feat(display): add model lineweight scale

src/app/mod.rs

@@ -492,6 +492,8 @@ pub(super) struct OpenCADStudio {
     crosshair_color: Option<[u8; 3]>,
     /// Editable Options buffer for the crosshair colour.
     crosshair_color_input: String,
+    /// Model-space lineweight preview scale, in percent (25..=200).
+    lineweight_display_scale: i32,
     /// Isometric drafting state and active axis pair.
     isometric_drafting: bool,
     iso_plane: settings::IsoPlane,
@@ -1910,6 +1912,8 @@ pub enum Message {
     PickBoxChanged(i32),
     /// Set CURSORTYPE from Options.
     CursorTypeChanged(settings::CursorType),
+    /// Set the model-space lineweight preview scale from Options.
+    LineweightDisplayScaleChanged(i32),
     /// Edit the optional crosshair RGB value; blank restores automatic contrast.
     CrosshairColorChanged(String),
     /// Set the default type/version used when first saving a new drawing.
@@ -3280,6 +3284,7 @@ impl OpenCADStudio {
             cursor_type: settings::CursorType::Crosshair,
             crosshair_color: None,
             crosshair_color_input: String::new(),
+            lineweight_display_scale: 100,
             isometric_drafting: false,
             iso_plane: settings::IsoPlane::Left,
             snap_angle_deg: 0.0,

src/app/settings.rs

@@ -164,6 +164,8 @@ pub struct UserSettings {
     pub cursor_type: CursorType,
     /// Explicit crosshair RGB. `None` keeps automatic background contrast.
     pub crosshair_color: Option<[u8; 3]>,
+    /// Model-space lineweight preview scale as a percentage.
+    pub lineweight_display_scale: i32,
     /// Isometric drafting changes the grid and crosshair to the active axis pair.
     pub isometric_drafting: bool,
     pub iso_plane: IsoPlane,
@@ -282,6 +284,7 @@ impl Default for UserSettings {
             pick_box: 3,
             cursor_type: CursorType::Crosshair,
             crosshair_color: None,
+            lineweight_display_scale: 100,
             isometric_drafting: false,
             iso_plane: IsoPlane::Left,
             snap_angle_deg: 0.0,

src/app/update/command.rs

@@ -124,7 +124,7 @@ pub(super) fn on_tab_close(&mut self, idx: usize) -> Task<Message> {
                     self.tab_counter += 1;
                     self.tabs[0] = crate::app::document::DocumentTab::new_drawing(self.tab_counter);
                     self.active_tab = 0;
-                    self.apply_bg_default(0);
+                    self.apply_display_defaults(0);
                 } else {
                     self.tabs.remove(idx);
                     if self.active_tab >= self.tabs.len() {

src/app/update/dialog.rs

@@ -210,7 +210,7 @@ pub(super) fn on_ribbon_tool_click(&mut self, tool_id: String, event: ModuleEven
                             self.tabs[0] =
                                 crate::app::document::DocumentTab::new_drawing(self.tab_counter);
                             self.active_tab = 0;
-                            self.apply_bg_default(0);
+                            self.apply_display_defaults(0);
                         } else {
                             self.tabs.remove(idx);
                             if self.active_tab >= self.tabs.len() {

