Implement `niri msg pick-window`

* feat: `niri msg pick-window`

* fixes

---------

Co-authored-by: Ivan Molodetskikh <yalterz@gmail.com>

2 files changed, 52 insertions, 0 deletions

diff --git a/src/ipc/client.rs b/src/ipc/client.rs
index 8682d8d3..66cdaf7d 100644
--- a/src/ipc/client.rs
+++ b/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!("No window selected.");
+            }
+        }
         Msg::Action { .. } => {
             let Response::Handled = response else {
                 bail!("unexpected response: expected Handled, got {response:?}");
diff --git a/src/ipc/server.rs b/src/ipc/server.rs
index 6706928a..c8f8edcf 100644
--- a/src/ipc/server.rs
+++ b/src/ipc/server.rs
@@ -18,12 +18,17 @@ use niri_config::OutputName;
 use niri_ipc::state::{EventStreamState, EventStreamStatePart as _};
 use niri_ipc::{Event, KeyboardLayouts, OutputConfigChanged, Reply, Request, Response, Workspace};
 use smithay::desktop::layer_map_for_output;
+use smithay::input::pointer::{
+    CursorIcon, CursorImageStatus, Focus, GrabStartData as PointerGrabStartData,
+};
 use smithay::reexports::calloop::generic::Generic;
 use smithay::reexports::calloop::{Interest, LoopHandle, Mode, PostAction};
 use smithay::reexports::rustix::fs::unlink;
+use smithay::utils::SERIAL_COUNTER;
 use smithay::wayland::shell::wlr_layer::{KeyboardInteractivity, Layer};
 
 use crate::backend::IpcOutputMap;
+use crate::input::pick_window_grab::PickWindowGrab;
 use crate::layout::workspace::WorkspaceId;
 use crate::niri::State;
 use crate::utils::{version, with_toplevel_role};
@@ -322,6 +327,35 @@ 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| {
+                let pointer = state.niri.seat.get_pointer().unwrap();
+                let start_data = PointerGrabStartData {
+                    focus: None,
+                    button: 0,
+                    location: pointer.current_location(),
+                };
+                let grab = PickWindowGrab::new(start_data);
+                // The `WindowPickGrab` ungrab handler will cancel the previous ongoing pick, if
+                // any.
+                pointer.set_grab(state, grab, SERIAL_COUNTER.next_serial(), Focus::Clear);
+                state.niri.pick_window = Some(tx);
+                state
+                    .niri
+                    .cursor_manager
+                    .set_cursor_image(CursorImageStatus::Named(CursorIcon::Crosshair));
+                // Redraw to update the cursor.
+                state.niri.queue_redraw_all();
+            });
+            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);