fix(style): block edits to xref-dependent dimstyles

src/app/update/mod.rs

@@ -12050,7 +12050,9 @@ impl OpenCADStudio {
             Message::DimStyleDialogApply => {
                 let i = self.active_tab;
                 self.apply_dimstyle_bufs(i);
-                self.style_stage_commit();
+                if !self.selected_dimstyle_is_read_only() {
+                    self.style_stage_commit();
+                }
                 Task::none()
             }
             Message::DimStyleDialogSelect(name) => {
@@ -12073,6 +12075,9 @@ impl OpenCADStudio {
             Message::DimStyleDialogCopy => self.style_copy(crate::app::StyleKind::Dim),
             Message::DimStyleDialogSetCurrent => {
                 // Staged: persists on Apply.
+                if self.selected_dimstyle_is_read_only() {
+                    return Task::none();
+                }
                 let i = self.active_tab;
 
                 self.tabs[i].scene.document.header.current_dimstyle_name =
@@ -12093,6 +12098,9 @@ impl OpenCADStudio {
                 Task::none()
             }
             Message::DsToggle(field) => {
+                if self.selected_dimstyle_is_read_only() {
+                    return Task::none();
+                }
                 let separate_arrows = field == crate::app::DsField::Dimsah;
                 self.apply_ds_toggle(field);
                 if separate_arrows && self.ds_dimsah {
@@ -12114,6 +12122,9 @@ impl OpenCADStudio {
                 Task::none()
             }
             Message::DsToleranceMode(mode) => {
+                if self.selected_dimstyle_is_read_only() {
+                    return Task::none();
+                }
                 self.ds_dimlim = mode == "limits";
                 self.ds_dimtol = matches!(mode.as_str(), "symmetrical" | "deviation");
                 if mode == "symmetrical" {
@@ -12128,6 +12139,9 @@ impl OpenCADStudio {
                 Task::none()
             }
             Message::DsZeroBase(field, base) => {
+                if self.selected_dimstyle_is_read_only() {
+                    return Task::none();
+                }
                 let current = match &field {
                     crate::app::DsField::Dimzin => &self.ds_dimzin,
                     crate::app::DsField::Dimaltz => &self.ds_dimaltz,
@@ -12142,6 +12156,9 @@ impl OpenCADStudio {
                 Task::none()
             }
             Message::DsZeroFlag(field, bit) => {
+                if self.selected_dimstyle_is_read_only() {
+                    return Task::none();
+                }
                 let current = match &field {
                     crate::app::DsField::Dimzin => &self.ds_dimzin,
                     crate::app::DsField::Dimaltz => &self.ds_dimaltz,
@@ -12156,6 +12173,9 @@ impl OpenCADStudio {
                 Task::none()
             }
             Message::DsCenterMarkMode(mode) => {
+                if self.selected_dimstyle_is_read_only() {
+                    return Task::none();
+                }
                 let size = self.ds_dimcen.trim().parse::<f64>().unwrap_or(0.09).abs();
                 self.ds_dimcen = match mode.as_str() {
                     "mark" => size.max(f64::EPSILON).to_string(),
@@ -12165,6 +12185,9 @@ impl OpenCADStudio {
                 Task::none()
             }
             Message::DsColorMore(field) => {
+                if self.selected_dimstyle_is_read_only() {
+                    return Task::none();
+                }
                 self.ds_color_open = if self.ds_color_open.as_ref() == Some(&field) {
                     None
                 } else {

src/app/update/style.rs

@@ -21,6 +21,18 @@ use iced::time::Instant;
 use iced::{mouse, Point, Task};
 
 impl OpenCADStudio {
+    pub(in crate::app) fn selected_dimstyle_is_read_only(&self) -> bool {
+        let Some(style) = self.tabs[self.active_tab]
+            .scene
+            .document
+            .dim_styles
+            .get(&self.dimstyle_selected)
+        else {
+            return true;
+        };
+        style.xref_dependent || style.name.contains('|')
+    }
+
     pub(in crate::app) fn mlstyle_mut(
         &mut self,
         tab: usize,
@@ -364,6 +376,17 @@ impl OpenCADStudio {
     pub(in crate::app) fn apply_dimstyle_bufs(&mut self, tab: usize) {
         let doc = &mut self.tabs[tab].scene.document;
 
