Rounded Rectangle sketch tool (#891) (#948)

* Rounded Rectangle sketch tool (#891)

A new SKETCH > CREATE command, sketch.rectangle.rounded, in the Rectangle
family: two opposite corners and a corner radius make a 2-point rectangle
whose four corners are filleted alike, as one undo step. The radius is one
parameter (one radius dimension, the other arcs equal to it), so changing it
changes all four corners. While drawing, Width, Height and Radius boxes take
typed values; typed width and height dimension the overall size between
opposite sides. Without a typed radius the corners get a fifth of the shorter
side.

Fixes #891

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

* Rounded Rectangle in the Simplified Chinese catalog

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>

crates/ui-egui/src/tools.rs

@@ -53,6 +53,7 @@ impl Tool {
             "sketch.line" => ("sketch.line", Kind::Draw(0)),
             "sketch.rectangle.two_point" => ("sketch.rectangle.two_point", Kind::Draw(2)),
             "sketch.rectangle.center" => ("sketch.rectangle.center", Kind::Draw(2)),
+            "sketch.rectangle.rounded" => ("sketch.rectangle.rounded", Kind::Draw(2)),
             "sketch.rectangle.three_point" => ("sketch.rectangle.three_point", Kind::Draw(3)),
             "sketch.circle.center" => ("sketch.circle.center", Kind::Draw(2)),
             "sketch.circle.two_point" => ("sketch.circle.two_point", Kind::Draw(2)),
@@ -98,6 +99,7 @@ pub fn hint(id: &str) -> String {
         "sketch.line" => "Line: click points; right-click or Esc to finish".into(),
         "sketch.rectangle.two_point" => "Rectangle: click two opposite corners".into(),
         "sketch.rectangle.center" => "Center rectangle: click the centre, then a corner".into(),
+        "sketch.rectangle.rounded" => "Rounded rectangle: click two opposite corners (Tab to the radius box to type the corner radius)".into(),
         "sketch.rectangle.three_point" => "3-point rectangle: click two points of one edge, then the width".into(),
         "sketch.circle.center" => "Circle: click the centre, then a point on the circle".into(),
         "sketch.arc.three_point" => "Arc: click start, end, then a point on the arc".into(),
@@ -347,6 +349,9 @@ fn run_shape(app: &mut SolveApp, t: &Tool) -> Result<Vec<String>, String> {
     let params = match t.cmd {
         "sketch.rectangle.two_point" => json!({"p0": xy(&p[0]), "p1": xy(&p[1])}),
         "sketch.rectangle.center" => json!({"center": xy(&p[0]), "corner": xy(&p[1])}),
+        "sketch.rectangle.rounded" => {
+            json!({"p0": xy(&p[0]), "p1": xy(&p[1]), "radius": crate::sketch_dims::rounded_radius_value(app, t, p[0].0, p[1].0)})
+        }
         "sketch.rectangle.three_point" => json!({"p0": xy(&p[0]), "p1": xy(&p[1]), "p2": xy(&p[2])}),
         "sketch.circle.center" => json!({"center": arg(&p[0]), "radius": d(0, 1)}),
         "sketch.circle.two_point" => json!({"p0": xy(&p[0]), "p1": xy(&p[1])}),
@@ -729,6 +734,11 @@ pub fn preview(app: &SolveApp, t: &Tool, painter: &egui::Painter, proj: &Proj) {
             line(h, c);
             line(c, *a);
         }
+        ("sketch.rectangle.rounded", [a]) => {
+            let r = crate::sketch_dims::rounded_radius(app, t, *a, h);
+            let outline: Vec<_> = rounded_outline(*a, h, r).into_iter().map(|q| ss.plane.to_world(q)).collect();
+            paint_sketch_path(&outline, crate::sketch_palette::mode(app), painter, proj, stroke);
+        }
         ("sketch.rectangle.center", [c]) => {
             let d = h - *c;
             let k =
@@ -745,3 +755,28 @@ pub fn preview(app: &SolveApp, t: &Tool, painter: &egui::Painter, proj: &Proj) {
         _ => {}
     }
 }
+
+/// The closed outline of the rectangle with corners `a`, `b` and corner radius `r` (clamped to
+/// fit), as points for a preview: counter-clockwise, arcs sampled, first point repeated last.
+pub(crate) fn rounded_outline(a: Vec2, b: Vec2, r: f64) -> Vec<Vec2> {
+    let (lo, hi) = (Vec2::new(a.x.min(b.x), a.y.min(b.y)), Vec2::new(a.x.max(b.x), a.y.max(b.y)));
+    let r = if r.is_finite() { r.clamp(0.0, 0.5 * (hi.x - lo.x).min(hi.y - lo.y)) } else { 0.0 };
+    let q = std::f64::consts::FRAC_PI_2;
+    // Corner centres and the angle each arc starts at, CCW from the bottom-right corner.
+    let corners = [
+        (Vec2::new(hi.x - r, lo.y + r), -q),
+        (Vec2::new(hi.x - r, hi.y - r), 0.0),
+        (Vec2::new(lo.x + r, hi.y - r), q),
+        (Vec2::new(lo.x + r, lo.y + r), 2.0 * q),
+    ];
+    let mut pts = Vec::with_capacity(4 * 9 + 1);
+    for (c, a0) in corners {
+        for i in 0..=8 {
+            pts.push(c + Vec2::from_angle(a0 + q * f64::from(i) / 8.0) * r);
+        }
+    }
+    if let Some(first) = pts.first().copied() {
+        pts.push(first);
+    }
+    pts
+}