Sketch Text (MTextCmd, sketch.edit_text): glyph outlines of the embedded Liberation Sans (SIL OFL 1.1, attributed) as lines and conics that close into extrudable profiles; editable text, height, position and angle

Co-Authored-By: Claude Opus 5.5 <[email protected]>
Claude-Session: https://claude.ai/code/session_01AS5Tn3xieewUSg3uxrMVdL

crates/sketch/src/curves.rs

@@ -34,7 +34,10 @@ pub fn conic_point(a: Vec2, apex: Vec2, b: Vec2, rho: f64, t: f64) -> Vec2 {
 }
 
 pub fn conic_polyline(a: Vec2, apex: Vec2, b: Vec2, rho: f64) -> Vec<Vec2> {
-    let n = SPAN_SAMPLES * 2;
+    // Samples by how far the curve bows from its chord (small text curves need few).
+    let chord = b - a;
+    let bow = chord.cross(apex - a).abs() / chord.len().max(1e-12);
+    let n = ((bow / 2e-3).sqrt().ceil() as usize).clamp(2, SPAN_SAMPLES * 2);
     (0..=n).map(|i| conic_point(a, apex, b, rho, i as f64 / n as f64)).collect()
 }
 

crates/sketch/src/lib.rs

@@ -15,6 +15,7 @@ mod model;
 mod profiles;
 mod shape;
 mod solver;
+mod text;
 
 pub use curves::{MAX_SPLINE_POINTS, conic_point, ellipse_point, spline_end_tangent, spline_polyline};
 pub use link::{Link, LinkGeom, LinkKind, LinkSource, MAX_LINK_ENTITIES};
@@ -22,6 +23,7 @@ pub use model::{Constraint, ConstraintKind, Curve, CurveKind, SPoint, Sketch, Sk
 pub use profiles::{Profile, find_drawn_profiles, find_profiles, merge_regions};
 pub use shape::{Shape, intersections};
 pub use solver::{SolveReport, SolveStatus, solve};
+pub use text::{MAX_TEXT_CHARS, text_geometry};
 
 #[cfg(test)]
 mod tests;

crates/sketch/src/link.rs

@@ -27,6 +27,8 @@ pub enum LinkKind {
     Include,
     /// Section curves of a body or face with the sketch plane.
     Intersect,
+    /// Text outlines (drawn like normal geometry; edit the text to change them).
+    Text,
 }
 
 /// What a link refers to. Model geometry is referenced by a point on it plus the body name and
@@ -53,6 +55,14 @@ pub enum LinkSource {
     /// An origin plane (`XY`, `XZ`, `YZ`) or a construction plane (by name): its trace on the
     /// sketch plane.
     Plane { name: String },
+    /// Text: baseline start `at` (sketch coordinates), capital height and angle (radians).
+    Text {
+        text: String,
+        at: Vec2,
+        height: f64,
+        #[serde(default)]
+        angle: f64,
+    },
 }
 
 impl LinkSource {
@@ -68,6 +78,7 @@ impl LinkSource {
             LinkSource::Origin => "origin".into(),
             LinkSource::Axis { name } => format!("{name} axis"),
             LinkSource::Plane { name } => format!("{name} plane"),
+            LinkSource::Text { text, .. } => format!("text \"{}\"", text.chars().take(20).collect::<String>()),
         }
     }
 }
@@ -96,6 +107,13 @@ pub enum LinkGeom {
         a: Vec2,
         b: Vec2,
     },
+    /// Conic from `a` to `b` with control `apex` (rho 0.5: a quadratic Bézier).
+    Conic {
+        a: Vec2,
+        apex: Vec2,
+        b: Vec2,
+        rho: f64,
+    },
 }
 
 impl LinkGeom {
@@ -106,6 +124,7 @@ impl LinkGeom {
             LinkGeom::Line(a, b) => ok(a) && ok(b) && a.dist(*b) > MERGE_TOL,
             LinkGeom::Circle(c, r) => ok(c) && r.is_finite() && *r > 1e-9 && *r < 1e9,
             LinkGeom::Arc { c, a, b } => ok(c) && ok(a) && ok(b) && c.dist(*a) > 1e-9 && a.dist(*b) > MERGE_TOL,
+            LinkGeom::Conic { a, apex, b, rho } => ok(a) && ok(apex) && ok(b) && a.dist(*b) > MERGE_TOL && *rho > 1e-6 && *rho < 1.0 - 1e-6,
         }
     }
 }
@@ -123,6 +142,7 @@ enum LCurve {
     Line(usize, usize),
     Circle(usize, f64),
     Arc(usize, usize, usize),
+    Conic(usize, usize, usize, f64),
 }
 
