Merge main into feat/plugin-effect-paint

crates/doc/src/node/live_shape.rs

@@ -329,6 +329,10 @@ pub struct Scaling {
     /// Pattern fills and strokes move with the art (Transform Patterns; General › Transform
     /// Pattern Tiles is its default): their tiles transform too, instead of staying put.
     pub patterns: bool,
+    /// Gradients fitted to the object stay fitted under a transform that flattens it to a line or
+    /// a point (no area left), as a Transform effect leaves them, instead of being fixed to their
+    /// fit and flattened to one color with the object.
+    pub keep_fit_when_flat: bool,
 }
 
 impl Scaling {

crates/doc/src/node/ops.rs

@@ -433,7 +433,7 @@ impl Node {
         // Type and symbols in perspective keep looking the same, moved by `a`.
         self.transform_projection(a);
         // Refitting an unplaced gradient only reproduces moves and uniform scales.
-        if !keeps_gradient_fit(a) {
+        if !keeps_gradient_fit(a) && !(sc.keep_fit_when_flat && flattens(a)) {
             self.pin_gradients();
         }
         let k = Scaling::factor(a);
@@ -772,13 +772,24 @@ impl Node {
     }
 }
 
-/// Is `a` a move plus a positive uniform scale (after which a refit gradient still matches)?
-fn keeps_gradient_fit(a: Affine) -> bool {
+/// Is `a` a move plus a positive uniform scale (after which a refit gradient still matches)? The
+/// terms are compared within 1e-12 of the scale (at least of 1). A scale of 0 or less, a turn, a
+/// reflection and an uneven scale give false, and so does a map that flattens the object
+/// ([`flattens`]), which callers that keep a fitted gradient there check apart.
+pub fn keeps_gradient_fit(a: Affine) -> bool {
     let [m0, m1, m2, m3, _, _] = a.as_coeffs();
     let eps = 1e-12 * m0.abs().max(1.0);
     m0 > 0.0 && m1.abs() <= eps && m2.abs() <= eps && (m0 - m3).abs() <= eps
 }
 
+/// Does `a` flatten what it maps to a line or a point (its determinant 0, within 1e-12 of the
+/// squares of its terms), or is it not finite?
+pub fn flattens(a: Affine) -> bool {
+    let [m0, m1, m2, m3, _, _] = a.as_coeffs();
+    let norm = m0 * m0 + m1 * m1 + m2 * m2 + m3 * m3;
+    !a.is_finite() || a.determinant().abs() <= 1e-12 * norm
+}
+
 impl Node {
     /// Whether a document point lies in this object's filled regions ([`Node::clip_shapes`]; true
     /// everywhere for objects without them, such as type, whose boxes stand in).

crates/doc/src/node/tests.rs

@@ -221,7 +221,8 @@ fn assert_round_corners(n: &Node, back: Affine, r: f64) {
     }
 }
 
-const KEEP_CORNERS: Scaling = Scaling { strokes: false, effects: None, keep_type_strokes: false, keep_corners: true, patterns: false };
+const KEEP_CORNERS: Scaling =
+    Scaling { strokes: false, effects: None, keep_type_strokes: false, keep_corners: true, patterns: false, keep_fit_when_flat: false };
 
 #[test]
 fn uneven_scales_keep_live_corners_circular() {