feat(view): DVIEW twists the view about its line of sight

DVIEW (alias DV) offers TWist and Undo. TWist rolls the active view
or viewport camera to the typed angle; Undo steps back through the
twists made in the session. The new alias reaches existing profiles
through the alias migration table.

Refs #638

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

src/app/alias.rs

@@ -80,7 +80,7 @@ const WEB_ALIAS_KEY: &str = "opencadstudio.aliases";
 /// migrated forward (see `introduced_at` / `migrate_aliases`). Version 1 shipped
 /// the pre-REDRAW table; version 2 introduced the REDRAW-family aliases; version 3
 /// introduced HB (HATCHTOBACK); version 4 introduced ER (EXTERNALREFERENCES).
-const DEFAULT_ALIASES_VERSION: u32 = 6;
+const DEFAULT_ALIASES_VERSION: u32 = 7;
 
 #[cfg(target_arch = "wasm32")]
 const WEB_ALIAS_VERSION_KEY: &str = "opencadstudio.aliases.version";
@@ -101,6 +101,7 @@ fn introduced_at(version: u32) -> &'static [(&'static str, &'static str)] {
         4 => &[("ER", "EXTERNALREFERENCES")],
         5 => &[("-ATT", "-ATTDEF")],
         6 => &[("VV", "QLAYER")],
+        7 => &[("DV", "DVIEW")],
         _ => &[],
     }
 }

src/app/command_driver/mod.rs

@@ -882,6 +882,9 @@ impl OpenCADStudio {
             CmdResult::ZoomToWindow { p1, p2 } => {
                 self.handle_zoom_to_window(p1, p2);
             }
+            CmdResult::TwistView(twist) => {
+                self.handle_twist_view(twist);
+            }
             CmdResult::Measurement(msg) => {
                 self.handle_measurement(msg);
             }

src/app/command_driver/viewport.rs

@@ -447,6 +447,26 @@ impl OpenCADStudio {
             .push_output(crate::t!("Zoom Window").as_ref());
     }
 
+    /// Turn the active view about its line of sight so the drawing shows
+    /// `twist` radians counter-clockwise from its untwisted orientation.
+    pub(in crate::app) fn handle_twist_view(&mut self, twist: f64) {
+        let i = self.active_tab;
+        self.tabs[i].scene.remember_current_view();
+        let set = |camera: &mut crate::scene::view::camera::Camera| {
+            // The drawing turns one way when the camera rolls the other.
+            camera.roll_by(-twist as f32 - camera.roll());
+        };
+        if self.tabs[i].scene.active_viewport.is_some() {
+            self.tabs[i].scene.mutate_active_viewport_camera(set);
+        } else {
+            set(&mut self.tabs[i].scene.camera.borrow_mut());
+        }
+        self.tabs[i].scene.camera_generation += 1;
+        if let Some(prompt) = self.tabs[i].active_cmd.as_ref().map(|c| c.prompt()) {
+            self.command_line.push_info(&prompt);
+        }
+    }
+
     pub(super) fn handle_set_plot_window(&mut self, p1: glam::DVec3, p2: glam::DVec3) {
         let i = self.active_tab;
         let layout_name = self.tabs[i].scene.current_layout.clone();

src/app/commands/dim.rs

@@ -935,6 +935,21 @@ impl OpenCADStudio {
                 self.tabs[i].active_cmd = Some(Box::new(cmd));
             }
 
+            "DVIEW" => {
+                use crate::modules::view::dview::DviewCommand;
+                let twist = {
+                    let scene = &self.tabs[i].scene;
+                    let roll = match scene.active_viewport {
+                        Some(_) => scene.navigation_camera().roll(),
+                        None => scene.camera.borrow().roll(),
+                    };
+                    -(roll as f64)
+                };
+                let cmd = DviewCommand::new(twist.rem_euclid(std::f64::consts::TAU));
+                self.command_line.push_info(&cmd.prompt());
+                self.tabs[i].active_cmd = Some(Box::new(cmd));
+            }
+
             "ZOOM" | "ZOOM WINDOW" | "ZOOM W" | "ZW" => {
                 use crate::modules::view::zoom_window::ZoomWindowCommand;
                 let new_cmd = ZoomWindowCommand::new();