+        // Merged xref dimstyles are identified by their `xref|style` name.
+        // The codec's dependency bit is cleared during merge, so use the
+        // stable imported-name marker here as well as the DWG/DXF flag.
+        let selected_name = self.dimstyle_selected.clone();
+        let Some(selected) = doc.dim_styles.get(&selected_name) else {
+            return;
+        };
+        if selected.xref_dependent || selected.name.contains('|') {
+            return;
+        }
+
         let text_style_handle = doc
             .text_styles
             .get(&self.ds_dimtxsty)
@@ -499,6 +522,9 @@ impl OpenCADStudio {
     /// Update a single string buffer field.
 
     pub(in crate::app) fn apply_ds_edit(&mut self, field: crate::app::DsField, val: String) {
+        if self.selected_dimstyle_is_read_only() {
+            return;
+        }
         use crate::app::DsField::*;
         match field {
             Dimdle => self.ds_dimdle = val,
@@ -570,6 +596,9 @@ impl OpenCADStudio {
     /// Toggle a boolean buffer field.
 
     pub(in crate::app) fn apply_ds_toggle(&mut self, field: crate::app::DsField) {
+        if self.selected_dimstyle_is_read_only() {
+            return;
+        }
         use crate::app::DsField::*;
         match field {
             Dimsd1 => self.ds_dimsd1 = !self.ds_dimsd1,
@@ -1260,6 +1289,9 @@ impl OpenCADStudio {
     }
 
     pub(super) fn on_ds_set_handle(&mut self, field: &'static str, value: String) -> Task<Message> {
+        if self.selected_dimstyle_is_read_only() {
+            return Task::none();
+        }
         let i = self.active_tab;
         let name = self.dimstyle_selected.clone();
         let is_lt = matches!(
@@ -1358,4 +1390,84 @@ mod ds_set_handle_tests {
             "picking the first arrowhead must not touch the second"
         );
     }
+
+    #[test]
+    fn xref_dimstyle_is_read_only_and_rejects_direct_edits() {
+        let mut app = app_with_arrow_blocks();
+        let i = app.active_tab;
+        let name = app.dimstyle_selected.clone();
+        let before = app.tabs[i]
+            .scene
+            .document
+            .dim_styles
+            .get(&name)
+            .unwrap()
+            .dimdle;
+        app.tabs[i]
+            .scene
+            .document
+            .dim_styles
+            .get_mut(&name)
+            .unwrap()
+            .xref_dependent = true;
+        assert!(app.selected_dimstyle_is_read_only());
+
+        app.ds_dimdle = "123".to_string();
+        app.apply_dimstyle_bufs(i);
+        let _ = app.on_ds_set_handle("dimblk1", "ARROW_A".to_string());
+
+        assert_eq!(
+            app.tabs[i]
+                .scene
+                .document
+                .dim_styles
+                .get(&name)
+                .unwrap()
+                .dimdle,
+            before
+        );
+        assert_eq!(
+            app.tabs[i]
+                .scene
+                .document
+                .dim_styles
+                .get(&name)
+                .unwrap()
+                .dimblk1,
+            codec::types::Handle::NULL
+        );
+    }
+
+    #[test]
+    fn merged_xref_dimstyle_name_is_read_only() {
+        let mut app = app_with_arrow_blocks();
+        let i = app.active_tab;
+        let old_name = app.dimstyle_selected.clone();
+        let mut style = app.tabs[i]
+            .scene
+            .document
+            .dim_styles
+            .get(&old_name)
+            .unwrap()
+            .clone();
+        let before = style.dimdle;
+        app.tabs[i].scene.document.dim_styles.remove(&old_name);
+        style.name = "ARCH|Imported".to_string();
+        app.tabs[i].scene.document.dim_styles.add_or_replace(style);
+        app.dimstyle_selected = "ARCH|Imported".to_string();
+
+        assert!(app.selected_dimstyle_is_read_only());
+        app.ds_dimdle = "456".to_string();
+        app.apply_dimstyle_bufs(i);
+        assert_ne!(
+            app.tabs[i]
+                .scene
+                .document
+                .dim_styles
+                .get("ARCH|Imported")
+                .unwrap()
+                .dimdle,
+            before
+        );
+    }
 }

src/app/view/modal.rs

@@ -1477,7 +1477,8 @@ impl OpenCADStudio {
                     }
                 };
                 let ds_sel = doc.dim_styles.get(&self.dimstyle_selected);
-                let read_only = false;
+                let read_only =
+                    ds_sel.is_none_or(|style| style.xref_dependent || style.name.contains('|'));
                 let in_use = doc.entities().any(|entity| {
                     matches!(entity, codec::EntityType::Dimension(dimension)
                     if dimension.base().style_name.eq_ignore_ascii_case(&self.dimstyle_selected))