Preserve background pan and retire legacy Scenario selection gestures

crates/oa-desktop/src/behavior/scenario/workspace.rs

@@ -198,7 +198,12 @@ pub fn view<'a>(app: &'a App, owner: Id, out: Column<'a, Message>) -> Element<'a
         container(text("No supported canvas geometry is available. Inspect the model or open its source to repair this view."))
             .id("scenario-viewport-unavailable").padding(16).width(Fill).height(Fill).style(style::card).into()
     };
-    let mut navigation = row![out.width(Fill)].spacing(6);
+    let selected_count = snapshot.as_ref().map_or(0, |s| s.targets().len());
+    let mut navigation = row![
+        out.width(Fill),
+        text(format!("{selected_count} selected")).size(12)
+    ]
+    .spacing(6);
     if state.can_back(p, context) {
         navigation =
             navigation.push(button(text("Back").size(12)).padding(6).on_press_maybe(
@@ -264,7 +269,9 @@ pub fn view<'a>(app: &'a App, owner: Id, out: Column<'a, Message>) -> Element<'a
     let entries = [
         (
             "S",
-            if matches!(context.representation, Representation::Saved { .. }) {
+            if selected_count > 1 {
+                "Shift-click to change selection; click a member to select only it"
+            } else if matches!(context.representation, Representation::Saved { .. }) {
                 "Select / move messages and lifelines"
             } else {
                 "Select / reorder occurrences"
@@ -345,7 +352,15 @@ pub fn view<'a>(app: &'a App, owner: Id, out: Column<'a, Message>) -> Element<'a
         }),
     );
     let mut details = column![
-        text(format!("Selected: {}", p.named(app.selected))).size(12),
+        text(if selected_count > 1 {
+            format!(
+                "{selected_count} selected; properties: {}",
+                p.named(app.selected)
+            )
+        } else {
+            format!("Selected: {}", p.named(app.selected))
+        })
+        .size(12),
         container(button(text("Properties").size(12)).on_press_maybe(
             (clean && properties_target(p, context, app.selected)).then_some(
                 Message::ScenarioCanvas(CanvasEvent::Properties(context, app.selected)),