Gradient Part 5b: Fix gradients in math (#2604)

crates/typst-library/src/math/cancel.rs

@@ -108,7 +108,7 @@ impl LayoutMath for CancelElem {
         let length = self.length(styles).resolve(styles);
 
         let stroke = self.stroke(styles).unwrap_or(FixedStroke {
-            paint: TextElem::fill_in(styles),
+            paint: TextElem::fill_in(styles).as_decoration(),
             ..Default::default()
         });
 

crates/typst-library/src/math/frac.rs

@@ -143,7 +143,7 @@ fn layout(
             line_pos,
             FrameItem::Shape(
                 Geometry::Line(Point::with_x(line_width)).stroked(FixedStroke {
-                    paint: TextElem::fill_in(ctx.styles()),
+                    paint: TextElem::fill_in(ctx.styles()).as_decoration(),
                     thickness,
                     ..FixedStroke::default()
                 }),

crates/typst-library/src/math/fragment.rs

@@ -225,7 +225,7 @@ impl GlyphFragment {
             c,
             font: ctx.font.clone(),
             lang: TextElem::lang_in(ctx.styles()),
-            fill: TextElem::fill_in(ctx.styles()),
+            fill: TextElem::fill_in(ctx.styles()).as_decoration(),
             shift: TextElem::baseline_in(ctx.styles()),
             style: ctx.style,
             font_size: ctx.size,

crates/typst-library/src/math/matrix.rs

@@ -397,7 +397,7 @@ fn layout_mat_body(
     let default_stroke_thickness = DEFAULT_STROKE_THICKNESS.scaled(ctx);
     let default_stroke = FixedStroke {
         thickness: default_stroke_thickness,
-        paint: TextElem::fill_in(ctx.styles()),
+        paint: TextElem::fill_in(ctx.styles()).as_decoration(),
         line_cap: LineCap::Square,
         ..Default::default()
     };

crates/typst-library/src/math/root.rs

@@ -122,7 +122,7 @@ fn layout(
         line_pos,
         FrameItem::Shape(
             Geometry::Line(Point::with_x(radicand.width())).stroked(FixedStroke {
-                paint: TextElem::fill_in(ctx.styles()),
+                paint: TextElem::fill_in(ctx.styles()).as_decoration(),
                 thickness,
                 ..FixedStroke::default()
             }),

crates/typst-library/src/math/underover.rs

@@ -96,7 +96,7 @@ fn layout_underoverline(
         line_pos,
         FrameItem::Shape(
             Geometry::Line(Point::with_x(width)).stroked(FixedStroke {
-                paint: TextElem::fill_in(ctx.styles()),
+                paint: TextElem::fill_in(ctx.styles()).as_decoration(),
                 thickness: bar_height,
                 ..FixedStroke::default()
             }),

tests/typ/visualize/gradient-math.typ

@@ -0,0 +1,68 @@
+// Test that gradients are applied correctly on equations.
+
+---
+// Test on cancel
+#show math.equation: set text(fill: gradient.linear(..color.map.rainbow))
+#show math.equation: box
+
+$ a dot cancel(5) = cancel(25) 5 x + cancel(5) 1 $
+
+---
+// Test on frac
+#show math.equation: set text(fill: gradient.linear(..color.map.rainbow))
+#show math.equation: box
+
+$ nabla dot bold(E) = frac(rho, epsilon_0) $
+
+---
+// Test on root
+#show math.equation: set text(fill: gradient.linear(..color.map.rainbow))
+#show math.equation: box
+
+$ x_"1,2" = frac(-b +- sqrt(b^2 - 4 a c), 2 a) $
+
+---
+// Test on matrix
+#show math.equation: set text(fill: gradient.linear(..color.map.rainbow))
+#show math.equation: box
+
+$ A = mat(
+  1, 2, 3;
+  4, 5, 6;
+  7, 8, 9
+) $
+
+---
+// Test on underover
+#show math.equation: set text(fill: gradient.linear(..color.map.rainbow))
+#show math.equation: box
+
+$ underline(X^2) $
+$ overline("hello, world!") $
+
+---
+// Test a different direction
+#show math.equation: set text(fill: gradient.linear(..color.map.rainbow, dir: ttb))
+#show math.equation: box
+
+$ A = mat(
+  1, 2, 3;
+  4, 5, 6;
+  7, 8, 9
+) $
+
+$ x_"1,2" = frac(-b +- sqrt(b^2 - 4 a c), 2 a) $
+
+---
+// Test miscelaneous
+
+#show math.equation: set text(fill: gradient.linear(..color.map.rainbow))
+#show math.equation: box
+
+$ hat(x) = bar x bar = vec(x, y, z) = tilde(x) = dot(x) $
+$ x prime = vec(1, 2, delim: "[") $
+$ sum_(i in NN) 1 + i $
+$ attach(
+  Pi, t: alpha, b: beta,
+  tl: 1, tr: 2+3, bl: 4+5, br: 6,
+) $