 fn layout(geom: &[LinkGeom]) -> Result<Layout> {
@@ -163,6 +183,12 @@ fn layout(geom: &[LinkGeom]) -> Result<Layout> {
                     l.curves.push(LCurve::Arc(c, a, b));
                 }
             }
+            LinkGeom::Conic { a, apex, b, rho } => {
+                let (a, b, x) = (pt(&mut l.pts, a), pt(&mut l.pts, b), pt(&mut l.pts, apex));
+                if a != b && x != a && x != b {
+                    l.curves.push(LCurve::Conic(a, b, x, rho));
+                }
+            }
         }
     }
     // Lone points that a curve also uses are not lone.
@@ -171,6 +197,7 @@ fn layout(geom: &[LinkGeom]) -> Result<Layout> {
             LCurve::Line(a, b) => a == i || b == i,
             LCurve::Circle(c, _) => c == i,
             LCurve::Arc(c, a, b) => c == i || a == i || b == i,
+            LCurve::Conic(a, b, x, _) => a == i || b == i || x == i,
         })
     };
     let curves = l.curves.clone();
@@ -179,7 +206,13 @@ fn layout(geom: &[LinkGeom]) -> Result<Layout> {
 }
 
 fn same_shape(a: &LCurve, b: &LCurve) -> bool {
-    matches!((a, b), (LCurve::Line(..), LCurve::Line(..)) | (LCurve::Circle(..), LCurve::Circle(..)) | (LCurve::Arc(..), LCurve::Arc(..)))
+    matches!(
+        (a, b),
+        (LCurve::Line(..), LCurve::Line(..))
+            | (LCurve::Circle(..), LCurve::Circle(..))
+            | (LCurve::Arc(..), LCurve::Arc(..))
+            | (LCurve::Conic(..), LCurve::Conic(..))
+    )
 }
 
 impl Sketch {
@@ -202,6 +235,11 @@ impl Sketch {
         self.curves.get(ci).is_some_and(|c| c.link.is_some())
     }
 
