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();

src/command.rs

@@ -1935,6 +1935,9 @@ pub enum CmdResult {
     PasteClipboard {
         base_pt: DVec3,
     },
+    /// Set the view's twist about its line of sight (radians,
+    /// counter-clockwise); the command stays active.
+    TwistView(f64),
     /// Zoom the model-space camera to fit the given corner points; end command.
     ZoomToWindow {
         p1: DVec3,

src/locale_catalog.rs

@@ -3838,6 +3838,9 @@ pub(super) fn message_attribute(source: &str) -> Option<(&'static str, &'static
         "ZOOM  [Window / Extents / Extents All / All / In / Out / Scale]:" => Some(("view", "zoom-window-extents-extents-all-all-in-out-sca")),
         "ZOOM  scale factor (e.g. 2 or 0.5):" => Some(("annotate", "zoom-scale-factor-e-g-2-or-0-5")),
         "ZOOM WINDOW  Specify first corner:" => Some(("view", "zoom-window-specify-first-corner")),
+        "DVIEW  Enter option [TWist/Undo]:" => Some(("view", "dview-enter-option-twist-undo")),
+        "DVIEW  Specify view twist angle <{current}>:" => Some(("view", "dview-specify-view-twist-angle")),
+        "TWist" => Some(("view", "twist-option")),
         "ZOOM WINDOW  Specify opposite corner:" => Some(("view", "zoom-window-specify-opposite-corner")),
         "Zero" => Some(("properties", "zero")),
         "Zero suppress (DIMALTZ)" => Some(("common", "zero-suppress-dimaltz")),

src/modules/view/dview.rs

@@ -0,0 +1,89 @@
+// DVIEW command — turn the view about its line of sight (TWist).
+
+use crate::t;
+use glam::DVec3;
+
+use crate::command::{CadCommand, CmdOption, CmdResult};
+
+pub struct DviewCommand {
+    /// The view's twist when the command started or last changed, radians.
+    current: f64,
+    /// Earlier twists, for Undo.
+    history: Vec<f64>,
+    twist_prompt: bool,
+}
+
+impl DviewCommand {
+    /// `current` is the view's present twist, counter-clockwise, in radians.
+    pub fn new(current: f64) -> Self {
+        Self {
+            current,
+            history: Vec::new(),
+            twist_prompt: false,
+        }
+    }
+}
+
+impl CadCommand for DviewCommand {
+    fn name(&self) -> &'static str {
+        "DVIEW"
+    }
+
+    fn prompt(&self) -> String {
+        if self.twist_prompt {
+            let current = crate::entities::common::format_angle(self.current);
+            crate::tf!("DVIEW  Specify view twist angle <{current}>:").into_owned()
+        } else {
+            t!("DVIEW  Enter option [TWist/Undo]:").into_owned()
+        }
+    }
+
+    fn options(&self) -> Vec<CmdOption> {
+        if self.twist_prompt {
+            return Vec::new();
+        }
+        vec![CmdOption::new("TWist", "TW"), CmdOption::new("Undo", "U")]
+    }
+
+    fn wants_text_input(&self) -> bool {
+        true
+    }
+
+    fn on_text_input(&mut self, text: &str) -> Option<CmdResult> {
+        let text = text.trim();
+        if self.twist_prompt {
+            let twist = crate::entities::common::parse_angle(&text.replace(',', "."))?;
+            self.twist_prompt = false;
+            self.history.push(self.current);
+            self.current = twist;
+            return Some(CmdResult::TwistView(twist));
+        }
+        match text.trim_start_matches('_').to_ascii_uppercase().as_str() {
+            "TW" | "TWIST" => {
+                self.twist_prompt = true;
+                Some(CmdResult::NeedPoint)
+            }
+            "U" | "UNDO" => {
+                let previous = self.history.pop()?;
+                self.current = previous;
+                Some(CmdResult::TwistView(previous))
+            }
+            _ => None,
+        }
+    }
+
+    fn on_point(&mut self, _pt: DVec3) -> CmdResult {
+        CmdResult::NeedPoint
+    }
+
+    fn on_enter(&mut self) -> CmdResult {
+        if self.twist_prompt {
+            // Enter keeps the current twist and returns to the options.
+            self.twist_prompt = false;
+            return CmdResult::NeedPoint;
+        }
+        CmdResult::Cancel
+    }
+}
+
+inventory::submit!(crate::command::CommandRegistration { names: &["DVIEW"] });

src/modules/view/mod.rs

@@ -5,6 +5,7 @@ mod count_palette;
 mod file_tabs;
 mod graphic_attributes_palette;
 mod layout_tabs;
+pub mod dview;
 pub mod limits;
 mod orbit;
 mod ortho;