Layouts: a viewport on first opening (LAYOUTCREATEVIEWPORT)

A layout opened for the first time - one whose sheet viewport had to be
made, or one created in this session - gets a viewport centred on the
printable area, 0.8 of its width and height, zoomed to the model's
extents, while LAYOUTCREATEVIEWPORT is on. The profile variable takes
ON/OFF or 1/0 and is kept with the settings.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/app/update/file.rs

@@ -796,6 +796,7 @@ impl OpenCADStudio {
             surface_associativity: crate::scene::model::sweep_model::surface_associativity(),
             ucs_ortho: crate::modules::view::view_cmd::ucs_ortho(),
             ucs_view: crate::modules::view::view_cmd::ucs_view(),
+            layout_create_viewport: crate::scene::layout_create_viewport(),
             ncopy_bind: self.ncopy_bind,
             cursor_type: self.cursor_type,
             crosshair_color: self.crosshair_color,
@@ -911,6 +912,7 @@ impl OpenCADStudio {
         crate::scene::model::sweep_model::set_surface_associativity(s.surface_associativity);
         crate::modules::view::view_cmd::set_ucs_ortho(s.ucs_ortho);
         crate::modules::view::view_cmd::set_ucs_view(s.ucs_view);
+        crate::scene::set_layout_create_viewport(s.layout_create_viewport);
         self.ncopy_bind = s.ncopy_bind;
         self.cursor_type = s.cursor_type;
         self.crosshair_color = s.crosshair_color;

src/app/update/viewport.rs

@@ -6549,10 +6549,17 @@ properties={:.1}ms picked={}",
                 self.tabs[i].scene.ensure_sheet_viewport(&new_name);
                 let switch_task = self.on_layout_switch(new_name.clone());
                 self.tabs[i].scene.fit_all();
-                self.command_line.push_output(
-                    crate::tf!("Layout \"{new_name}\" created — use MVIEW to add a viewport")
-                        .as_ref(),
-                );
+                // Opened, it already has its first viewport unless
+                // LAYOUTCREATEVIEWPORT is off.
+                if crate::scene::layout_create_viewport() {
+                    let name = new_name.clone();
+                    self.command_line.push_output(crate::tf!("Layout '{name}' created.").as_ref());
+                } else {
+                    self.command_line.push_output(
+                        crate::tf!("Layout \"{new_name}\" created — use MVIEW to add a viewport")
+                            .as_ref(),
+                    );
+                }
                 // The option that greets every new layout with its page setup.
                 let switch_task = if self.plot_dialog.page_setup_on_new_layout {
                     Task::batch([switch_task, self.on_plot_dialog_open()])