Apply short fall consistently in math when stretching (#6377)

crates/typst-layout/src/math/accent.rs

@@ -46,7 +46,7 @@ pub fn layout_accent(
     // wide in many case.
     let width = elem.size(styles).relative_to(base.width());
     let short_fall = ACCENT_SHORT_FALL.at(glyph.font_size);
-    let variant = glyph.stretch_horizontal(ctx, width, short_fall);
+    let variant = glyph.stretch_horizontal(ctx, width - short_fall);
     let accent = variant.frame;
     let accent_attach = variant.accent_attach.0;
 

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

@@ -110,12 +110,12 @@ fn layout_frac_like(
 
     if binom {
         let mut left = GlyphFragment::new(ctx, styles, '(', span)
-            .stretch_vertical(ctx, height, short_fall);
+            .stretch_vertical(ctx, height - short_fall);
         left.center_on_axis(ctx);
         ctx.push(left);
         ctx.push(FrameFragment::new(styles, frame));
         let mut right = GlyphFragment::new(ctx, styles, ')', span)
-            .stretch_vertical(ctx, height, short_fall);
+            .stretch_vertical(ctx, height - short_fall);
         right.center_on_axis(ctx);
         ctx.push(right);
     } else {

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

@@ -435,13 +435,8 @@ impl GlyphFragment {
     }
 
     /// Try to stretch a glyph to a desired height.
-    pub fn stretch_vertical(
-        self,
-        ctx: &mut MathContext,
-        height: Abs,
-        short_fall: Abs,
-    ) -> VariantFragment {
-        stretch_glyph(ctx, self, height, short_fall, Axis::Y)
+    pub fn stretch_vertical(self, ctx: &mut MathContext, height: Abs) -> VariantFragment {
+        stretch_glyph(ctx, self, height, Axis::Y)
     }
 
     /// Try to stretch a glyph to a desired width.
@@ -449,9 +444,8 @@ impl GlyphFragment {
         self,
         ctx: &mut MathContext,
         width: Abs,
-        short_fall: Abs,
     ) -> VariantFragment {
-        stretch_glyph(ctx, self, width, short_fall, Axis::X)
+        stretch_glyph(ctx, self, width, Axis::X)
     }
 }
 

crates/typst-layout/src/math/mat.rs

@@ -314,7 +314,7 @@ fn layout_delimiters(
 
     if let Some(left) = left {
         let mut left = GlyphFragment::new(ctx, styles, left, span)
-            .stretch_vertical(ctx, target, short_fall);
+            .stretch_vertical(ctx, target - short_fall);
         left.align_on_axis(ctx, delimiter_alignment(left.c));
         ctx.push(left);
     }
@@ -323,7 +323,7 @@ fn layout_delimiters(
 
     if let Some(right) = right {
         let mut right = GlyphFragment::new(ctx, styles, right, span)
-            .stretch_vertical(ctx, target, short_fall);
+            .stretch_vertical(ctx, target - short_fall);
         right.align_on_axis(ctx, delimiter_alignment(right.c));
         ctx.push(right);
     }

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

@@ -50,7 +50,7 @@ pub fn layout_root(
     // Layout root symbol.
     let target = radicand.height() + thickness + gap;
     let sqrt = GlyphFragment::new(ctx, styles, '√', span)
-        .stretch_vertical(ctx, target, Abs::zero())
+        .stretch_vertical(ctx, target)
         .frame;
 
     // Layout the index.

crates/typst-layout/src/math/stretch.rs

@@ -67,8 +67,7 @@ pub fn stretch_fragment(
     let mut variant = stretch_glyph(
         ctx,
         glyph,
-        stretch.relative_to(relative_to_size),
-        short_fall,
+        stretch.relative_to(relative_to_size) - short_fall,
         axis,
     );
 
@@ -120,7 +119,6 @@ pub fn stretch_glyph(
     ctx: &mut MathContext,
     mut base: GlyphFragment,
     target: Abs,
-    short_fall: Abs,
     axis: Axis,
 ) -> VariantFragment {
     // If the base glyph is good enough, use it.
@@ -128,8 +126,7 @@ pub fn stretch_glyph(
         Axis::X => base.width,
         Axis::Y => base.height(),
     };
-    let short_target = target - short_fall;
-    if short_target <= advance {
+    if target <= advance {
         return base.into_variant();
     }
 
@@ -153,13 +150,13 @@ pub fn stretch_glyph(
     for variant in construction.variants {
         best_id = variant.variant_glyph;
         best_advance = base.font.to_em(variant.advance_measurement).at(base.font_size);
-        if short_target <= best_advance {
+        if target <= best_advance {
             break;
         }
     }
 
     // This is either good or the best we've got.
-    if short_target <= best_advance || construction.assembly.is_none() {
+    if target <= best_advance || construction.assembly.is_none() {
         base.set_id(ctx, best_id);
         return base.into_variant();
     }

crates/typst-layout/src/math/text.rs

@@ -159,7 +159,7 @@ fn layout_glyph(
         let mut variant = if math_size == MathSize::Display {
             let height = scaled!(ctx, styles, display_operator_min_height)
                 .max(SQRT_2 * glyph.height());
-            glyph.stretch_vertical(ctx, height, Abs::zero())
+            glyph.stretch_vertical(ctx, height)
         } else {
             glyph.into_variant()
         };

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

@@ -286,7 +286,7 @@ fn layout_underoverspreader(
     let body_class = body.class();
     let body = body.into_fragment(styles);
     let glyph = GlyphFragment::new(ctx, styles, c, span);
-    let stretched = glyph.stretch_horizontal(ctx, body.width(), Abs::zero());
+    let stretched = glyph.stretch_horizontal(ctx, body.width());
 
     let mut rows = vec![];
     let baseline = match position {