ui: timeline view stops at the comp end; a ruler scrub past the edge scrolls with the CTI

Co-Authored-By: Claude <noreply@anthropic.com>

(cherry picked from commit 562bfa51bd6ee86d1f8f5558b1ad466c7e4b4517)

(cherry picked from commit 0779d6944ede8afdff6ab49ea5d2caad19dfbfa3)
(cherry picked from commit 38e224f5c5037b7c79a283ab058582a3ad200339)

(cherry picked from commit 5e7b68be23ace400d92672ebf41c59124d29b101)

crates/ui-egui/src/panels/timeline.rs

@@ -1305,6 +1305,11 @@ pub fn show(app: &mut EffectcraftApp, ui: &mut egui::Ui, rect: Rect) {
         let span = ((graph_x1 - graph_x0 - 6.0) as f64 / pps).max(0.0);
         app.ui.timeline.start = page_to_cti(app.ui.timeline.start, span, comp.duration.seconds(), app.session.time().seconds());
     }
+    // As in After Effects, the ruler never scrolls past the comp's end: zoomed in, the last
+    // visible time is at most the comp duration.
+    let visible_secs = ((graph_x1 - graph_x0 - 6.0).max(1.0) as f64 / pps.max(1e-6)).max(0.0);
+    let max_start = (comp.duration.seconds() - visible_secs).max(0.0);
+    app.ui.timeline.start = app.ui.timeline.start.clamp(0.0, max_start);
     let tm = TMap { x0: graph_x0 + 6.0, start: app.ui.timeline.start, pps };
     ctx.data_mut(|d| d.insert_temp(tl_map_id(), (tm.x0, tm.start, tm.pps)));
     let top = rect.min.y;
@@ -1591,6 +1596,17 @@ pub fn show(app: &mut EffectcraftApp, ui: &mut egui::Ui, rect: Rect) {
         let tt = Tick::from_seconds_f64(secs);
         app.session.set_time(tt);
         app.stop();
+        // Dragged past either edge of the ruler (over the layer outline, say), the view scrolls so
+        // the current time indicator stays in sight (After Effects).
+        if app.ui.timeline.pps.is_some() {
+            let now = app.session.time().seconds();
+            let span = tm.t(bin.min.x) - tm.start;
+            if now < tm.start {
+                app.ui.timeline.start = now.max(0.0);
+            } else if now > tm.start + span {
+                app.ui.timeline.start = (now - span).max(0.0);
+            }
+        }
         // Ctrl/Cmd-drag scrubs the audio too (After Effects).
         if rresp.dragged()
             && ui.input(|i| i.modifiers.command)

crates/ui-egui/tests/ui_time_zoom_controls.rs

@@ -169,3 +169,29 @@ fn azerty_physical_zoom_keys_zoom_the_graph() {
     let (_, span2) = view(&h);
     assert!(span2 > span1 * 1.2, "Physical+Minus zooms the graph out: {span1} -> {span2}");
 }
+
+#[test]
+fn zoomed_in_the_ruler_stops_at_the_comp_end_and_a_scrub_past_the_edge_scrolls() {
+    let mut h = harness(false);
+    for _ in 0..4 {
+        send(&mut h, "ui.key", json!({"key": "="}));
+    }
+    // Scrolled as far right as it goes: the view ends at the comp's end, not past it (AE).
+    h.state_mut().ui.timeline.start = 9.9;
+    h.run_steps(3);
+    let (start, span) = view(&h);
+    assert!(span < 9.0, "zoomed in: {span}");
+    assert!((start + span - 10.0).abs() < 0.05, "the view ends at 10 s: {start} + {span}");
+    // A click at the ruler's right end puts the CTI there.
+    let ruler = h.state().auto.find("timeline.ruler").unwrap().rect;
+    let y = ruler[1] + ruler[3] - 4.0;
+    send(&mut h, "ui.click", json!({"x": ruler[0] + ruler[2] - 26.0, "y": y}));
+    let t = h.state().session.time().seconds();
+    assert!(t > start + span * 0.9, "the CTI jumps to the click near the end: {t}");
+    // Dragged from the ruler out over the layer outline, the view scrolls with the CTI.
+    send(&mut h, "ui.drag", json!({"from": {"x": ruler[0] + 40.0, "y": y}, "to": {"x": ruler[0] - 200.0, "y": y}, "steps": 20}));
+    let (start2, span2) = view(&h);
+    let t2 = h.state().session.time().seconds();
+    assert!(t2 < start, "the CTI moved left of the old view: {t2} vs {start}");
+    assert!(t2 >= start2 - 1e-6 && t2 <= start2 + span2, "the CTI stays in view: {t2} in {start2}+{span2}");
+}