Linear dimensional constraints: point flow, dynamic dimension, driving parameter

DCLINEAR, DCHORIZONTAL, DCVERTICAL and DCALIGNED follow the reference flow:
`Specify first constraint point or [Object] <Object>:`, `Specify second
constraint point:`, `Specify dimension line location:`, then `Dimension
text = …` and `Enter value or name and value <d1=100>:`. Linear reads
horizontal or vertical from the dimension line location the way a linear
dimension does; Object takes a line's, an arc's or a polyline segment's
ends. A miss reports `No valid constraint point found.` / `No object
found.` and asks again; another object type reports `Invalid selection for
Linear. Select a line, polyline segment or arc.`.

Each constraint creates a drawing parameter (`d1`, `d2`, …, or the typed
`name=expression`), drives the constraint through it, and draws a dynamic
dimension in constraint gray whose text follows CONSTRAINTNAMEFORMAT
(`d1=100.0000`); the dimension is associated with the constrained objects
and its text is refreshed after every solve. A typed value other than the
measured one moves the second point while the first stays, and so does a
later parameter edit. Deleting the constraint removes its dimension and,
when nothing else reads it, its parameter.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

src/modules/annotate/aligned_dim.rs

@@ -67,26 +67,36 @@ impl AlignedDimensionCommand {
         let first = self.plane.to_local(first);
         let second = self.plane.to_local(second);
         let point = self.plane.to_local(point);
-        let mut dim = DimensionAligned::new(v3(first), v3(second));
-        // The placement point is stored so commit matches the preview.
-        dim.definition_point = v3(point);
-        dim.base.definition_point = v3(point);
-        let (d1, d2) = dim_line_endpoints(first, second, point);
-        dim.base.text_middle_point = v3((d1 + d2) * 0.5);
-        dim.base.insertion_point = dim.base.text_middle_point;
-        dim.base.actual_measurement = dim.measurement();
-        crate::entities::dimension::set_dimension_text_override(
-            &mut dim.base,
-            self.text_override.clone(),
-        );
+        let mut entity = aligned_dimension_entity(first, second, point, self.text_override.clone());
         // An explicit text angle overrides the default rotation.
-        if let Some(angle) = self.text_angle {
-            dim.base.text_rotation = angle;
+        if let (Some(angle), EntityType::Dimension(dimension)) = (self.text_angle, &mut entity) {
+            dimension.base_mut().text_rotation = angle;
         }
-        self.plane.place_entity(EntityType::Dimension(Dimension::Aligned(dim)))
+        self.plane.place_entity(entity)
     }
 }
 
+/// An aligned dimension between two points of the working plane, its
+/// dimension line through `point` — what DIMALIGNED places and what an
+/// aligned dimensional constraint draws.
+pub(crate) fn aligned_dimension_entity(
+    first: DVec3,
+    second: DVec3,
+    point: DVec3,
+    text_override: Option<String>,
+) -> EntityType {
+    let mut dim = DimensionAligned::new(v3(first), v3(second));
+    // The placement point is stored so commit matches the preview.
+    dim.definition_point = v3(point);
+    dim.base.definition_point = v3(point);
+    let (d1, d2) = dim_line_endpoints(first, second, point);
+    dim.base.text_middle_point = v3((d1 + d2) * 0.5);
+    dim.base.insertion_point = dim.base.text_middle_point;
+    dim.base.actual_measurement = dim.measurement();
+    crate::entities::dimension::set_dimension_text_override(&mut dim.base, text_override);
+    EntityType::Dimension(Dimension::Aligned(dim))
+}
+
 impl CadCommand for AlignedDimensionCommand {
     fn set_working_plane(&mut self, plane: WorkingPlane) {
         self.plane = plane;

src/modules/annotate/linear_dim.rs

@@ -15,7 +15,7 @@ use glam::DVec3;
 use crate::t;
 
 /// Select the measured axis from where the dimension line clears the points.
-fn measure_axis(first: DVec3, second: DVec3, def: DVec3) -> DVec3 {
+pub(crate) fn measure_axis(first: DVec3, second: DVec3, def: DVec3) -> DVec3 {
     let outside = |value: f64, a: f64, b: f64| {
         let (low, high) = if a <= b { (a, b) } else { (b, a) };
         (low - value).max(value - high).max(0.0)
@@ -113,26 +113,38 @@ impl LinearDimensionCommand {
         let first = self.plane.to_local(first);
         let second = self.plane.to_local(second);
         let point = self.plane.to_local(point);
-        let mut dim = DimensionLinear::new(v3(first), v3(second));
         let axis = self.axis_mode.axis(first, second, point);
-        dim.rotation = axis.y.atan2(axis.x);
-        dim.set_offset(dimension_line_offset(second, point, axis));
-        dim.base.definition_point = dim.definition_point;
-        dim.base.text_middle_point = v3(linear_text_pos(first, second, point, axis));
-        dim.base.insertion_point = dim.base.text_middle_point;
-        dim.base.actual_measurement = dim.measurement();
-        crate::entities::dimension::set_dimension_text_override(
-            &mut dim.base,
-            self.text_override.clone(),
-        );
+        let mut entity =
+            linear_dimension_entity(first, second, point, axis, self.text_override.clone());
         // An explicit text angle overrides the UCS-derived rotation.
-        if let Some(angle) = self.text_angle {
-            dim.base.text_rotation = angle;
+        if let (Some(angle), EntityType::Dimension(dimension)) = (self.text_angle, &mut entity) {
+            dimension.base_mut().text_rotation = angle;
         }
-        self.plane.place_entity(EntityType::Dimension(Dimension::Linear(dim)))
+        self.plane.place_entity(entity)
     }
 }
 
+/// A linear dimension between two points of the working plane, its
+/// dimension line through `point` along `axis` — what DIMLINEAR places and
+/// what a dynamic dimensional constraint draws.
+pub(crate) fn linear_dimension_entity(
+    first: DVec3,
+    second: DVec3,
+    point: DVec3,
+    axis: DVec3,
+    text_override: Option<String>,
+) -> EntityType {
+    let mut dim = DimensionLinear::new(v3(first), v3(second));
+    dim.rotation = axis.y.atan2(axis.x);
+    dim.set_offset(dimension_line_offset(second, point, axis));
+    dim.base.definition_point = dim.definition_point;
+    dim.base.text_middle_point = v3(linear_text_pos(first, second, point, axis));
+    dim.base.insertion_point = dim.base.text_middle_point;
+    dim.base.actual_measurement = dim.measurement();
+    crate::entities::dimension::set_dimension_text_override(&mut dim.base, text_override);
+    EntityType::Dimension(Dimension::Linear(dim))
+}
+
 impl CadCommand for LinearDimensionCommand {
     fn name(&self) -> &'static str {
         "DIMLINEAR"