feat(annotative): add/remove drawing annotation scales

The drawing's annotation-scale list (ACAD_SCALELIST) is now editable, so the
set of scales offered by the status-bar scale pill can be grown or trimmed:

- Scene::add_scale / remove_scale create or drop a Scale object and its
  SCALELIST dictionary entry (creating the SCALELIST dictionary, and
  registering it in the root, for drawings that carry none).
- SCALELISTEDIT gains ADD <ratio> / DELETE <name> alongside the existing
  listing (e.g. `SCALELISTEDIT ADD 1:50`).
- The scale popup (model space) grows a delete affordance on each non-active
  scale and a "+ Add scale..." row that primes the command line. The current
  annotation scale is protected from deletion.

Co-Authored-By: Claude Opus 4.8 <[email protected]>

src/app/commands/display.rs

@@ -704,19 +704,79 @@ impl OpenCADStudio {
                 }
             }
 
-            // SCALELISTEDIT — list the drawing's annotation scales.
+            // SCALELISTEDIT — list / add / delete the drawing's annotation scales.
+            //   SCALELISTEDIT              list
+            //   SCALELISTEDIT ADD 1:50     add (name is a paper:drawing ratio)
+            //   SCALELISTEDIT DELETE 1:50  remove (not the current scale)
             cmd if cmd == "SCALELISTEDIT" || cmd.starts_with("SCALELISTEDIT ") => {
-                let names: Vec<String> = self.tabs[i]
-                    .scene
-                    .scale_list()
-                    .into_iter()
-                    .map(|(n, _, _)| n)
-                    .collect();
-                if names.is_empty() {
-                    self.command_line.push_info("No annotation scales defined.");
-                } else {
-                    self.command_line
-                        .push_output(&format!("Annotation scales: {}", names.join(", ")));
+                let rest = cmd.trim_start_matches("SCALELISTEDIT").trim();
+                let mut parts = rest.splitn(2, char::is_whitespace);
+                let sub = parts.next().unwrap_or("").to_uppercase();
+                let arg = parts.next().unwrap_or("").trim();
+                match sub.as_str() {
+                    "ADD" => match arg.split_once(':') {
+                        Some((p, d)) => match (p.trim().parse::<f64>(), d.trim().parse::<f64>()) {
+                            (Ok(paper), Ok(drawing)) if paper > 0.0 && drawing > 0.0 => {
+                                self.push_undo_snapshot(i, "SCALELISTEDIT");
+                                if self.tabs[i].scene.add_scale(arg, paper, drawing) {
+                                    self.tabs[i].dirty = true;
+                                    self.command_line
+                                        .push_output(&format!("Added annotation scale {arg}."));
+                                } else {
+                                    self.command_line
+                                        .push_info(&format!("Scale {arg} already exists."));
+                                }
+                            }
+                            _ => self
+                                .command_line
+                                .push_error("SCALELISTEDIT ADD: use a ratio like 1:50."),
+                        },
+                        None => self
+                            .command_line
+                            .push_error("SCALELISTEDIT ADD: use a ratio like 1:50."),
+                    },
+                    "DELETE" | "REMOVE" => {
+                        let current = self.tabs[i]
+                            .scene
+                            .document
+                            .header
+                            .current_annotation_scale
+                            .clone();
+                        if arg.is_empty() {
+                            self.command_line.push_info("Usage: SCALELISTEDIT DELETE <name>");
+                        } else if arg.eq_ignore_ascii_case(&current) {
+                            self.command_line.push_error(&format!(
+                                "Cannot delete the current annotation scale ({arg})."
+                            ));
+                        } else {
+                            self.push_undo_snapshot(i, "SCALELISTEDIT");
+                            if self.tabs[i].scene.remove_scale(arg) {
+                                self.tabs[i].dirty = true;
+                                self.command_line
+                                    .push_output(&format!("Removed annotation scale {arg}."));
+                            } else {
+                                self.command_line
+                                    .push_info(&format!("No annotation scale named {arg}."));
+                            }
+                        }
+                    }
+                    "" => {
+                        let names: Vec<String> = self.tabs[i]
+                            .scene
+                            .scale_list()
+                            .into_iter()
+                            .map(|(n, _, _)| n)
+                            .collect();
+                        if names.is_empty() {
+                            self.command_line.push_info("No annotation scales defined.");
+                        } else {
+                            self.command_line
+                                .push_output(&format!("Annotation scales: {}", names.join(", ")));
+                        }
+                    }
+                    _ => self
+                        .command_line
+                        .push_info("Usage: SCALELISTEDIT [ADD 1:50 | DELETE 1:50]"),
                 }
             }
 

src/app/mod.rs

@@ -1455,6 +1455,10 @@ pub enum Message {
     ToggleScalePopup,
     /// Close the scale picker popup.
     CloseScalePopup,
+    /// Delete a named annotation scale from the drawing's ACAD_SCALELIST.
+    ScaleListDelete(String),
+    /// Prime the command line to add a new annotation scale.
+    ScaleListAddPrompt,
     /// Toggle the leftmost hamburger's Model/layout list dropdown.
     ToggleLayoutList,
     /// Close the Model/layout list dropdown.

src/app/update/mod.rs

@@ -1647,6 +1647,31 @@ impl OpenCADStudio {
                 self.scale_popup_open = false;
                 Task::none()
             }
+            Message::ScaleListDelete(name) => {
+                let i = self.active_tab;
+                let current = self.tabs[i]
+                    .scene
+                    .document
+                    .header
+                    .current_annotation_scale
+                    .clone();
+                // Keep the popup open so several can be removed in a row; never
+                // remove the current annotation scale out from under the drawing.
+                if !name.eq_ignore_ascii_case(&current) {
+                    self.push_undo_snapshot(i, "SCALELISTEDIT");
+                    if self.tabs[i].scene.remove_scale(&name) {
+                        self.tabs[i].dirty = true;
+                    }
+                }
+                Task::none()
+            }
+            Message::ScaleListAddPrompt => {
+                // Close the popup and prime the command line; the user types the
+                // ratio (e.g. 1:50) and commits it via SCALELISTEDIT ADD.
+                self.scale_popup_open = false;
+                self.command_line.input = "SCALELISTEDIT ADD ".to_string();
+                Task::none()
+            }
             Message::ToggleLayoutList => {
                 self.layout_list_open ^= true;
                 Task::none()