src/app/update/file.rs

@@ -364,6 +364,7 @@ impl OpenCADStudio {
             pick_box: self.pick_box,
             cursor_type: self.cursor_type,
             crosshair_color: self.crosshair_color,
+            lineweight_display_scale: self.lineweight_display_scale,
             isometric_drafting: self.isometric_drafting,
             iso_plane: self.iso_plane,
             snap_angle_deg: self.snap_angle_deg,
@@ -416,6 +417,7 @@ impl OpenCADStudio {
             .crosshair_color
             .map(crate::app::config::rgb_to_hex)
             .unwrap_or_default();
+        self.lineweight_display_scale = s.lineweight_display_scale.clamp(25, 200);
         self.isometric_drafting = s.isometric_drafting;
         self.iso_plane = s.iso_plane;
         self.snap_angle_deg = if s.snap_angle_deg.is_finite() {
@@ -469,11 +471,10 @@ impl OpenCADStudio {
             .take(200)
             .map(|(k, v)| (k.clone(), *v))
             .collect();
-        // Push the restored background onto every drawing tab that exists now
-        // (the start tab and any initial drawing). Tabs created later pick it
-        // up via `apply_bg_default` at their construction site.
+        // Push restored display defaults onto every drawing tab that exists now.
+        // Tabs created later pick them up at their construction site.
         for idx in 0..self.tabs.len() {
-            self.apply_bg_default(idx);
+            self.apply_display_defaults(idx);
         }
         self.rebuild_ribbon_modules();
     }
@@ -596,19 +597,18 @@ impl OpenCADStudio {
         h.object_snap_mode = osmode;
     }
 
-    /// Apply the persisted default background(s) to tab `idx`. No-op for the
-    /// start tab or when no default is set. Refreshes the tab's cached wires
-    /// and meshes so background-adaptive colours pick up the change.
-    pub(in crate::app) fn apply_bg_default(&mut self, idx: usize) {
+    /// Apply persisted viewport display defaults to tab `idx`.
+    pub(in crate::app) fn apply_display_defaults(&mut self, idx: usize) {
         let bg = self.default_bg_color;
         let paper_bg = self.default_paper_bg_color;
-        if bg.is_none() && paper_bg.is_none() {
-            return;
-        }
         let tab = &mut self.tabs[idx];
         if tab.is_start {
             return;
         }
+        tab.scene.model_lineweight_scale = self.lineweight_display_scale as f32 / 100.0;
+        if bg.is_none() && paper_bg.is_none() {
+            return;
+        }
         if let Some(c) = bg {
             tab.bg_color = Some(c);
             tab.scene.bg_color = c;
@@ -1286,7 +1286,7 @@ pub(super) fn on_open_file(&mut self) -> Task<Message> {
                     self.tabs.push(new_tab);
                     let idx = self.tabs.len() - 1;
                     self.active_tab = idx;
-                    self.apply_bg_default(idx);
+                    self.apply_display_defaults(idx);
                     idx
                 };
 
@@ -2381,7 +2381,7 @@ pub(super) fn on_open_file(&mut self) -> Task<Message> {
         self.tab_counter += 1;
         self.tabs[i] = crate::app::document::DocumentTab::new_drawing(self.tab_counter);
         self.active_tab = i;
-        self.apply_bg_default(i);
+        self.apply_display_defaults(i);
         self.update(Message::OpenPathPicked(Some((
             conflict.path,
             metadata.len(),

src/app/update/mod.rs

@@ -1271,7 +1271,7 @@ impl OpenCADStudio {
                 // creating one doesn't silently reset them (its header default is
                 // 0 = no snaps); saving then persists them into the file.
                 self.stamp_header_sysvars(idx);
-                self.apply_bg_default(idx);
+                self.apply_display_defaults(idx);
                 self.sync_ribbon_layers();
                 self.sync_ribbon_styles();
                 // #21: reset ribbon Color / Linetype / Lineweight to the
@@ -5787,6 +5787,16 @@ impl OpenCADStudio {
                 Task::none()
             }
 
