feat(statusbar): scrollable layout tabs + layout-list dropdown (#199)

Keep the right-side status-bar tools from being pushed off the bar when a
drawing has many layouts: the layout tabs now live in a horizontal scrollable
that only takes the space left between the menu and the tools, with ‹ › arrows
(and the mouse wheel) to scroll them.

Repurpose the leftmost hamburger — which previously fired a no-op MENU command
— to open a dropdown listing Model and every layout (scrollable, current
highlighted); picking one switches to it, an outside click dismisses it.

Co-Authored-By: Claude Opus 4.8 <[email protected]>

src/app/mod.rs

@@ -202,6 +202,8 @@ pub(super) struct OpenCADStudio {
     scale_popup_open: bool,
     /// True while the status-bar customization menu is open.
     statusbar_menu_open: bool,
+    /// True while the leftmost hamburger's Model/layout list dropdown is open.
+    layout_list_open: bool,
     /// True while the drawing-units picker is open.
     units_popup_open: bool,
     /// True while the Isolate pill's action menu is open.
@@ -1011,6 +1013,9 @@ pub enum Message {
     OpenRecent(PathBuf),
     /// Open a URL in the system browser (start-page intro video, links).
     OpenUrl(String),
+    /// Scroll the status-bar layout-tab strip horizontally by `delta` px
+    /// (negative = left). Driven by the ‹ › arrows next to the tabs.
+    ScrollLayoutTabs(f32),
     /// Drop a path from the recent-documents list.
     RecentRemove(PathBuf),
     /// User clicked Cancel on the loading overlay. The parser thread keeps
@@ -1215,6 +1220,10 @@ pub enum Message {
     ToggleScalePopup,
     /// Close the scale picker popup.
     CloseScalePopup,
+    /// Toggle the leftmost hamburger's Model/layout list dropdown.
+    ToggleLayoutList,
+    /// Close the Model/layout list dropdown.
+    CloseLayoutList,
     /// Toggle the status-bar customization menu open/closed.
     ToggleStatusBarMenu,
     /// Close the status-bar customization menu.
@@ -1794,6 +1803,7 @@ impl OpenCADStudio {
             snap_popup_open: false,
             scale_popup_open: false,
             statusbar_menu_open: false,
+            layout_list_open: false,
             units_popup_open: false,
             isolate_popup_open: false,
             selection_filter_popup_open: false,

src/app/update/mod.rs

@@ -213,6 +213,11 @@ impl OpenCADStudio {
                 Task::none()
             }
 
+            Message::ScrollLayoutTabs(dx) => iced::widget::operation::scroll_by(
+                iced::advanced::widget::Id::new(crate::ui::statusbar::LAYOUT_TABS_SCROLL_ID),
+                iced::widget::scrollable::AbsoluteOffset { x: dx, y: 0.0 },
+            ),
+
             Message::OpenRecent(path) => {
                 // Recents are read from disk every save → the path may be
                 // stale. Skip silently if the file no longer exists; the
@@ -1336,6 +1341,14 @@ impl OpenCADStudio {
                 self.scale_popup_open = false;
                 Task::none()
             }
+            Message::ToggleLayoutList => {
+                self.layout_list_open ^= true;
+                Task::none()
+            }
+            Message::CloseLayoutList => {
+                self.layout_list_open = false;
+                Task::none()
+            }
             Message::ToggleStatusBarMenu => {
                 self.statusbar_menu_open ^= true;
                 Task::none()
@@ -1946,7 +1959,10 @@ impl OpenCADStudio {
                 Task::none()
             }
 
-            Message::LayoutSwitch(name) => self.on_layout_switch(name),
+            Message::LayoutSwitch(name) => {
+                self.layout_list_open = false;
+                self.on_layout_switch(name)
+            }
 
             Message::LayoutCreate => self.on_layout_create(),
 

src/app/view/mod.rs

@@ -1222,6 +1222,15 @@ impl OpenCADStudio {
             iced::widget::Space::new().width(0).height(0).into()
         };
 
+        let layout_list_layer: Element<'_, Message> = if self.layout_list_open && !tab.is_start {
+            crate::ui::statusbar::statusbar_menu::layout_list_overlay(
+                &tab.scene.layout_names(),
+                &tab.scene.current_layout,
+            )
+        } else {
+            iced::widget::Space::new().width(0).height(0).into()
+        };
+
         let units_layer: Element<'_, Message> = if self.units_popup_open {
             crate::ui::popup::units_popup::units_popup_overlay(tab.scene.document.header.insertion_units)
         } else {
@@ -1286,6 +1295,7 @@ impl OpenCADStudio {
             snap_layer,
             scale_layer,
             statusbar_menu_layer,
+            layout_list_layer,
             units_layer,
             isolate_layer,
             sel_filter_layer,