Preserve passive canvas geometry while contextual help is open

crates/oa-desktop/src/app.rs

@@ -1383,6 +1383,16 @@ impl App {
                     | Message::SourceSymbolsReady(_)
                     | Message::SourceRenameReady(_)
                     | Message::DiagramUsagesReady(_)
+                    | Message::ScenarioCanvas(
+                        behavior::scenario::CanvasEvent::Scrolled(..)
+                            | behavior::scenario::CanvasEvent::Restored(..)
+                            | behavior::scenario::CanvasEvent::Viewport(..)
+                    )
+                    | Message::TopologyCanvas(
+                        behavior::topology::CanvasEvent::Scrolled(..)
+                            | behavior::topology::CanvasEvent::Viewport(..)
+                    )
+                    | Message::StateDiagram(behavior::state_edit::Event::Viewport(..))
             )
         {
             return Task::none();

crates/oa-desktop/src/app/context_help_tests.rs

@@ -272,3 +272,77 @@ fn context_help_rejects_a_reference_picker_open_queued_from_the_inspector() {
         before
     );
 }
+
+#[test]
+fn context_help_accepts_live_process_viewport_and_rejects_stale_measurements() {
+    use crate::behavior::topology::CanvasEvent;
+    let mut project = Project::empty();
+    let owner = project
+        .add_element(Kind::Process, Layer::Oa, "Response process", None)
+        .unwrap();
+    let mut app = App::with_project(project);
+    send(&mut app, Message::Select(owner));
+    send(&mut app, Message::Page(Page::Behavior));
+    let context = app.topology_context().unwrap();
+    send(
+        &mut app,
+        Message::TopologyCanvas(CanvasEvent::Viewport(context, iced::Size::new(640., 480.))),
+    );
+    let initial = app.behavior.topology.camera_boundary();
+    let before = app.document.snapshot();
+    send(&mut app, Message::Help);
+    assert!(app.context_help);
+    assert_eq!(app.guide.topic, Topic::Chains);
+
+    let resized = iced::Size::new(420., 330.);
+    let context = app.topology_context().unwrap();
+    send(
+        &mut app,
+        Message::TopologyCanvas(CanvasEvent::Viewport(context, resized)),
+    );
+    let measured = app.behavior.topology.camera_boundary();
+    assert!(
+        measured != initial,
+        "Help must admit passive viewport measurements"
+    );
+    assert!(app.context_help);
+    let epoch = app.canvas_epoch;
+    for field in 0..3 {
+        let mut stale = app.topology_context().unwrap();
+        match field {
+            0 => stale.document = Id::new_v4(),
+            1 => stale.owner = Id::new_v4(),
+            _ => stale.revision += 1,
+        }
+        send(
+            &mut app,
+            Message::TopologyCanvas(CanvasEvent::Viewport(stale, iced::Size::new(999., 777.))),
+        );
+        assert!(app.behavior.topology.camera_boundary() == measured);
+        assert_eq!(app.canvas_epoch, epoch);
+    }
+
+    send(&mut app, Message::CloseContextHelp);
+    assert!(!app.context_help);
+    assert!(app.behavior.topology.camera_boundary() == measured);
+    let context = app.topology_context().unwrap();
+    let epoch = app.canvas_epoch;
+    send(
+        &mut app,
+        Message::TopologyCanvas(CanvasEvent::Viewport(context, resized)),
+    );
+    assert_eq!(
+        app.canvas_epoch, epoch,
+        "The size observed behind Help is already current"
+    );
+    let context = app.topology_context().unwrap();
+    send(
+        &mut app,
+        Message::TopologyCanvas(CanvasEvent::Viewport(context, iced::Size::new(700., 500.))),
+    );
+    assert!(app.behavior.topology.camera_boundary() != measured);
+    assert_eq!(app.page, Page::Behavior);
+    assert_eq!(app.selected, owner);
+    assert!(Arc::ptr_eq(&before, &app.document.snapshot()));
+    assert!(!app.document.can_undo());
+}