Merge pull request #4770 from dotCooCoo/fix/backtick-mid-drag-preview

Canvas: pressing or releasing backquote mid-drag updates the live preview

crates/ui-egui/src/canvas/drag.rs

@@ -79,13 +79,14 @@ pub(super) fn tool_drag_moved(ui: &Ui, xf: &Xf, p: Pos2, pointer: &egui::Pointer
 }
 
 /// Whether the tool should get another drag event at a pointer held still because Shift, Alt,
-/// Cmd/Ctrl or Space went down or up (#4711): a scale switches to proportional or from the centre
-/// at once. Records `m` as the modifiers last seen; only once the press has dragged.
-pub(super) fn tool_drag_mods_changed(ui: &Ui, m: Mods) -> bool {
+/// Cmd/Ctrl, Space or Backtick went down or up (#4711): a scale switches to proportional or from the centre
+/// at once. Records `m` and the Backtick state as last seen; only once the press has dragged.
+pub(super) fn tool_drag_mods_changed(ui: &Ui, m: Mods, backquote: bool) -> bool {
     let id = egui::Id::unique("canvas-tool-drag-mods");
-    let (dragged, last) = ui.data(|d| (d.get_temp::<Point>(tool_drag_doc_id()).is_some(), d.get_temp::<Mods>(id)));
-    ui.data_mut(|d| d.insert_temp(id, m));
-    dragged && last.is_some_and(|l| l != m)
+    let held = (m, backquote);
+    let (dragged, last) = ui.data(|d| (d.get_temp::<Point>(tool_drag_doc_id()).is_some(), d.get_temp::<(Mods, bool)>(id)));
+    ui.data_mut(|d| d.insert_temp(id, held));
+    dragged && last.is_some_and(|l| l != held)
 }
 
 /// The pen pressure (0..1) of the press in progress: the force of this frame's pen or touch

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

@@ -379,27 +379,18 @@ fn drag_held(app: &mut VectorcraftApp, ui: &Ui, f: &Pointing, d: Drag, p: Pos2)
             // the last position only, so a costly drag preview runs once a frame.
             let moves = tool_frame_moves(ui, app);
             // A frame whose pointer ends where the last one did still moved in between.
-            let mods_changed = tool_drag_mods_changed(ui, mods(m, space));
+            let backquote = ui.input(|i| i.key_down(egui::Key::Backtick));
+            let mods_changed = tool_drag_mods_changed(ui, mods(m, space), backquote);
             if tool_drag_moved(ui, &xf, p, pointer) || mods_changed || !moves.is_empty() {
                 for (at, force) in moves {
                     let pressure = force.unwrap_or_else(|| pen_pressure(ui, app, false));
-                    dispatch(
-                        app,
-                        &PointerEvent {
-                            kind: PointerKind::Drag,
-                            pos: xf.to_doc(at),
-                            mods: mods(m, space),
-                            backquote: ui.input(|i| i.key_down(egui::Key::Backtick)),
-                            pressure,
-                        },
-                        view,
-                    );
+                    dispatch(app, &PointerEvent { kind: PointerKind::Drag, pos: xf.to_doc(at), mods: mods(m, space), backquote, pressure }, view);
                 }
                 let ev = PointerEvent {
                     kind: PointerKind::Drag,
                     pos: xf.to_doc(p),
                     mods: mods(m, space),
-                    backquote: ui.input(|i| i.key_down(egui::Key::Backtick)),
+                    backquote,
                     pressure: pen_pressure(ui, app, false),
                 };
                 dispatch(app, &ev, view);

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

@@ -6135,6 +6135,51 @@ fn a_modifier_changed_mid_scale_applies_with_the_pointer_held_still() {
     assert!(app.session.active().unwrap().interaction.is_none(), "committed");
 }
 
+/// Backtick switches a moved Selection drag's live preview while the pointer stays still.
+#[test]
+fn backtick_changed_mid_selection_drag_applies_with_the_pointer_held_still() {
+    use egui::Event;
+    let mut app = VectorcraftApp::new(Session::new(), Default::default());
+    app.run("file.new", json!({"width": 400, "height": 300})).unwrap();
+    let tile = app.run("shape.rectangle", json!({"x": 0, "y": 0, "width": 10, "height": 10})).unwrap()["id"].as_u64().unwrap();
+    app.run("object.pattern.make", json!({"ids": [tile], "name": "Dots", "width": 20, "height": 20})).unwrap();
+    app.run("object.pattern.done", json!({})).unwrap();
+    let id = app.run("shape.rectangle", json!({"x": 100, "y": 100, "width": 50, "height": 50})).unwrap()["id"].as_u64().unwrap();
+    app.run("paint.setFill", json!({"ids": [id], "swatch": "Dots"})).unwrap();
+    app.run("select.set", json!({"ids": [id]})).unwrap();
+    app.select_tool("selection");
+    app.ui.task_bar = false;
+    app.ui.view.rulers = false;
+    app.ui.view.smart_guides = false;
+    app.ui.view.snap_to_point = false;
+    let ctx = egui::Context::default();
+    frame(&mut app, &ctx, vec![]);
+    let xf = Xf::new(app.canvas_rect.unwrap(), app.view().unwrap());
+    let from = xf.to_screen(Point::new(125.0, 125.0));
+    let to = xf.to_screen(Point::new(145.0, 125.0));
+    let button = |pos, pressed| Event::PointerButton { pos, button: egui::PointerButton::Primary, pressed, modifiers: Default::default() };
+    let key = |pressed| Event::Key { key: egui::Key::Backtick, physical_key: None, pressed, repeat: false, modifiers: Default::default() };
+    let node = |app: &VectorcraftApp| app.session.doc().unwrap().doc.node(vectorcraft_doc::NodeId(id)).unwrap().clone();
+    let pattern_x = |node: &vectorcraft_doc::Node| {
+        let vectorcraft_color::Paint::Pattern { xf, .. } = node.appearance.fill_paint() else { panic!("pattern fill expected") };
+        xf.as_coeffs()[4]
+    };
+    let before = node(&app);
+    frame(&mut app, &ctx, vec![Event::PointerMoved(from), button(from, true)]);
+    frame(&mut app, &ctx, vec![Event::PointerMoved(to)]);
+    let moved = node(&app);
+    assert!((moved.geometric_bounds().unwrap().x0 - before.geometric_bounds().unwrap().x0 - 20.0).abs() < 0.001);
+    frame(&mut app, &ctx, vec![key(true)]);
+    let pattern_only = node(&app);
+    assert_eq!(pattern_only.geometric_bounds(), before.geometric_bounds(), "Backtick restores geometry in the live preview");
+    assert!((pattern_x(&pattern_only) - pattern_x(&before) - 20.0).abs() < 0.001, "Backtick moves the pattern in the live preview");
+    frame(&mut app, &ctx, vec![key(false)]);
+    let ordinary = node(&app);
+    assert_eq!(ordinary.geometric_bounds(), moved.geometric_bounds(), "releasing Backtick restores the ordinary move in the live preview");
+    assert!((pattern_x(&ordinary) - pattern_x(&before)).abs() < 0.001, "the ordinary move restores the pattern matrix");
+    frame(&mut app, &ctx, vec![button(to, false)]);
+}
+
 /// #834 review: a press held still is not a drag. Before the press has dragged, the first held
 /// frame without a delta at the press's own position sends nothing, so a click stays a click;
 /// the first move after it does.