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/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;