Initial fix for spacing on decorated math operators (#1023)

4 files changed, 28 insertions, 4 deletions

diff --git a/library/src/math/accent.rs b/library/src/math/accent.rs
index 1cd84429..2a650f2e 100644
--- a/library/src/math/accent.rs
+++ b/library/src/math/accent.rs
@@ -58,6 +58,8 @@ impl LayoutMath for AccentElem {
         let base = ctx.layout_fragment(&self.base())?;
         ctx.unstyle();
 
+        // Preserve class to preserve automatic spacing.
+        let base_class = base.class().unwrap_or(MathClass::Normal);
         let base_attach = match &base {
             MathFragment::Glyph(base) => {
                 attachment(ctx, base.id, base.italics_correction)
@@ -93,7 +95,11 @@ impl LayoutMath for AccentElem {
         frame.set_baseline(baseline);
         frame.push_frame(accent_pos, accent);
         frame.push_frame(base_pos, base.into_frame());
-        ctx.push(FrameFragment::new(ctx, frame).with_base_ascent(base_ascent));
+        ctx.push(
+            FrameFragment::new(ctx, frame)
+                .with_class(base_class)
+                .with_base_ascent(base_ascent),
+        );
 
         Ok(())
     }
diff --git a/library/src/math/cancel.rs b/library/src/math/cancel.rs
index edc2ba1e..770f3c65 100644
--- a/library/src/math/cancel.rs
+++ b/library/src/math/cancel.rs
@@ -90,7 +90,10 @@ pub struct CancelElem {
 
 impl LayoutMath for CancelElem {
     fn layout_math(&self, ctx: &mut MathContext) -> SourceResult<()> {
-        let mut body = ctx.layout_frame(&self.body())?;
+        let body = ctx.layout_fragment(&self.body())?;
+        // Use the same math class as the body, in order to preserve automatic spacing around it.
+        let body_class = body.class().unwrap_or(MathClass::Special);
+        let mut body = body.into_frame();
 
         let styles = ctx.styles();
         let body_size = body.size();
@@ -130,7 +133,7 @@ impl LayoutMath for CancelElem {
             body.push_frame(center, second_line);
         }
 
-        ctx.push(FrameFragment::new(ctx, body));
+        ctx.push(FrameFragment::new(ctx, body).with_class(body_class));
 
         Ok(())
     }
diff --git a/library/src/math/row.rs b/library/src/math/row.rs
index 23c9d242..a25178af 100644
--- a/library/src/math/row.rs
+++ b/library/src/math/row.rs
@@ -95,6 +95,20 @@ impl MathRow {
         self.iter().map(MathFragment::descent).max().unwrap_or_default()
     }
 
+    pub fn class(&self) -> MathClass {
+        // Predict the class of the output of 'into_fragment'
+        if self.0.len() == 1 {
+            self.0
+                .first()
+                .and_then(|fragment| fragment.class())
+                .unwrap_or(MathClass::Special)
+        } else {
+            // FrameFragment::new() (inside 'into_fragment' in this branch) defaults
+            // to MathClass::Normal for its class.
+            MathClass::Normal
+        }
+    }
+
     pub fn into_frame(self, ctx: &MathContext) -> Frame {
         let styles = ctx.styles();
         let align = AlignElem::alignment_in(styles).x.resolve(styles);
diff --git a/library/src/math/underover.rs b/library/src/math/underover.rs
index 89ec5cff..3ad2538c 100644
--- a/library/src/math/underover.rs
+++ b/library/src/math/underover.rs
@@ -202,6 +202,7 @@ fn layout(
 ) -> SourceResult<()> {
     let gap = gap.scaled(ctx);
     let body = ctx.layout_row(body)?;
+    let body_class = body.class();
     let glyph = GlyphFragment::new(ctx, c, span);
     let stretched = glyph.stretch_horizontal(ctx, body.width(), Abs::zero());
 
@@ -226,7 +227,7 @@ fn layout(
     }
 
     let frame = stack(ctx, rows, Align::Center, gap, baseline);
-    ctx.push(FrameFragment::new(ctx, frame));
+    ctx.push(FrameFragment::new(ctx, frame).with_class(body_class));
 
     Ok(())
 }