ui: the handed-over drop ignores a window that only saw the file hover

Co-Authored-By: DeepSeek V4.1 Flash <noreply@deepseek.com>

crates/ui-egui/src/dock_ui.rs

@@ -530,9 +530,7 @@ impl EffectcraftApp {
         let typing = ctx.egui_wants_keyboard_input();
         let events = events.into_iter().filter(|event| !typing && !matches!(event, egui::Event::Text(_) | egui::Event::Ime(_)));
         self.forwarded.events.extend(events);
-        // A floating window's drop names the panel under its pointer, which the main window's
-        // pointer can never hit (#2661).
-        if files.iter().any(|window| matches!(window.panel, PanelKind::Timeline)) {
+        if handed_over_to_the_timeline(files.iter().map(|window| (window.panel, !window.dropped.is_empty()))) {
             self.forwarded.dropped_on_timeline = true;
         }
         self.forwarded.files.extend(files.into_iter().flat_map(|window| window.dropped));
@@ -867,3 +865,33 @@ impl DockContent<PanelKind> for EffectContent<'_> {
         }
     }
 }
+
+/// Whether a handed-over *drop* named the Timeline. A floating window reports its hovered files
+/// too, so a drag that only passes over the Timeline window must not count: its flag would survive
+/// and send the next drop somewhere else. The panel comes from the window, which the main window's
+/// pointer can never reach (#2661).
+fn handed_over_to_the_timeline(drops: impl Iterator<Item = (PanelKind, bool)>) -> bool {
+    drops.into_iter().any(|(panel, has_files)| has_files && matches!(panel, PanelKind::Timeline))
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    /// A drop handed over by a floating window says which panel it landed on; only the Timeline
+    /// turns it into a layer instead of a project item. A window that only saw the file hover over
+    /// it carries no files and must not count, or its flag would outlive the drag (#2661).
+    #[test]
+    fn only_a_timeline_drop_is_handed_over_to_the_timeline() {
+        let cases = [
+            (vec![(PanelKind::Timeline, true)], true),
+            (vec![(PanelKind::Project, true)], false),
+            (vec![(PanelKind::Timeline, false)], false),
+            (vec![(PanelKind::Project, true), (PanelKind::Timeline, true)], true),
+            (vec![], false),
+        ];
+        for (windows, want) in cases {
+            assert_eq!(handed_over_to_the_timeline(windows.into_iter()), want, "{want}");
+        }
+    }
+}

crates/ui-egui/src/prefs_live.rs

@@ -63,8 +63,8 @@ pub fn dropped_files(app: &mut EffectcraftApp, ui: &egui::Ui, bounds: Rect) {
         errors.push(crate::i18n::tr_args("Skipped {} dropped file(s) without a local path. Use File ▸ Import ▸ File…", &[&skipped]));
     }
 
-    // Taken once per drop, before any early return, so a project-only drop cannot leave it set
-    // for the next one (#2661).
+    // Taken once per drop frame, so a handed-over flag cannot survive into a later, unrelated
+    // drop (#2661).
     let handed_by_a_floating_window = std::mem::take(&mut app.forwarded.dropped_on_timeline);
 
     let (proj, rest): (Vec<String>, Vec<String>) = paths.into_iter().partition(|p| {
@@ -94,12 +94,12 @@ pub fn dropped_files(app: &mut EffectcraftApp, ui: &egui::Ui, bounds: Rect) {
         // on the viewer (#2588); the import decides the layer's position.
         let over_timeline = handed_by_a_floating_window
             || ctx.input(|i| i.pointer.hover_pos()).is_some_and(|p| {
-            app.auto
-                .elements
-                .iter()
-                .find(|e| e.id == "panel.Timeline")
-                .is_some_and(|e| Rect::from_min_size(egui::pos2(e.rect[0], e.rect[1]), egui::vec2(e.rect[2], e.rect[3])).contains(p))
-        });
+                app.auto
+                    .elements
+                    .iter()
+                    .find(|e| e.id == "panel.Timeline")
+                    .is_some_and(|e| Rect::from_min_size(egui::pos2(e.rect[0], e.rect[1]), egui::vec2(e.rect[2], e.rect[3])).contains(p))
+            });
 
         let at = if proj.is_empty() && !over_timeline {
             ctx.input(|i| i.pointer.hover_pos()).filter(|p| viewer.is_some_and(|v| v.contains(*p))).and_then(|p| crate::panels::viewer::screen_to_comp(&ctx, p))