Attach Underlay ribbon menu, DWF/DGN attach dialog, DGN true colours

- Insert > Reference: the PDF Attach button becomes an Attach Underlay menu
  (PDF / DWF / DGN); its face runs the last one chosen.
- DWFATTACH, DGNATTACH and ATTACH on a .dwf/.dwfx/.dgn open the Attach
  dialog for that kind: sheets or models with thumbnails (one chosen),
  placement, path type, file details with the sheet / model size, and for
  DGN the conversion units (sub units offer 1 / sub units per master as the
  scale).
- DGN V8 true colours come from the ExtendedColors record packed in the
  non-model attributes stream; the colour word's high part numbers them.
- A DGN model's extent includes each text's box (its length along the
  baseline and 1.5 x its height), as the reference sizes a model.
- DWFx text uses the family named in its embedded (deobfuscated) font.
- DWF contrast pivots at 0.73 once colours are turned over for a dark
  background.
- Hairline strokes are drawn solid one pixel wide, and underlay rasters are
  made at or below their size on screen so those lines stay unbroken.

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

src/modules/insert/mod.rs

@@ -53,7 +53,18 @@ impl CadModule for InsertModule {
                     title: "Reference",
                     tools: vec![
                         RibbonItem::LargeTool(xattach::tool()),
-                        RibbonItem::LargeTool(pdf_attach::tool()),
+                        // PDF, DWF or DGN; the face runs the last one chosen.
+                        RibbonItem::LargeDropdown {
+                            id: "UNDERLAY_ATTACH",
+                            label: "Attach Underlay",
+                            icon: pdf_attach::ICON,
+                            items: vec![
+                                ("PDFATTACH", "Attach PDF", pdf_attach::ICON),
+                                ("DWFATTACH", "Attach DWF", pdf_attach::ICON),
+                                ("DGNATTACH", "Attach DGN", pdf_attach::ICON),
+                            ],
+                            default: "PDFATTACH",
+                        },
                         RibbonItem::LargeTool(xclip::tool()),
                         RibbonItem::LargeTool(xadjust::tool()),
                         RibbonItem::LabeledTool(underlay_layers::tool()),

src/modules/insert/pdf_attach.rs

@@ -23,20 +23,11 @@ use glam::DVec3;
 
 use crate::command::{CadCommand, CmdOption, CmdResult, InputKind, WorkingPlane};
 use crate::scene::model::wire_model::WireModel;
-use crate::modules::{IconKind, ModuleEvent, ToolDef};
+use crate::modules::IconKind;
 
 pub const ICON: IconKind =
     IconKind::Svg(include_bytes!("../../../assets/icons/underlay_layers.svg"));
 
-pub fn tool() -> ToolDef {
-    ToolDef {
-        id: "PDFATTACH",
-        label: "Attach PDF",
-        icon: ICON,
-        event: ModuleEvent::Command("PDFATTACH".to_string()),
-    }
-}
-
 /// Units the Unit option offers: keyword, the name the prompt shows.
 const UNITS: [(&str, &str); 9] = [
     ("MM", "Millimeters"),
@@ -172,11 +163,6 @@ impl PdfAttachCommand {
         }
     }
 
-    /// PDFATTACH with a file already chosen: starts at the page prompt.
-    pub fn with_file(path: &str, insunits: i16) -> Self {
-        Self::with_kind_file(UnderlayType::Pdf, path, insunits)
-    }
-
     /// DWFATTACH / DGNATTACH / PDFATTACH with the file chosen: starts at the
     /// page, sheet or model prompt.
     pub fn with_kind_file(kind: UnderlayType, path: &str, insunits: i16) -> Self {
@@ -216,23 +202,34 @@ impl PdfAttachCommand {
         }
     }
 
-    /// The dialog's attach with the insertion point asked on screen: pages
-    /// chosen, the path to store, and any scale / rotation already given.
-    pub fn from_dialog(
+    /// The DWF / DGN (or PDF) Attach dialog: the sheet or model chosen and,
+    /// for DGN, whether sub units were chosen (their scale is then offered).
+    #[allow(clippy::too_many_arguments)]
+    pub fn from_kind_dialog(
+        kind: UnderlayType,
         read_path: &str,
         stored_path: &str,
         pages: &[String],
         scale: Option<f64>,
         rotation_deg: Option<f64>,
+        sub_units: bool,
         insunits: i16,
     ) -> Self {
-        let mut command = Self::with_file(read_path, insunits);
+        let mut command = Self::with_kind_file(kind, read_path, insunits);
         command.stored_path = Some(stored_path.to_string());
         if let Some((first, rest)) = pages.split_first() {
             command.page = first.clone();
             command.extra_pages = rest.to_vec();
         }
         command.rect = command.page_rect(&command.page);
+        if kind == UnderlayType::Dgn && sub_units {
+            let sub = crate::scene::model::underlay_vector::sheet(kind, read_path, &command.page)
+                .map(|s| s.sub_per_master)
+                .filter(|v| *v > 0.0)
+                .unwrap_or(1.0);
+            command.default_scale = 1.0 / sub;
+            command.scale = command.default_scale;
+        }
         command.preset_scale = scale;
         if let Some(s) = scale {
             command.scale = s;