feat(ui): migrate the last dialogs to modals — fully single-window (Plan B)

Move the unsaved-changes prompt, the Save As browser and the
file-association prompt onto `active_modal` / `modal_content`, reusing
their existing open/close helpers (now just set/clear active_modal). The
daemon `view` no longer dispatches per window — every dialog is an
in-canvas modal, so the app is single-window on native and web alike.

`close_active_modal` handles their ✕: the unsaved prompt cancels the
pending close, the association prompt records that it was answered.

Native + web build; 75 tests pass.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/app/mod.rs

@@ -606,6 +606,9 @@ pub enum ModalKind {
     MlStyle,
     MLeaderStyle,
     DimStyle,
+    Unsaved,
+    SaveDialog,
+    AssocPrompt,
 }
 
 /// Identifies a DimStyle field that can be edited in the dialog.
@@ -1687,18 +1690,10 @@ impl OpenCADStudio {
         // One-time prompt offering to make Open CAD Studio the default app for
         // .dwg / .dxf. Shown only on the first launch that hasn't answered it
         // yet; the flag is persisted so we never ask twice.
-        let assoc_prompt: Task<Message> = if s.default_assoc_prompted {
+        let assoc_prompt: Task<Message> = Task::none();
-            Task::none()
+        if !s.default_assoc_prompted {
-        } else {
+            s.active_modal = Some(ModalKind::AssocPrompt);
-            let (id, open) = window::open(window::Settings {
+        }
-                size: iced::Size::new(440.0, 210.0),
-                resizable: false,
-                level: window::Level::AlwaysOnTop,
-                ..Default::default()
-            });
-            s.assoc_prompt_window = Some(id);
-            open.map(|_| Message::Noop)
-        };
         (
             s,
             Task::batch([open_main, check_update, focus_cmd, cli_open, assoc_prompt]),

src/app/update.rs

@@ -117,6 +117,9 @@ impl OpenCADStudio {
                 self.ribbon.deactivate_tool_if("KEYBOARD");
             }
             Some(About) => self.ribbon.deactivate_tool_if("ABOUT"),
+            // Dismissing these via ✕ is the cancel/decline path.
+            Some(Unsaved) => self.pending_close = None,
+            Some(AssocPrompt) => self.mark_assoc_prompted(),
             _ => {}
         }
         self.active_modal = None;
@@ -5784,24 +5787,16 @@ impl OpenCADStudio {
             }
             Message::AssocPromptYes => {
                 self.mark_assoc_prompted();
-                let close = if let Some(id) = self.assoc_prompt_window.take() {
+                self.active_modal = None;
-                    window::close(id)
+                Task::perform(
-                } else {
-                    Task::none()
-                };
-                let run = Task::perform(
                     crate::io::file_association::set_default_app(),
                     Message::AssocResult,
-                );
+                )
-                Task::batch([close, run])
             }
             Message::AssocPromptNo => {
                 self.mark_assoc_prompted();
-                if let Some(id) = self.assoc_prompt_window.take() {
+                self.active_modal = None;
-                    window::close(id)
+                Task::none()
-                } else {
-                    Task::none()
-                }
             }
             Message::AssocResult(result) => {
                 match result {
@@ -8534,44 +8529,27 @@ impl OpenCADStudio {
             self.save_dialog_filename = format!("{}.{ext}", self.tabs[tab_idx].tab_display_name());
         }
         self.save_dialog_entries = crate::io::read_dir_entries(&self.save_dialog_folder.clone());
-        let (id, task) = window::open(window::Settings {
+        self.active_modal = Some(super::ModalKind::SaveDialog);
-            size: iced::Size::new(560.0, 480.0),
+        Task::none()
-            resizable: true,
-            level: window::Level::AlwaysOnTop,
-            ..Default::default()
-        });
-        self.save_dialog_window = Some(id);
-        task.map(|_| Message::Noop)
     }
 
