Add a Drafting page for the rotation angle and the polar increment

Two drafting preferences had no proper home. The Drafting Settings dialog
displays the drafting rotation and offers only a Reset button — there was no
way to type an angle short of `SETVAR SNAPANG`. The polar tracking increment
existed in exactly one place: a pop-up hanging off the status-bar pill.

The rotation is a text field over an edit buffer rather than the value
itself, so clearing it to retype does not snap the crosshair to zero on the
way through; the buffer is reseeded whenever the value is restored from
behind it. Angles render without a trailing `.0`, matching how the polar
pop-up has always shown them — same kind of number, same reader.

Snap modes, grid spacing and object snap stay in Drafting Settings, where
they belong; the page links to it.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

src/app/mod.rs

@@ -517,6 +517,9 @@ pub(super) struct OpenCADStudio {
     crosshair_color: Option<[u8; 3]>,
     /// Editable Options buffer for the crosshair colour.
     crosshair_color_input: String,
+    /// Edit buffer for the SNAPANG field on the Options Drafting page. Kept
+    /// separate from `snap_angle_deg` so a half-typed angle is not parsed.
+    snap_angle_input: String,
     /// Model-space lineweight preview scale, in percent (25..=200).
     lineweight_display_scale: i32,
     /// Isometric drafting state and active axis pair.
@@ -2029,6 +2032,10 @@ pub enum Message {
     QdimSnapPriorityChanged(u8),
     /// Change which annotative objects pick up a new scale (ANNOAUTOSCALE).
     AnnoAutoScaleChanged(i8),
+    /// Edit the drafting rotation field; parsed when it holds a valid angle (SNAPANG).
+    SnapAngleInputChanged(String),
+    /// Change the polar tracking increment in degrees.
+    PolarIncrementChanged(f32),
     /// Restore Model Space display/canvas appearance to defaults.
     RestoreModelSpaceDisplayDefaults,
     /// Restore Selection visual effect settings to defaults.
@@ -3429,6 +3436,7 @@ impl OpenCADStudio {
             cursor_type: settings::CursorType::Crosshair,
             crosshair_color: None,
             crosshair_color_input: String::new(),
+            snap_angle_input: "0".to_string(),
             lineweight_display_scale: 100,
             isometric_drafting: false,
             iso_plane: settings::IsoPlane::Left,

src/app/settings.rs

@@ -145,6 +145,18 @@ pub(crate) fn snaps_from_osmode(osmode: i32) -> (Vec<SnapType>, bool) {
     (modes, osmode & OSMODE_SUPPRESS == 0)
 }
 
+/// Render a drafting angle without a trailing `.0`, so `22.5` but `30`.
+///
+/// The polar pop-up formats its presets the same way; both are showing the
+/// same kind of number to the same person.
+pub fn format_snap_angle(deg: f32) -> String {
+    if (deg - deg.round()).abs() < 1e-4 {
+        format!("{}", deg.round() as i32)
+    } else {
+        format!("{deg}")
+    }
+}
+
 /// GRIPOBJLIMIT default: past this many selected objects, no grips are drawn.
 pub const DEFAULT_GRIP_OBJECT_LIMIT: i32 = 100;
 

src/app/update/file.rs

@@ -452,6 +452,9 @@ impl OpenCADStudio {
         } else {
             0.0
         };
+        // The Options field edits a buffer rather than the value, so it has to
+        // be reseeded whenever the value is restored from behind it.
+        self.snap_angle_input = crate::app::settings::format_snap_angle(self.snap_angle_deg);
         // Ortho + running OSNAP are per-drawing (adopted from the header on
         // open / tab switch), not app-global, so they are not applied here.
         self.snapper.otrack_enabled = s.otrack;

src/app/update/mod.rs

@@ -6266,6 +6266,27 @@ impl OpenCADStudio {
                 Task::none()
             }
 
+            // Typed into freely; only committed when it parses, so clearing
+            // the field to retype does not snap the crosshair back to zero.
+            Message::SnapAngleInputChanged(value) => {
+                self.snap_angle_input = value;
+                if let Ok(angle) = self.snap_angle_input.trim().parse::<f32>() {
+                    if angle.is_finite() {
+                        self.snap_angle_deg = angle.rem_euclid(360.0);
+                        self.persist_settings_if_changed();
+                    }
+                }
+                Task::none()
+            }
+
+            Message::PolarIncrementChanged(deg) => {
+                if deg.is_finite() && deg > 0.0 {
+                    self.polar_increment_deg = deg;
+                    self.persist_settings_if_changed();
+                }
+                Task::none()
+            }
+
             Message::PickDragRectToggled(rectangle) => {
                 self.pick_drag_rect = rectangle;
                 self.persist_settings_if_changed();

src/app/view/modal.rs

@@ -204,7 +204,9 @@ impl OpenCADStudio {
                             dimension_continue_mode: self.dimension_continue_mode,
                             qdim_snap_priority: self.quick_dimension_snap_priority,
                             annotation_auto_scale: self.annotation_auto_scale,
+                            polar_increment_deg: self.polar_increment_deg,
                         },
+                        &self.snap_angle_input,
                         self.double_click_block_refedit,
                         self.double_click_block_attedit,
                         self.cursor_type,