Joints: gears, rack and pinion, and screws (#1524)

Motion links can carry a coupling (gear pair, rack and pinion, screw) whose ratio follows radii, picked round faces or pitch. Design format 23.

Co-authored-by: SychPL <SychPL@users.noreply.github.com>
Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

crates/ui-egui/src/dialogs_assembly.rs

@@ -1,5 +1,5 @@
 //! Assembly dialogs: New Component, Joint, As-built Joint, Joint Origin, Rigid Group, Drive
-//! Joints, Motion Link and Interference. Joint origins are picked by hovering geometry: a face
+//! Joints, Motion Link, Gear, Rack and Pinion, Screw (`dialogs_coupling`) and Interference. Joint origins are picked by hovering geometry: a face
 //! snaps to its centre (or a round face to the centre of its nearer end), an edge to its middle
 //! (a round edge to its centre), a vertex to itself; the snap shows as a glyph with its z axis
 //! before the click. Joints and drives preview on the placed (world) model: the moving
@@ -27,8 +27,19 @@ const TYPE_LABELS: [&str; 7] = ["Rigid", "Revolute", "Slider", "Cylindrical", "P
 /// What a joint origin input accepts (snaps on faces, edges and vertices).
 const SNAPS: u16 = FACES | EDGES | VERTICES;
 /// Commands whose effect is where occurrences sit (previewed on the placed model).
-const MOVES: [&str; 8] =
-    ["joint.create", "joint.as_built", "joint.drive", "joint.edit", "joint.limits", "joint.rigid_group", "parts.insert", "parts.fastener"];
+const MOVES: [&str; 11] = [
+    "joint.create",
+    "joint.as_built",
+    "joint.drive",
+    "joint.edit",
+    "joint.limits",
+    "joint.rigid_group",
+    "joint.gear",
+    "joint.rack_pinion",
+    "joint.screw",
+    "parts.insert",
+    "parts.fastener",
+];
 
 #[derive(Clone, Debug)]
 pub enum Asm {
@@ -56,6 +67,7 @@ pub enum Asm {
         ratio: String,
         offset: String,
     },
+    Coupling(Box<crate::dialogs_coupling::CouplingForm>),
     Interference {
         result: Option<Value>,
         overlaps: Vec<Mesh>,
@@ -128,12 +140,17 @@ impl Asm {
             Asm::RigidGroup => "RIGID GROUP",
             Asm::Drive { .. } => "DRIVE JOINTS",
             Asm::MotionLink { .. } => "MOTION LINK",
+            Asm::Coupling(f) => match f.command {
+                "joint.gear" => "GEAR",
+                "joint.rack_pinion" => "RACK AND PINION",
+                _ => "SCREW",
+            },
             Asm::Interference { .. } => "INTERFERENCE",
         }
     }
 
     pub fn previews(&self) -> bool {
-        matches!(self, Asm::Joint(_) | Asm::Drive { .. } | Asm::RigidGroup)
+        matches!(self, Asm::Joint(_) | Asm::Drive { .. } | Asm::RigidGroup | Asm::Coupling(_))
     }
 }
 
@@ -166,6 +183,7 @@ pub fn start(app: &SolveApp, id: &str) -> Option<(Kind, Vec<SelInput>)> {
             let b = usize::from(movable(s).len() > 1);
             (Asm::MotionLink { a: 0, b, ia: 0, ib: 0, ratio: "1".into(), offset: "0".into() }, vec![])
         }
+        "joint.gear" | "joint.rack_pinion" | "joint.screw" => crate::dialogs_coupling::start(app, id)?,
         "inspect.interference" => {
             (Asm::Interference { result: None, overlaps: Vec::new(), of: Vec::new() }, vec![SelInput::new("Bodies (all if none)", BODIES, true)])
         }
@@ -657,6 +675,7 @@ pub fn rows(app: &mut SolveApp, ui: &mut egui::Ui, k: &mut Asm, inputs: &mut [Se
             enter |= field(ui, offset);
             ui.end_row();
         }
+        Asm::Coupling(f) => enter |= crate::dialogs_coupling::rows(app, ui, f, inputs),
         Asm::Interference { result, overlaps, of } => {
             let picked: Vec<Sel> = inputs.first().map(|i| i.items.clone()).unwrap_or_default();
             row_label(ui, "");
@@ -883,6 +902,7 @@ pub fn commands(app: &SolveApp, k: &Asm, inputs: &[SelInput]) -> Result<Vec<(Str
             let ratio = eval(ratio, ValueKind::Unitless)?;
             cmd("joint.motion_link", json!({"a": ja.id, "b": jb.id, "ia": ia, "ib": ib, "ratio": ratio, "offset": offset.trim()}))
         }
+        Asm::Coupling(f) => return crate::dialogs_coupling::commands(app, f, inputs),
         // The check runs from its Compute button; OK only closes.
         Asm::Interference { .. } => Vec::new(),
     })
@@ -890,6 +910,9 @@ pub fn commands(app: &SolveApp, k: &Asm, inputs: &[SelInput]) -> Result<Vec<(Str
 
 /// The preview's commands: OK's, with the joint's values playing its motion while animating.
 pub fn animate(app: &SolveApp, k: &Asm, cmds: &mut Vec<(String, Value)>) {
+    if let Asm::Coupling(f) = k {
+        crate::dialogs_coupling::animate(&app.session, f, cmds);
+    }
     let Asm::Joint(f) = k else { return };
     if !f.animate {
         return;