+    /// Is this curve text outline (linked, but drawn like normal geometry)?
+    pub fn is_text_curve(&self, ci: usize) -> bool {
+        self.curves.get(ci).and_then(|c| c.link.as_deref()).and_then(|l| self.link(l)).is_some_and(|l| l.kind == LinkKind::Text)
+    }
+
     /// Is the curve's link lost (its reference no longer found)?
     pub fn is_lost_curve(&self, ci: usize) -> bool {
         self.curves.get(ci).and_then(|c| c.link.as_deref()).and_then(|l| self.link(l)).is_some_and(|l| l.lost)
@@ -245,6 +283,7 @@ impl Sketch {
                 LCurve::Line(a, b) => (CurveKind::Line { a: point(self, a)?, b: point(self, b)? }, "l"),
                 LCurve::Circle(c, r) => (CurveKind::Circle { c: point(self, c)?, r }, "c"),
                 LCurve::Arc(c, a, b) => (CurveKind::Arc { c: point(self, c)?, a: point(self, a)?, b: point(self, b)? }, "a"),
+                LCurve::Conic(a, b, x, rho) => (CurveKind::Conic { a: point(self, a)?, b: point(self, b)?, apex: point(self, x)?, rho }, "k"),
             };
             let cid = self.fresh(prefix);
             self.curves.push(Curve { id: cid, kind, construction: false, reversed: false, link: Some(id.to_string()) });
@@ -274,6 +313,7 @@ impl Sketch {
                 Some(CurveKind::Line { a, b }) => Some(LCurve::Line(local(*a)?, local(*b)?)),
                 Some(CurveKind::Circle { c, r }) => Some(LCurve::Circle(local(*c)?, *r)),
                 Some(CurveKind::Arc { c, a, b }) => Some(LCurve::Arc(local(*c)?, local(*a)?, local(*b)?)),
+                Some(CurveKind::Conic { a, b, apex, rho }) => Some(LCurve::Conic(local(*a)?, local(*b)?, local(*apex)?, *rho)),
                 _ => None,
             })
             .collect();
@@ -297,6 +337,11 @@ impl Sketch {
                     visit(a);
                     visit(b);
                 }
+                LCurve::Conic(a, b, x, _) => {
+                    visit(a);
+                    visit(b);
+                    visit(x);
+                }
             }
         }
         for i in &lay.lone {
@@ -310,6 +355,7 @@ impl Sketch {
                 LCurve::Line(a, b) => LCurve::Line(renum(a), renum(b)),
                 LCurve::Circle(c, r) => LCurve::Circle(renum(c), r),
                 LCurve::Arc(c, a, b) => LCurve::Arc(renum(c), renum(a), renum(b)),
+                LCurve::Conic(a, b, x, r) => LCurve::Conic(renum(a), renum(b), renum(x), r),
             })
             .collect();
         let same = match &cur {
@@ -322,6 +368,7 @@ impl Sketch {
                                 (LCurve::Line(a0, a1), LCurve::Line(b0, b1)) => a0 == b0 && a1 == b1,
                                 (LCurve::Circle(a0, _), LCurve::Circle(b0, _)) => a0 == b0,
                                 (LCurve::Arc(a0, a1, a2), LCurve::Arc(b0, b1, b2)) => a0 == b0 && a1 == b1 && a2 == b2,
+                                (LCurve::Conic(a0, a1, a2, _), LCurve::Conic(b0, b1, b2, _)) => a0 == b0 && a1 == b1 && a2 == b2,
                                 _ => false,
                             }
                     })
@@ -342,6 +389,9 @@ impl Sketch {
                 if let (LCurve::Circle(_, r), Some(Curve { kind: CurveKind::Circle { r: slot, .. }, .. })) = (c, self.curves.get_mut(*ci)) {
                     *slot = *r;
                 }
+                if let (LCurve::Conic(.., r), Some(Curve { kind: CurveKind::Conic { rho, .. }, .. })) = (c, self.curves.get_mut(*ci)) {
+                    *rho = *r;
+                }
             }
             return Ok(false);
         }

