Fixed symbol style reset in stretching (#1195)

library/src/math/fragment.rs

@@ -164,6 +164,32 @@ impl GlyphFragment {
     }
 
     pub fn with_id(ctx: &MathContext, c: char, id: GlyphId, span: Span) -> Self {
+        let mut fragment = Self {
+            id,
+            c,
+            font: ctx.font.clone(),
+            lang: TextElem::lang_in(ctx.styles()),
+            fill: TextElem::fill_in(ctx.styles()),
+            style: ctx.style,
+            font_size: ctx.size,
+            width: Abs::zero(),
+            ascent: Abs::zero(),
+            descent: Abs::zero(),
+            italics_correction: Abs::zero(),
+            class: match c {
+                ':' => Some(MathClass::Relation),
+                _ => unicode_math_class::class(c),
+            },
+            span,
+            meta: MetaElem::data_in(ctx.styles()),
+        };
+        fragment.set_id(ctx, id);
+        fragment
+    }
+
+    /// Sets element id and boxes in appropriate way without changing other
+    /// styles. This is used to replace the glyph with a stretch variant.
+    pub fn set_id(&mut self, ctx: &MathContext, id: GlyphId) {
         let advance = ctx.ttf.glyph_hor_advance(id).unwrap_or_default();
         let italics = italics_correction(ctx, id).unwrap_or_default();
         let bbox = ctx.ttf.glyph_bounding_box(id).unwrap_or(Rect {
@@ -178,25 +204,11 @@ impl GlyphFragment {
             width += italics;
         }
 
-        Self {
-            id,
-            c,
-            font: ctx.font.clone(),
-            lang: TextElem::lang_in(ctx.styles()),
-            fill: TextElem::fill_in(ctx.styles()),
-            style: ctx.style,
-            font_size: ctx.size,
-            width,
-            ascent: bbox.y_max.scaled(ctx),
-            descent: -bbox.y_min.scaled(ctx),
-            italics_correction: italics,
-            class: match c {
-                ':' => Some(MathClass::Relation),
-                _ => unicode_math_class::class(c),
-            },
-            span,
-            meta: MetaElem::data_in(ctx.styles()),
-        }
+        self.id = id;
+        self.width = width;
+        self.ascent = bbox.y_max.scaled(ctx);
+        self.descent = -bbox.y_min.scaled(ctx);
+        self.italics_correction = italics;
     }
 
     pub fn height(&self) -> Abs {

library/src/math/stretch.rs

@@ -33,7 +33,7 @@ impl GlyphFragment {
 /// The resulting frame may not have the exact desired width.
 fn stretch_glyph(
     ctx: &MathContext,
-    base: GlyphFragment,
+    mut base: GlyphFragment,
     target: Abs,
     short_fall: Abs,
     horizontal: bool,
@@ -73,7 +73,8 @@ fn stretch_glyph(
 
     // This is either good or the best we've got.
     if short_target <= best_advance || construction.assembly.is_none() {
-        return GlyphFragment::with_id(ctx, base.c, best_id, base.span).into_variant();
+        base.set_id(ctx, best_id);
+        return base.into_variant();
     }
 
     // Assemble from parts.
@@ -142,7 +143,8 @@ fn assemble(
             advance += ratio * (max_overlap - min_overlap);
         }
 
-        let fragment = GlyphFragment::with_id(ctx, base.c, part.glyph_id, base.span);
+        let mut fragment = base.clone();
+        fragment.set_id(ctx, part.glyph_id);
         selected.push((fragment, advance));
     }
 

tests/typ/math/delimited.typ

@@ -36,3 +36,10 @@ $ lr(]sum_(x=1)^n x], size: #70%)
 ---
 // Test predefined delimiter pairings.
 $floor(x/2), ceil(x/2), abs(x), norm(x)$
+
+---
+// Test colored delimiters
+$ lr(
+    text("(", fill: #green) a/b
+    text(")", fill: #blue)
+  ) $