fix: handle latex equations when rendering typst

src/export/typst/config.rs

@@ -607,6 +607,8 @@ defaults:
   extra:
     accent: '#017ab9'
     font: 'Libertinus Serif'
+    show-bubbles: true
+    bubble-radius: '0.42em'
 
 variants:
   exam:

src/export/typst/payload.rs

@@ -1070,8 +1070,61 @@ fn numeric_map(map: &BTreeMap<String, f64>) -> Value {
     )
 }
 
-/// Emits authored markup as either a content block or a quoted string.
+/// Rewrites inline LaTeX math (`$...$`) into a call to mitex's `mi`, so Typst's
+/// own math grammar never has to parse it. Typst's `\times`, `\Delta`, `\ln` and
+/// friends are not valid Typst math — a bare backslash escapes the next
+/// character instead of naming a symbol — which is why equations compile but
+/// print wrong instead of failing outright. `\$` is left alone, matching LaTeX's
+/// own convention for a literal dollar sign, and a `$` with no matching close is
+/// left alone too, rather than swallowing the rest of the field.
+fn rewrite_latex_math(source: &str) -> String {
+    let chars: Vec<(usize, char)> = source.char_indices().collect();
+    let mut out = String::with_capacity(source.len());
+    let mut i = 0;
+    while i < chars.len() {
+        let (_, c) = chars[i];
+        if c == '\\' && i + 1 < chars.len() {
+            out.push('\\');
+            out.push(chars[i + 1].1);
+            i += 2;
+            continue;
+        }
+        if c != '$' {
+            out.push(c);
+            i += 1;
+            continue;
+        }
+        let mut j = i + 1;
+        let close = loop {
+            if j >= chars.len() {
+                break None;
+            }
+            match chars[j].1 {
+                '\\' => j += 2,
+                '$' => break Some(j),
+                _ => j += 1,
+            }
+        };
+        match close {
+            Some(close_idx) => {
+                let start = chars[i + 1].0;
+                let end = chars[close_idx].0;
+                out.push_str("#mi(");
+                out.push_str(&Value::str(&source[start..end]).to_typst(0));
+                out.push(')');
+                i = close_idx + 1;
+            }
+            None => {
+                out.push('$');
+                i += 1;
+            }
+        }
+    }
+    out
+}
+
 fn markup_value(source: &str, content: bool) -> Value {
+    let source = rewrite_latex_math(source);
     if content {
         Value::content(source)
     } else {
@@ -1221,3 +1274,17 @@ mod tests {
         assert!(!balanced("closing ] first"));
     }
 }
+
+#[test]
+fn latex_math_becomes_a_mitex_call() {
+    assert_eq!(
+        rewrite_latex_math("angle $\\phi$ (phi)"),
+        "angle #mi(\"\\\\phi\") (phi)"
+    );
+}
+
+#[test]
+fn escaped_and_unmatched_dollar_signs_are_left_alone() {
+    assert_eq!(rewrite_latex_math("costs \\$5 total"), "costs \\$5 total");
+    assert_eq!(rewrite_latex_math("just $5"), "just $5");
+}

src/export/typst/templates/answer-sheet.typ

@@ -12,6 +12,8 @@
 // templates/typst.yaml under `extra` rather than editing the geometry here, and
 // check one printed page against your scanner before running a class through it.
 
+#import "@preview/mitex:0.2.7": mi
+
 // coursebank:begin data
 #let cb-data = (
   course: (code: "COURSE 101", title: "Sample Course", term: "2026s"),

src/export/typst/templates/exam.typ

@@ -24,6 +24,8 @@
 // copy — export the `key` variant instead, or the day you forget an `if` is the
 // day the class gets the answers.
 
+#import "@preview/mitex:0.2.7": mi
+
 // ─────────────────────────────────────────────────────────────────────────────
 // Metadata
 // ─────────────────────────────────────────────────────────────────────────────
@@ -52,12 +54,14 @@
 // how a course changes the look without editing this file at all.
 #let extra = cb-meta.at("extra", default: (:))
 #let accent = rgb(extra.at("accent", default: "#1f4e79"))
-#let body-font = extra.at("font", default: "Libertinus Serif")
+#let body-font = extra.at("font", default: "Roboto")
 #let body-size = eval(extra.at("font-size", default: "11pt"))
 #let paper = extra.at("paper", default: "us-letter")
 #let show-name-block = extra.at("name-block", default: true)
 #let show-points = extra.at("show-points", default: true)
 #let page-per-item = extra.at("page-per-item", default: false)
+#let show-bubbles = extra.at("show-bubbles", default: true)
+#let bubble-radius = eval(extra.at("bubble-radius", default: "0.42em"))
 
 #let form-note = if cb-meta.form.at("count", default: 1) > 1 {
   " · Form " + cb-meta.form.id
@@ -120,6 +124,11 @@
   }
 }
 
+// An unfilled bubble a student marks by hand. `bubble-radius` is the same knob
+// the standalone answer sheet reads, so the two stay visually consistent if you
+// ever generate both.
+#let bubble() = circle(radius: bubble-radius, stroke: 0.5pt)
+
 // ─────────────────────────────────────────────────────────────────────────────
 // The renderer
 // ─────────────────────────────────────────────────────────────────────────────
@@ -154,11 +163,19 @@
 
   block(inset: (left: 1.2em))[
     #for opt in q.at("options", default: ()) {
-      grid(
-        columns: (1.4em, 1fr),
-        gutter: 0.2em,
-        [#(opt.letter + ".")], [#markup(opt.text)],
-      )
+      if show-bubbles {
+        grid(
+          columns: (1.6em, 1.4em, 1fr),
+          gutter: 0.2em,
+          align(horizon)[#bubble()], [#(opt.letter + ".")], [#markup(opt.text)],
+        )
+      } else {
+        grid(
+          columns: (1.4em, 1fr),
+          gutter: 0.2em,
+          [#(opt.letter + ".")], [#markup(opt.text)],
+        )
+      }
       v(0.15em)
     }
   ]

src/export/typst/templates/key.typ

@@ -13,6 +13,8 @@
 // paper's config, and it is why these are two templates rather than one with a
 // flag.
 
+#import "@preview/mitex:0.2.7": mi
+
 // coursebank:begin data
 #let cb-data = (
   course: (code: "COURSE 101", title: "Sample Course", term: "2026s"),