     fn close_save_dialog_window(&mut self) -> Task<Message> {
-        if let Some(id) = self.save_dialog_window.take() {
+        if self.active_modal == Some(super::ModalKind::SaveDialog) {
-            window::close(id)
+            self.active_modal = None;
-        } else {
-            Task::none()
         }
+        Task::none()
     }
 
     fn open_unsaved_dialog_window(&mut self) -> Task<Message> {
-        if let Some(id) = self.unsaved_dialog_window {
+        self.active_modal = Some(super::ModalKind::Unsaved);
-            return window::gain_focus(id);
+        Task::none()
-        }
-        let (id, task) = window::open(window::Settings {
-            size: iced::Size::new(420.0, 155.0),
-            resizable: false,
-            level: window::Level::AlwaysOnTop,
-            ..Default::default()
-        });
-        self.unsaved_dialog_window = Some(id);
-        task.map(|_| Message::Noop)
     }
 
     fn close_unsaved_dialog_window(&mut self) -> Task<Message> {
-        if let Some(id) = self.unsaved_dialog_window.take() {
+        if self.active_modal == Some(super::ModalKind::Unsaved) {
-            window::close(id)
+            self.active_modal = None;
-        } else {
-            Task::none()
         }
+        Task::none()
     }
 
     pub(super) fn load_textstyle_bufs(&mut self, tab: usize) {

src/app/view.rs

@@ -40,35 +40,9 @@ impl std::fmt::Display for RenderModeChoice {
 impl OpenCADStudio {
     pub fn view(&self, window_id: window::Id) -> Element<'_, Message> {
         // ── Floating panel windows ─────────────────────────────────────────
-        if Some(window_id) == self.assoc_prompt_window {
+        // All dialogs are in-canvas modals now (Plan B); view_main stacks the
-            return default_assoc_dialog_window();
+        // active one. `window_id` is unused — there is only the main window.
-        }
+        let _ = window_id;
-        if Some(window_id) == self.unsaved_dialog_window {
-            let tab_name = match &self.pending_close {
-                Some(super::PendingClose::Tab(idx)) => self
-                    .tabs
-                    .get(*idx)
-                    .map(|t| t.tab_display_name())
-                    .unwrap_or_default(),
-                Some(super::PendingClose::Quit) => self
-                    .tabs
-                    .iter()
-                    .find(|t| t.dirty)
-                    .map(|t| t.tab_display_name())
-                    .unwrap_or_default(),
-                None => String::new(),
-            };
-            return unsaved_changes_dialog_window(&tab_name);
-        }
-        if Some(window_id) == self.save_dialog_window {
-            return save_as_dialog_window(
-                &self.save_dialog_filename,
-                &self.save_dialog_folder,
-                &self.save_dialog_entries,
-                &self.save_dialog_format,
-            );
-        }
-
         self.view_main()
     }
 
@@ -1543,6 +1517,34 @@ impl OpenCADStudio {
                 &self.style_rename_buf,
             ), 720, 560)
             }
+            super::ModalKind::AssocPrompt => sized(default_assoc_dialog_window(), 440, 210),
+            super::ModalKind::Unsaved => {
+                let tab_name = match &self.pending_close {
+                    Some(super::PendingClose::Tab(idx)) => self
+                        .tabs
+                        .get(*idx)
+                        .map(|t| t.tab_display_name())
+                        .unwrap_or_default(),
+                    Some(super::PendingClose::Quit) => self
+                        .tabs
+                        .iter()
+                        .find(|t| t.dirty)
+                        .map(|t| t.tab_display_name())
+                        .unwrap_or_default(),
+                    None => String::new(),
+                };
+                sized(unsaved_changes_dialog_window(&tab_name), 420, 160)
+            }
+            super::ModalKind::SaveDialog => sized(
+                save_as_dialog_window(
+                    &self.save_dialog_filename,
+                    &self.save_dialog_folder,
+                    &self.save_dialog_entries,
+                    &self.save_dialog_format,
+                ),
+                560,
+                480,
+            ),
         })
     }