feat(ui): the status bar keeps the last pointer position off the map

crates/ui-egui/src/chrome.rs

@@ -305,9 +305,13 @@ pub fn status_bar(app: &mut RustGisApp, ui: &mut Ui) {
                 // Pointer coordinates.
                 let format = app.map.coord_format;
                 let earth = app.session.map().body().is_earth();
+                // Kept after the pointer leaves the map, so a click here still shows the position;
+                // dimmed then, to tell it from a live one.
+                let kept = app.map.kept_pointer_lonlat(app.session.map().instance_id(), app.session.opened);
+                let live = app.map.pointer_lonlat.is_some();
                 let resp = ui.add(
                     egui::Label::new(
-                        egui::RichText::new(format.readout(app.map.pointer_lonlat, earth)).monospace().size(11.5).color(t.text_dim),
+                        egui::RichText::new(format.readout(kept, earth)).monospace().size(11.5).color(if live { t.text_dim } else { t.text_disabled }),
                     )
                     .sense(Sense::click()),
                 );

crates/ui-egui/src/mapview.rs

@@ -302,6 +302,9 @@ pub struct MapView {
     /// A map or layout waiting for the user to confirm its deletion.
     pub deleting: Option<Deletion>,
     pub pointer_lonlat: Option<Coord>,
+    /// The last pointer position seen over a map, kept for the status bar readout after the
+    /// pointer leaves the map; with the map's instance and the session's `opened` it belongs to.
+    kept_lonlat: Option<(Coord, u64, u64)>,
     /// Where the map's context menu was opened: the pointer leaves the map for the menu.
     pub menu_lonlat: Option<Coord>,
     /// The text graphic the context menu was opened on (layer id, row), for Edit Text.
@@ -403,6 +406,7 @@ impl Default for MapView {
             popup_rev: 0,
             deleting: None,
             pointer_lonlat: None,
+            kept_lonlat: None,
             menu_lonlat: None,
             menu_text: None,
             coord_format: crate::CoordReadout::Decimal,
@@ -437,6 +441,18 @@ impl Default for MapView {
 }
 
 impl MapView {
+    /// The position the status bar shows: the last one over this map, kept while the pointer is
+    /// elsewhere. A position from another map or project no longer applies, so it is dropped.
+    pub fn kept_pointer_lonlat(&mut self, map_instance: u64, opened: u64) -> Option<Coord> {
+        match self.kept_lonlat {
+            Some((c, m, o)) if m == map_instance && o == opened => Some(c),
+            _ => {
+                self.kept_lonlat = None;
+                None
+            }
+        }
+    }
+
     /// Whether an exact frame is being composed off the UI thread, or the frame shown waits for
     /// tile pictures still to be drawn.
     pub fn drawing(&self) -> bool {
@@ -2257,6 +2273,9 @@ fn interact(app: &mut RustGisApp, ui: &mut Ui, resp: &egui::Response, rect: Rect
     let time = now(ui);
     let hover = resp.hover_pos();
     app.map.pointer_lonlat = hover.and_then(|p| screen_to_lonlat(app, rect, p));
+    if let Some(c) = app.map.pointer_lonlat.filter(|c| c.is_finite()) {
+        app.map.kept_lonlat = Some((c, app.session.map().instance_id(), app.session.opened));
+    }
     let tool = app.session.tool;
     cancel_changed_selection(app, rect);
 

crates/ui-egui/tests/coordinate_readout.rs

@@ -136,3 +136,79 @@ fn the_status_bar_reads_the_pointer_in_the_chosen_format_and_a_click_switches()
     hover_map(&mut h);
     h.get_by_label(&rustgis_engine::geom::format_lonlat(h.state().map.pointer_lonlat.unwrap()));
 }
+
+/// Moves the mouse onto the status bar, off the map, for a few frames.
+fn hover_status_bar(h: &mut egui_kittest::Harness<'_, RustGisApp>) {
+    for _ in 0..3 {
+        h.input_mut().events.push(egui::Event::PointerMoved(egui::pos2(800.0, 892.0)));
+        h.step();
+    }
+}
+
+fn readout_at_center(h: &mut egui_kittest::Harness<'_, RustGisApp>) -> String {
+    h.state_mut().run("map.goToXY", json!({"lon": 44.4, "lat": 33.3, "scale": 10000})).unwrap();
+    hover_map(h);
+    rustgis_engine::geom::format_lonlat(h.state().map.pointer_lonlat.expect("the pointer is over the map"))
+}
+
+#[test]
+fn the_readout_is_a_dash_until_the_pointer_has_been_over_the_map() {
+    let mut h = harness(RustGisApp::with_sample());
+    h.step();
+    h.get_by_label("—");
+    hover_status_bar(&mut h);
+    h.get_by_label("—");
+    assert!(h.state().map.pointer_lonlat.is_none());
+}
+
+#[test]
+fn the_position_stays_when_the_pointer_leaves_the_map_and_a_click_switches_format() {
+    let mut h = harness(RustGisApp::with_sample());
+    let decimal = readout_at_center(&mut h);
+    hover_status_bar(&mut h);
+    assert!(h.state().map.pointer_lonlat.is_none());
+    h.get_by_label(&decimal);
+    // The pointer in the window's corner, or gone altogether, keeps it too.
+    h.input_mut().events.push(egui::Event::PointerGone);
+    h.step();
+    h.get_by_label(&decimal);
+    // A click on the readout shows the same position in the next format.
+    h.get_by_label(&decimal).click();
+    h.step();
+    h.step();
+    assert_eq!(h.state().map.coord_format, CoordReadout::Dms);
+    let at = h.state().map.pointer_lonlat;
+    assert!(at.is_none());
+    h.get_by_label_contains("44°");
+    // The pointer back over the map follows it again.
+    hover_map(&mut h);
+    assert!(h.state().map.pointer_lonlat.is_some());
+}
+
+#[test]
+fn the_position_is_dropped_on_another_map_or_project() {
+    let mut h = harness(RustGisApp::with_sample());
+    let decimal = readout_at_center(&mut h);
+    hover_status_bar(&mut h);
+    h.get_by_label(&decimal);
+    // Another map becoming the active one.
+    h.state_mut().run("map.new", json!({"name": "Second Map"})).unwrap();
+    h.step();
+    h.step();
+    assert!(h.query_by_label(&decimal).is_none());
+    h.get_by_label("—");
+    // Back on the first map it is not remembered from before.
+    h.state_mut().run("map.activate", json!({"name": "World Atlas"})).ok();
+    h.step();
+    h.step();
+    h.get_by_label("—");
+    // A new position, then another project replacing this one.
+    let decimal = readout_at_center(&mut h);
+    hover_status_bar(&mut h);
+    h.get_by_label(&decimal);
+    h.state_mut().run("project.new", json!({})).unwrap();
+    h.step();
+    h.step();
+    assert!(h.query_by_label(&decimal).is_none());
+    h.get_by_label("—");
+}

docs/user-guide/maps.md

@@ -138,8 +138,11 @@ and **View In Google Earth** open the place in your browser at about the same zo
 
 ### Coordinate readouts
 
-The status bar shows the pointer's coordinates. Click them to step through four formats; the
-choice is remembered and also sets the right-click menu's first row. The same place in each:
+The status bar shows the pointer's coordinates while it is over the map, and keeps the last
+position (dimmed) when it leaves, so you can move to the status bar and click it. It reads `—`
+until the pointer has been over the map, and again after you switch to another map or open another
+project. Click the coordinates to step through four formats; the choice is remembered and also
+sets the right-click menu's first row. The same place in each:
 
 | Format | Example | |
 | --- | --- | --- |