Fix #1694: a file that finishes opening waits while a dialog is open

A document opened off the UI thread became the active one as soon as it was
ready, also under an open dialog, whose OK acts on the active document: Save
As options confirmed after another file had finished opening wrote that
file's art under the first document's name. Files that are ready now wait
until the dialog is closed.

crates/ui-egui/src/opening.rs

@@ -68,8 +68,14 @@ pub fn start(app: &mut VectorcraftApp, path: &str, bytes: Vec<u8>) -> Result<Val
     Ok(json!({ "background": true, "status": status }))
 }
 
-/// Open the files that are ready (each frame).
+/// Open the files that are ready (each frame). Not while a dialog is open: a document that opens
+/// becomes the active one, and the dialog's OK acts on the active document (#1694: Save As
+/// options confirmed after another file had finished opening saved that file's art under the
+/// first one's name). The files wait, their status line too, until the dialog is closed.
 pub fn poll(app: &mut VectorcraftApp) {
+    if app.ui.dialog.is_some() {
+        return;
+    }
     let mut i = 0;
     while let Some(p) = app.opening.pending.get(i) {
         let r = match p.done.try_recv() {
@@ -108,6 +114,32 @@ mod tests {
     use super::*;
     use crate::Services;
 
+    /// #1694: a file that finishes opening while a dialog is up waits for it to close, so the
+    /// dialog's document stays the active one.
+    #[test]
+    fn a_file_ready_while_a_dialog_is_open_waits_for_it_to_close() {
+        let mut app = VectorcraftApp::new(Session::new(), Services::default());
+        app.run("file.new", json!({"width": 100, "height": 80})).unwrap();
+        let (first, before) = (app.session.doc().unwrap().uid, app.session.documents().len());
+        app.ui.dialog = Some(crate::state::Dialog::new(crate::dialogs::save_options::KIND, json!({"path": "/art/First.vectorcraft"})));
+        start(&mut app, "/art/Second.vectorcraft", vectorcraft_format::save(&vectorcraft_doc::Document::new(120.0, 80.0), false)).unwrap();
+        let t0 = std::time::Instant::now();
+        while t0.elapsed().as_millis() < 400 {
+            poll(&mut app);
+            std::thread::yield_now();
+        }
+        assert_eq!((app.session.documents().len(), app.session.doc().unwrap().uid), (before, first), "still the dialog's document");
+        assert_eq!(app.opening.pending.len(), 1);
+        app.ui.dialog = None;
+        let t0 = std::time::Instant::now();
+        while !app.opening.pending.is_empty() && t0.elapsed().as_secs() < 30 {
+            poll(&mut app);
+            std::thread::yield_now();
+        }
+        assert_eq!(app.session.documents().len(), before + 1);
+        assert_eq!(app.session.doc().unwrap().path.as_deref(), Some("/art/Second.vectorcraft"));
+    }
+
     #[test]
     fn a_file_read_off_the_ui_thread_opens_as_one_read_at_once() {
         let mut app = VectorcraftApp::new(Session::new(), Services::default());