+            Message::LineweightDisplayScaleChanged(value) => {
+                self.lineweight_display_scale = value.clamp(25, 200);
+                let scale = self.lineweight_display_scale as f32 / 100.0;
+                for tab in &mut self.tabs {
+                    tab.scene.model_lineweight_scale = scale;
+                }
+                self.persist_settings_if_changed();
+                Task::none()
+            }
+
             Message::CrosshairColorChanged(value) => {
                 self.crosshair_color_input = value.clone();
                 if value.trim().is_empty() {

src/app/view/modal.rs

@@ -189,6 +189,7 @@ impl OpenCADStudio {
                         self.cursor_type,
                         self.crosshair_color,
                         &self.crosshair_color_input,
+                        self.lineweight_display_scale,
                         flow,
                     )
                 },

src/scene/mod.rs

@@ -1469,6 +1469,8 @@ pub struct Scene {
     /// Whether entity transparency is honoured on screen. When false the
     /// wire shader forces every line opaque (a uniform toggle, no retessellate).
     pub transparency_display: bool,
+    /// User-adjustable model-space lineweight preview multiplier.
+    pub model_lineweight_scale: f32,
     /// Selection filter: entity-type names excluded from interactive picking.
     /// Empty = every type is selectable.
     pub selection_filter: HashSet<String>,
@@ -1878,6 +1880,7 @@ impl Scene {
             refedit_keep: None,
             hover_highlight: None,
             transparency_display: true,
+            model_lineweight_scale: 1.0,
             selection_filter: HashSet::default(),
             preview_wires: vec![],
             preview_hatches: Arc::new(Vec::new()),

src/scene/pipeline/uniforms.rs

@@ -25,8 +25,8 @@ pub struct Uniforms {
     /// zooming inside MSPACE changes one scalar instead of re-tessellating and
     /// re-uploading every dashed wire.
     pub linetype_scale: f32,
-    /// Multiplier for screen-space lineweights. Model space keeps `1.0`;
-    /// paper layouts derive it from the current paper zoom.
+    /// Multiplier for screen-space lineweights. Model space uses the user's
+    /// preview scale; paper layouts derive it from the current paper zoom.
     pub lineweight_scale: f32,
 
     // ── Relative-to-eye (double-single) additions ───────────────────────────

src/scene/view/render.rs

@@ -3847,7 +3847,9 @@ impl Scene {
             full_bounds,
             self.document.header.lineweight_display || display_plot_lineweights,
         );
-        if self.current_layout != "Model" {
+        if self.current_layout == "Model" {
+            uniforms.lineweight_scale = self.model_lineweight_scale;
+        } else {
             let paper_per_pixel = 2.0 * self.camera.borrow().ortho_size() / canvas.1.max(1.0);
             let paper_units_per_mm = self.paper_space_unit_factor() as f32;
             uniforms.lineweight_scale = paper_units_per_mm / paper_per_pixel / MM_TO_PX;

src/ui/window/options.rs

@@ -39,6 +39,7 @@ pub fn view_window<'a>(
     cursor_type: CursorType,
     crosshair_color: Option<[u8; 3]>,
     crosshair_color_input: &'a str,
+    lineweight_display_scale: i32,
     sizing: crate::ui::modal::ModalSizing,
 ) -> Element<'a, Message> {
     let selected_format = crate::io::SAVE_FORMAT_OPTIONS
@@ -265,6 +266,28 @@ pub fn view_window<'a>(
         text(crate::t!("Leave the color blank to keep automatic viewport contrast."))
             .size(11)
             .width(sizing.width),
+        Space::new().height(24),
+        text(crate::t!("Lineweight")).size(15),
+        Space::new().height(10),
+        row![
+            text(crate::t!("Model display scale")).size(12).width(140),
+            slider(
+                25..=200,
+                lineweight_display_scale.clamp(25, 200),
+                Message::LineweightDisplayScaleChanged,
+            )
+            .step(1)
+            .width(Fill),
+            text(format!("{}%", lineweight_display_scale.clamp(25, 200)))
+                .size(11)
+                .width(44),
+        ]
+        .spacing(10)
+        .align_y(iced::Center),
+        Space::new().height(6),
+        text(crate::t!("Changes the on-screen width in Model without affecting plotted output."))
+            .size(11)
+            .width(sizing.width),
     ]
     .spacing(0)
     .width(sizing.width);