crates/sketch/src/text.rs

@@ -0,0 +1,129 @@
+//! Sketch text: glyph outlines of an embedded open font (Liberation Sans, SIL OFL 1.1; see
+//! `fonts/OFL.txt` and ATTRIBUTION.md) as lines and conics (TrueType quadratic Béziers are
+//! conics with rho = 0.5), so text closes into profiles that can be extruded.
+
+use solvecraft_geom::Vec2;
+
+use crate::link::LinkGeom;
+use crate::model::{Result, SketchError};
+
+static FONT: &[u8] = include_bytes!("../fonts/LiberationSans-Regular.ttf");
+
+/// Most characters in one text.
+pub const MAX_TEXT_CHARS: usize = 1000;
+
+struct Outline {
+    out: Vec<LinkGeom>,
+    start: Vec2,
+    cur: Vec2,
+    map: Box<dyn Fn(f32, f32) -> Vec2>,
+}
+
+impl Outline {
+    fn line(&mut self, to: Vec2) {
+        if self.cur.dist(to) > 1e-9 {
+            self.out.push(LinkGeom::Line(self.cur, to));
+        }
+        self.cur = to;
+    }
+    fn quad(&mut self, apex: Vec2, to: Vec2) {
+        let (a, b) = (self.cur, to);
+        let chord = b - a;
+        let off = chord.cross(apex - a).abs() / chord.len().max(1e-12);
+        if off < 1e-6 || a.dist(b) < 1e-9 {
+            self.line(to);
+            return;
+        }
+        self.out.push(LinkGeom::Conic { a, apex, b, rho: 0.5 });
+        self.cur = to;
+    }
+}
+
+impl ttf_parser::OutlineBuilder for Outline {
+    fn move_to(&mut self, x: f32, y: f32) {
+        let p = (self.map)(x, y);
+        self.start = p;
+        self.cur = p;
+    }
+    fn line_to(&mut self, x: f32, y: f32) {
+        let p = (self.map)(x, y);
+        self.line(p);
+    }
+    fn quad_to(&mut self, x1: f32, y1: f32, x: f32, y: f32) {
+        let (c, p) = ((self.map)(x1, y1), (self.map)(x, y));
+        self.quad(c, p);
+    }
+    fn curve_to(&mut self, x1: f32, y1: f32, x2: f32, y2: f32, x: f32, y: f32) {
+        // A cubic as two quadratics (split at the middle).
+        let (p0, c1, c2, p3) = (self.cur, (self.map)(x1, y1), (self.map)(x2, y2), (self.map)(x, y));
+        let mid = (p0 + c1 * 3.0 + c2 * 3.0 + p3) / 8.0;
+        let q1 = p0 + (c1 - p0) * 0.75;
+        let q2 = p3 + (c2 - p3) * 0.75;
+        self.quad(q1, mid);
+        self.quad(q2, p3);
+    }
+    fn close(&mut self) {
+        let s = self.start;
+        self.line(s);
+    }
+}
+
+/// Outline geometry of `text` with its baseline starting at `at`, capital height `height`
+/// (mm), rotated by `angle` (radians) about `at`. Lines break at `\n`.
+pub fn text_geometry(text: &str, at: Vec2, height: f64, angle: f64) -> Result<Vec<LinkGeom>> {
+    if text.chars().count() > MAX_TEXT_CHARS {
+        return Err(SketchError::TooLarge);
+    }
+    if !(height.is_finite() && height > 1e-6 && height < 1e6) || !angle.is_finite() || !at.is_finite() {
+        return Err(SketchError::Invalid("text height must be positive".into()));
+    }
+    let face = ttf_parser::Face::parse(FONT, 0).map_err(|e| SketchError::Invalid(format!("font: {e}")))?;
+    let cap = face.capital_height().map(f64::from).filter(|c| *c > 0.0).unwrap_or(f64::from(face.units_per_em()) * 0.7);
+    let k = height / cap;
+    let line_gap = f64::from(face.ascender() - face.descender() + face.line_gap()) * k;
+    let (s, c) = angle.sin_cos();
+    let mut out = Vec::new();
+    for (row, line) in text.split('\n').enumerate() {
+        let mut pen = 0.0f64;
+        let base_y = -(row as f64) * line_gap;
+        for ch in line.chars() {
+            let Some(gid) = face.glyph_index(ch).or_else(|| face.glyph_index('?')) else { continue };
+            let x0 = pen;
+            let map = Box::new(move |x: f32, y: f32| {
+                let (lx, ly) = (x0 + f64::from(x) * k, base_y + f64::from(y) * k);
+                at + Vec2::new(lx * c - ly * s, lx * s + ly * c)
+            });
+            let mut ob = Outline { out: Vec::new(), start: at, cur: at, map };
+            let _ = face.outline_glyph(gid, &mut ob);
+            out.extend(ob.out);
+            pen += f64::from(face.glyph_hor_advance(gid).unwrap_or(0)) * k;
+        }
+    }
+    Ok(out)
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn letters_have_closed_outlines_at_the_cap_height() {
+        let g = text_geometry("HO", Vec2::new(5.0, 0.0), 10.0, 0.0).unwrap();
+        assert!(!g.is_empty());
+        let ys: Vec<f64> = g
+            .iter()
+            .flat_map(|x| match *x {
+                LinkGeom::Line(a, b) => vec![a.y, b.y],
+                LinkGeom::Conic { a, b, .. } => vec![a.y, b.y],
+                _ => vec![],
+            })
+            .collect();
+        let top = ys.iter().cloned().fold(f64::MIN, f64::max);
+        assert!((top - 10.0).abs() < 0.3, "{top}");
+        assert!(g.iter().any(|x| matches!(x, LinkGeom::Conic { .. })), "O has curves");
+        assert!(text_geometry("x", Vec2::ZERO, -1.0, 0.0).is_err());
+        assert!(text_geometry(&"x".repeat(2000), Vec2::ZERO, 1.0, 0.0).is_err());
+        // Empty text makes nothing (not an error here; the command rejects it).
+        assert!(text_geometry("", Vec2::ZERO, 1.0, 0.0).unwrap().is_empty());
+    }
+}