::Output { output, action } => Request::Output {
             output: output.clone(),
@@ -252,6 +253,23 @@ pub fn handle_msg(msg: Msg, json: bool) -> anyhow::Result<()> {
                 println!("No output is focused.");
             }
         }
+        Msg::PickWindow => {
+            let Response::PickedWindow(window) = response else {
+                bail!("unexpected response: expected PickedWindow, got {response:?}");
+            };
+
+            if json {
+                let window = serde_json::to_string(&window).context("error formatting response")?;
+                println!("{window}");
+                return Ok(());
+            }
+
+            if let Some(window) = window {
+                print_window(&window);
+            } else {
+                println!("Picking window was cancelled.");
+            }
+        }
         Msg::Action { .. } => {
             let Response::Handled = response else {
                 bail!("unexpected response: expected Handled, got {response:?}");

src/ipc/server.rs

@@ -309,6 +309,19 @@ async fn process(ctx: &ClientCtx, request: Request) -> Reply {
             let window = windows.values().find(|win| win.is_focused).cloned();
             Response::FocusedWindow(window)
         }
+        Request::PickWindow => {
+            let (tx, rx) = async_channel::bounded(1);
+            ctx.event_loop.insert_idle(move |state| {
+                state.niri.pick_window = Some(tx);
+            });
+            let result = rx.recv().await;
+            let id = result.map_err(|_| String::from("error getting picked window info"))?;
+            let window = id.and_then(|id| {
+                let state = ctx.event_stream_state.borrow();
+                state.windows.windows.get(&id.get()).cloned()
+            });
+            Response::PickedWindow(window)
+        }
         Request::Action(action) => {
             let (tx, rx) = async_channel::bounded(1);
 

src/niri.rs

@@ -153,6 +153,7 @@ use crate::utils::{
     center, center_f64, get_monotonic_time, ipc_transform_to_smithay, logical_output,
     make_screenshot_path, output_matches_name, output_size, send_scale_transform, write_png_rgba8,
 };
+use crate::window::mapped::MappedId;
 use crate::window::{InitialConfigureState, Mapped, ResolvedWindowRules, Unmapped, WindowRef};
 
 const CLEAR_COLOR_LOCKED: [f32; 4] = [0.3, 0.1, 0.1, 1.];
@@ -332,6 +333,8 @@ pub struct Niri {
     pub hotkey_overlay: HotkeyOverlay,
     pub exit_confirm_dialog: Option<ExitConfirmDialog>,
 
+    pub pick_window: Option<async_channel::Sender<Option<MappedId>>>,
+
     pub debug_draw_opaque_regions: bool,
     pub debug_draw_damage: bool,
 
@@ -2075,6 +2078,8 @@ impl Niri {
             hotkey_overlay,
             exit_confirm_dialog,
 
+            pick_window: None,
+
             debug_draw_opaque_regions: false,
             debug_draw_damage: false,