Fix modelling regressions and reconcile WIP UI work

crates/sketch/src/offset.rs

@@ -0,0 +1,116 @@
+//! Associative offsets keep their output entity ids while their source curves move.
+use crate::{CurveKind, Shape, Sketch, SketchError, intersections};
+use serde::{Deserialize, Serialize};
+use solvecraft_geom::Vec2;
+
+#[derive(Clone, Debug, PartialEq, Serialize, Deserialize)]
+pub struct OffsetChain {
+    pub sources: Vec<(String, bool)>,
+    pub outputs: Vec<String>,
+    pub distance: f64,
+    pub closed: bool,
+}
+
+impl Sketch {
+    pub fn refresh_offsets(&mut self) -> Result<(), SketchError> {
+        for offset in self.offsets.clone() {
+            if offset.sources.len() != offset.outputs.len() || offset.sources.len() > 10_000 || !offset.distance.is_finite() {
+                return Err(SketchError::Invalid("damaged offset chain".into()));
+            }
+            let bad = || SketchError::Invalid("an offset source vanished or changed shape".into());
+            let mut pieces = Vec::new();
+            for (id, forward) in &offset.sources {
+                let i = self.curve_index(id).ok_or_else(bad)?;
+                let kind = &self.curves.get(i).ok_or_else(bad)?.kind;
+                let piece = match *kind {
+                    CurveKind::Line { a, b } => {
+                        let (a, b) = (self.point(a).ok_or_else(bad)?, self.point(b).ok_or_else(bad)?);
+                        let (a, b) = if *forward { (a, b) } else { (b, a) };
+                        let n = (b - a).normalized().ok_or_else(bad)?.perp() * offset.distance;
+                        (Shape::Line { a: a + n, b: b + n }, a + n, b + n)
+                    }
+                    CurveKind::Arc { c, a, b } => {
+                        let (c, a, b) = (self.point(c).ok_or_else(bad)?, self.point(a).ok_or_else(bad)?, self.point(b).ok_or_else(bad)?);
+                        let r = c.dist(a) - if *forward { offset.distance } else { -offset.distance };
+                        if r <= 1e-9 {
+                            return Err(SketchError::Invalid("the offset collapses an arc".into()));
+                        }
+                        let a = c + (a - c).normalized().ok_or_else(bad)? * r;
+                        let b = c + (b - c).normalized().ok_or_else(bad)? * r;
+                        let (a, b) = if *forward { (a, b) } else { (b, a) };
+                        (Shape::Round { c, r, start: 0.0, sweep: std::f64::consts::TAU }, a, b)
+                    }
+                    CurveKind::Circle { c, r } => {
+                        let c = self.point(c).ok_or_else(bad)?;
+                        let r = r - offset.distance;
+                        if r <= 1e-9 {
+                            return Err(SketchError::Invalid("the offset collapses a circle".into()));
+                        }
+                        let out = offset.outputs.first().and_then(|id| self.curve_index(id)).ok_or_else(bad)?;
+                        if let Some(crate::Curve { kind: CurveKind::Circle { r: target, .. }, .. }) = self.curves.get_mut(out) {
+                            *target = r;
+                        } else {
+                            return Err(bad());
+                        }
+                        let _ = c;
+                        continue;
+                    }
+                    _ => return Err(bad()),
+                };
+                pieces.push(piece);
+            }
+            if pieces.is_empty() {
+                continue;
+            }
+            let joint = |i: usize, j: usize| -> Result<Vec2, SketchError> {
+                let (x, y) = (pieces.get(i).ok_or_else(bad)?, pieces.get(j).ok_or_else(bad)?);
+                if x.2.dist(y.1) < 1e-6 {
+                    return Ok(x.2);
+                }
+                let guess = (x.2 + y.1) * 0.5;
+                intersections(&x.0, &y.0)
+                    .into_iter()
+                    .min_by(|a, b| a.dist(guess).total_cmp(&b.dist(guess)))
+                    .ok_or_else(|| SketchError::Invalid("the offset curves no longer meet".into()))
+            };
+            let n = pieces.len();
+            let mut joints = vec![if offset.closed { joint(n - 1, 0)? } else { pieces.first().ok_or_else(bad)?.1 }];
+            for i in 0..n.saturating_sub(1) {
+                joints.push(joint(i, i + 1)?);
+            }
+            if !offset.closed {
+                joints.push(pieces.last().ok_or_else(bad)?.2);
+            }
+            for (i, id) in offset.outputs.iter().enumerate() {
+                let a = *joints.get(i).ok_or_else(bad)?;
+                let b = *joints.get(if offset.closed { (i + 1) % n } else { i + 1 }).ok_or_else(bad)?;
+                let shape = &pieces.get(i).ok_or_else(bad)?.0;
+                if let Shape::Line { a: p, b: q } = shape
+                    && (b - a).dot(*q - *p) <= 1e-9
+                {
+                    return Err(SketchError::Invalid("the offset curves would cross".into()));
+                }
+                let ci = self.curve_index(id).ok_or_else(bad)?;
+                let kind = self.curves.get(ci).ok_or_else(bad)?.kind.clone();
+                let (pa, pb) = match kind {
+                    CurveKind::Line { a, b } => (a, b),
+                    CurveKind::Arc { a, b, .. } => {
+                        if offset.sources.get(i).is_some_and(|x| x.1) {
+                            (a, b)
+                        } else {
+                            (b, a)
+                        }
+                    }
+                    _ => return Err(bad()),
+                };
+                for (pi, pos) in [(pa, a), (pb, b)] {
+                    if let Some(p) = self.points.get_mut(pi) {
+                        p.pos = pos;
+                        p.fixed = true;
+                    }
+                }
+            }
+        }
+        Ok(())
+    }
+}