tree: support toggling floating with double clicks

src/utils/double_click_state.rs

@@ -0,0 +1,35 @@
+use crate::state::State;
+
+#[derive(Default)]
+pub struct DoubleClickState {
+    last_click: Option<(u64, i32, i32)>,
+}
+
+impl DoubleClickState {
+    pub fn click(&mut self, state: &State, time_usec: u64, x: i32, y: i32) -> bool {
+        let res = self.click_(state, time_usec, x, y);
+        if !res {
+            self.last_click = Some((time_usec, x, y));
+        }
+        res
+    }
+
+    fn click_(&mut self, state: &State, time_usec: u64, x: i32, y: i32) -> bool {
+        let Some((last_usec, last_x, last_y)) = self.last_click.take() else {
+            return false;
+        };
+        if time_usec.wrapping_sub(last_usec) > state.double_click_interval_usec.get() {
+            return false;
+        }
+        let max_dist = state.double_click_distance.get();
+        if max_dist < 0 {
+            return false;
+        }
+        let dist_x = last_x - x;
+        let dist_y = last_y - y;
+        if dist_x * dist_x + dist_y * dist_y > max_dist * max_dist {
+            return false;
+        }
+        true
+    }
+}