ui: a file dropped on a floating Timeline joins that composition (#2661)

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

crates/ui-egui/src/dock_ui.rs

@@ -530,6 +530,11 @@ 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)) {
+            self.forwarded.dropped_on_timeline = true;
+        }
         self.forwarded.files.extend(files.into_iter().flat_map(|window| window.dropped));
         if !self.forwarded.events.is_empty() || !self.forwarded.files.is_empty() {
             ctx.request_repaint();

crates/ui-egui/src/lib.rs

@@ -442,6 +442,10 @@ impl FileDialogsUp {
 pub(crate) struct ForwardedInput {
     pub(crate) events: Vec<egui::Event>,
     pub(crate) files: Vec<egui::DroppedFileHandle>,
+    /// Files handed over by a floating window whose panel under the pointer was the Timeline. The
+    /// paths lose the window they came from, so this keeps the one thing the import still needs
+    /// (#2661); each drop clears it.
+    pub(crate) dropped_on_timeline: bool,
 }
 
 /// Record the scale the viewer drew at (called by the viewer panel each pass).

crates/ui-egui/src/prefs_live.rs

@@ -63,6 +63,10 @@ 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).
+    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| {
         let l = p.to_ascii_lowercase();
         l.ends_with(".ecproj") || l.ends_with(".ecprojx")
@@ -88,7 +92,8 @@ pub fn dropped_files(app: &mut EffectcraftApp, ui: &egui::Ui, bounds: Rect) {
 
         // Dropping a file on the Timeline adds it to the composition the panel shows, as it does
         // on the viewer (#2588); the import decides the layer's position.
-        let over_timeline = ctx.input(|i| i.pointer.hover_pos()).is_some_and(|p| {
+        let over_timeline = handed_by_a_floating_window
+            || ctx.input(|i| i.pointer.hover_pos()).is_some_and(|p| {
             app.auto
                 .elements
                 .iter()