View backgrounds: reference blend, image adjust, layouts, cleanup, style name

- Gradients: the middle colour sits (horizon - 0.5) viewport widths from the
  centre and blends over height viewport heights each side; two colours
  blend over a viewport height each side.
- Image backgrounds: offset in device pixels (right, down), negative scale
  mirrors, fitted with aspect ratio covers the viewport; the dialog keeps an
  image's offset and scale.
- Layouts: a model-space view restored on a sheet asks for the viewport,
  enters it and gives it the view's camera, background and visual style;
  inside a viewport the view goes there; a paper-space view's background is
  kept on the sheet viewport but not drawn; floating viewports draw their
  background.
- Background objects no view or viewport uses any more are erased; a view
  without a background restored where the viewport already is leaves the
  viewport's background.
- The viewport's named visual style (Realistic, ...) shows by name and the
  render-mode picker records its style on the viewport record.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

src/app/view/controls.rs

@@ -30,6 +30,7 @@ pub(super) fn viewport_controls<'a>(
     tile_count: usize,
     render_mode_menu_open: bool,
     render_mode_preview: Option<codec::entities::ViewportRenderMode>,
+    style_name: Option<String>,
 ) -> Element<'a, Message> {
     let render_modes: Vec<RenderModeChoice> = crate::modules::view::visual_style::VISUAL_STYLES
         .iter()
@@ -98,7 +99,7 @@ pub(super) fn viewport_controls<'a>(
     // flyout keeps the current style unchanged while hovering; a click commits.
     let picker_head = button(
         row![
-            text(RenderModeChoice(render_mode).to_string()).size(11),
+            text(style_name.unwrap_or_else(|| RenderModeChoice(render_mode).to_string())).size(11),
             crate::ui::icons::themed_arrow_toggle(render_mode_menu_open, 9.0),
         ]
         .spacing(6)
@@ -379,7 +380,7 @@ mod tests {
     #[test]
     fn test_viewport_controls_construction() {
         for style in crate::modules::view::visual_style::VISUAL_STYLES {
-            let _el = viewport_controls(style.mode, true, true, true, 1, false, None);
+            let _el = viewport_controls(style.mode, true, true, true, 1, false, None, None);
             let _el_open = viewport_controls(
                 style.mode,
                 false,
@@ -388,6 +389,7 @@ mod tests {
                 2,
                 true,
                 Some(M::Wireframe3D),
+                None,
             );
         }
     }

src/app/view/mod.rs

@@ -1297,6 +1297,18 @@ bg={bg_ms:.1}ms n={view_count}"
                 let rect = tab.scene.active_model_tile_bounds(vw, vh);
                 // Unified control chip: split buttons + render-mode picker +
                 // grid / grid-snap toggles, for the active Model tile.
+                // A named style (Realistic, …) the tile draws as shows by name.
+                let style_name = match tab.scene.document.objects.get(&tab.scene.active_visual_style()) {
+                    Some(codec::objects::ObjectType::VisualStyle(style)) => {
+                        match crate::modules::view::visual_style::mode_for_style_name(&style.description) {
+                            Some((mode, true)) if mode == tab.render_mode => {
+                                Some(crate::t!(style.description.as_str()).into_owned())
+                            }
+                            _ => None,
+                        }
+                    }
+                    _ => None,
+                };
                 let bar = viewport_controls(
                     tab.render_mode,
                     self.show_grid,
@@ -1305,6 +1317,7 @@ bg={bg_ms:.1}ms n={view_count}"
                     tab.scene.model_tiles.borrow().len(),
                     self.render_mode_menu_open,
                     self.render_mode_preview,
+                    style_name,
                 );
                 // Adaptive: DensitySwap measures the bar's real width every frame
                 // (reported into `render_bar_w`, which the ViewCube reads to decide
@@ -1397,6 +1410,7 @@ bg={bg_ms:.1}ms n={view_count}"
                     0,
                     self.render_mode_menu_open,
                     self.render_mode_preview,
+                    None,
                 );
                 let adaptive: Element<'_, Message> = DensitySwap::new(vec![
                     iced::widget::opaque(bar),