Part of #4326: a lost mouse-up after the pointer moved does not click at the press

The released buttons go after the frame's last pointer movement, at its
position. Before, they went first, at the press position, so a press that
moved past the click distance in the same frame ended as a click on the
widget under the press.

crates/ui-egui/src/app/input.rs

@@ -151,9 +151,19 @@ impl VectorcraftApp {
             .collect();
             (down, p.latest_pos().or_else(|| p.interact_pos()).or_else(|| p.press_origin()), i.modifiers)
         });
+        // The releases go after this frame's last pointer movement, at its position, so a pointer
+        // that moved away from the press does not end it with a click at the press position.
+        let moved = raw.events.iter().enumerate().rev().find_map(|(i, e)| match e {
+            egui::Event::PointerMoved(p) => Some((i + 1, *p)),
+            _ => None,
+        });
+        let (at, pos) = match moved {
+            Some((at, p)) => (at, Some(p)),
+            None => (0, pos),
+        };
         let Some(pos) = pos else { return };
         let releases = down.into_iter().map(|button| egui::Event::PointerButton { pos, button, pressed: false, modifiers });
-        raw.events.splice(0..0, releases);
+        raw.events.splice(at..at, releases);
     }
 
     /// Inject synthetic events (one press/release step, wheel turn or short key sequence per host

crates/ui-egui/src/panel_docking/tests.rs

@@ -439,6 +439,15 @@ fn a_column_resize_continues_while_the_system_reports_the_button_down() {
     assert!(h.ctx.input(|i| i.pointer.primary_down()));
 }
 
+#[test]
+fn a_lost_release_after_the_pointer_moved_away_is_not_a_click() {
+    let mut h = Harness::new();
+    h.frame(vec![Event::PointerMoved(pos2(800.0, 600.0)), button(pos2(800.0, 600.0), true)]);
+    h.frame_with_system_buttons(vec![Event::PointerMoved(pos2(1000.0, 600.0))], false);
+    assert!(!h.ctx.input(|i| i.pointer.any_down()));
+    assert!(!h.ctx.input(|i| i.pointer.any_click()), "the release at the press position made a click");
+}
+
 #[test]
 fn control_channel_drags_keep_their_button_between_steps() {
     let mut h = Harness::new();