feat: space switches region mode to window mode

src/main.rs

@@ -172,10 +172,17 @@ fn capture(mode: Mode, common: Common) -> Result<()> {
         }
         Mode::Region => {
             let frames = wl.capture(&outputs, cursor)?;
-            let (i, r) = region::select(&mut wl, &outputs, &frames)?;
+            match region::select(&mut wl, &outputs, &frames)? {
+                region::Choice::Region(i, r) => {
                     let source = frames[i].output.name.clone();
                     (vec![(frames[i].to_rgba(r), None)], 0, source)
                 }
+                region::Choice::Window => {
+                    drop(frames);
+                    window_shot(&outputs, cursor)?
+                }
+            }
+        }
         Mode::Window => window_shot(&outputs, cursor)?,
     };
     drop(wl);

src/region.rs

@@ -30,8 +30,14 @@ use crate::wayland::{Output, State, Wayland};
 
 pub const NAMESPACE: &str = "valw-overlay";
 
-/// What the user picked: an output index and a rectangle in its frame.
-pub type Picked = (usize, PixelRect);
+/// What the user chose in the overlay.
+#[derive(Debug, PartialEq)]
+pub enum Choice {
+    /// A rectangle in the frame of output `.0`.
+    Region(usize, PixelRect),
+    /// Space before dragging: capture a window instead.
+    Window,
+}
 
 /// One full-screen layer surface per output, showing the frozen frame.
 pub struct Overlay {
@@ -39,7 +45,7 @@ pub struct Overlay {
     selection: Selection,
     /// Output where the current drag started; the capture is clipped to it.
     anchor: Option<usize>,
-    outcome: Option<Option<Picked>>,
+    outcome: Option<Option<Choice>>,
 }
 
 struct Surface {
@@ -59,7 +65,8 @@ struct Surface {
 
 /// Shows the overlay on every output and waits for a selection.
 /// Returns `Cancelled` if the user presses Esc or right-clicks.
-pub fn select(wl: &mut Wayland, outputs: &[Output], frames: &[Frame]) -> Result<Picked> {
+/// Space before dragging returns `Choice::Window`.
+pub fn select(wl: &mut Wayland, outputs: &[Output], frames: &[Frame]) -> Result<Choice> {
     let qh = wl.queue.handle();
     let s = &wl.state;
     let layer_shell = s
@@ -162,6 +169,13 @@ impl Overlay {
         self.outcome.get_or_insert(None);
     }
 
+    pub fn switch_to_window(&mut self) {
+        if self.selection.allows_window_switch() {
+            tracing::info!("switching to window mode");
+            self.outcome.get_or_insert(Some(Choice::Window));
+        }
+    }
+
     fn index_of(&self, surface: &WlSurface) -> Option<usize> {
         self.surfaces
             .iter()
@@ -266,7 +280,7 @@ impl Overlay {
                                 "selected {rect:?} on {} (logical {start:?} to {end:?})",
                                 s.geom.name
                             );
-                            self.outcome = Some(Some((a, rect)));
+                            self.outcome = Some(Some(Choice::Region(a, rect)));
                         }
                         // A click, not a drag: clear it and keep waiting.
                         None => self.redraw(a, qh),

src/selection.rs

@@ -38,6 +38,11 @@ impl Selection {
             Selection::Idle => None,
         }
     }
+
+    /// Space switches to window mode only before a drag starts.
+    pub fn allows_window_switch(&self) -> bool {
+        *self == Selection::Idle
+    }
 }
 
 /// The part of the drag from `a` to `b` that falls on `out`, in the physical
@@ -77,6 +82,16 @@ pub fn resolve(
 mod tests {
     use super::*;
 
+    #[test]
+    fn window_switch_only_before_a_drag() {
+        let mut s = Selection::default();
+        assert!(s.allows_window_switch());
+        s.press(Point { x: 1.0, y: 1.0 });
+        assert!(!s.allows_window_switch(), "Space during a drag is reserved");
+        s.release(Point { x: 5.0, y: 5.0 });
+        assert!(s.allows_window_switch());
+    }
+
     fn out(name: &str, x: i32, y: i32, width: i32, height: i32) -> OutputGeom {
         OutputGeom {
             name: name.into(),

src/wayland.rs

@@ -449,10 +449,13 @@ impl KeyboardHandler for State {
         _: u32,
         event: KeyEvent,
     ) {
-        if event.keysym == Keysym::Escape
-            && let Some(overlay) = &mut self.overlay
-        {
-            overlay.cancel();
+        let Some(overlay) = &mut self.overlay else {
+            return;
+        };
+        match event.keysym {
+            Keysym::Escape => overlay.cancel(),
+            Keysym::space => overlay.switch_to_window(),
+            _ => {}
         }
     }