Equal: ask for the second object again after a refused pick, name the kind it needs

A second object of the wrong kind (a circle after a line, a line after a
circle) or a pair that already carries Equal now reports and asks for the
second object again instead of ending the command. The mismatch message
names what the first object asks for — `Select a line segment, polyline
segment, text, MText, major or minor axis of ellipse or elliptical arc.`
after a length object, `Select a circle or arc.` after a radius object —
and the same-pick message carries the reference's double space.

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

src/app/command_driver.rs

@@ -3357,8 +3357,13 @@ impl OpenCADStudio {
                         || equal_size_follower(&self.tabs[i].scene.document, first, other)
                             .is_none()
                     {
-                        self.command_line
-                            .push_error(EqualConstraintCommand::INVALID_OBJECT);
+                        // The reference names the kind the first object
+                        // asks for.
+                        let message = match equal_size(&self.tabs[i].scene.document, first) {
+                            Some(EqualSize::Radius(_)) => EqualConstraintCommand::INVALID_RADIUS_OBJECT,
+                            _ => EqualConstraintCommand::INVALID_LENGTH_OBJECT,
+                        };
+                        self.command_line.push_error(message);
                         continue;
                     }
                     let exists = self.tabs[i]
@@ -3378,7 +3383,10 @@ impl OpenCADStudio {
                     }
                     followers.push(other);
                 }
-                if multiple && !finishing {
+                // A refused second object is asked for again, as in the
+                // reference; Multiple keeps asking anyway.
+                let keep = (multiple && !finishing) || (!multiple && followers.is_empty());
+                if keep {
                     if let Some(prompt) =
                         self.tabs[i].active_cmd.as_ref().map(|command| command.prompt())
                     {
@@ -3601,7 +3609,7 @@ impl OpenCADStudio {
                                     ("No valid constraint point found.", Some(first))
                                 } else {
                                     (
-                                        "The object or point is already selected. Select a different object or constraint point.",
+                                        "The object or point is already selected.  Select a different object or constraint point.",
                                         Some(first),
                                     )
                                 };

src/modules/parametric/equal.rs

@@ -31,8 +31,12 @@ impl EqualConstraintCommand {
     pub const NO_OBJECT: &'static str = "No object found.";
     pub const INVALID_OBJECT: &'static str =
         "Invalid selection for Equal. Select a line, polyline segment, circle or arc.";
+    pub const INVALID_LENGTH_OBJECT: &'static str =
+        "Invalid selection for Equal. Select a line segment, polyline segment, text, MText, major or minor axis of ellipse or elliptical arc.";
+    pub const INVALID_RADIUS_OBJECT: &'static str =
+        "Invalid selection for Equal. Select a circle or arc.";
     pub const SAME_OBJECT: &'static str =
-        "The object or point is already selected. Select a different object or constraint point.";
+        "The object or point is already selected.  Select a different object or constraint point.";
 
     pub fn new() -> Self {
         Self {

src/modules/parametric/horizontal.rs

@@ -200,7 +200,7 @@ impl HorizontalConstraintCommand {
         if first.handle == second.handle && (first.point - second.point).length() <= 1.0e-9 {
             self.step = Step::SecondPoint(first);
             return CmdResult::ReportError(
-                "The object or point is already selected. Select a different object or constraint point."
+                "The object or point is already selected.  Select a different object or constraint point."
                     .to_string(),
             );
         }