typography and documents: formula and diagram SVG for export; a diagram label without a font is an error

src/typography/math.rs

@@ -116,6 +116,18 @@ impl Asset for Typesetter {
     }
 }
 
+/// `source` as black outlined SVG, for export.
+pub fn formula_svg(source: &str, display: bool) -> Result<String, MathError> {
+    let formula = Formula {
+        source: source.to_owned().into(),
+        display,
+        rgba: 0x0000_00ff,
+        font: 1600,
+        scale: 100,
+    };
+    svg(&formula).map(|(svg, _)| svg)
+}
+
 /// The formula as outlined SVG holding all ink; its size.
 fn svg(formula: &Formula) -> Result<(String, Size<Pixels>), MathError> {
     let ast = parsed(&formula.source)?;

src/typography/math/tests.rs

@@ -177,3 +177,11 @@ fn a_shared_formula_stays_until_its_last_holder_leaves(cx: &mut gpui::TestAppCon
     flush(cx);
     assert!(!cached("c^2", cx), "the last holder freed it");
 }
+
+#[test]
+fn an_exported_formula_is_black_outlines() {
+    let svg = formula_svg(r"\sqrt{x}", true).expect("typesets");
+    assert!(svg.starts_with("<svg") && !svg.contains("<text"), "{svg}");
+    assert!(svg.contains("0,0,0"), "black: {svg}");
+    assert!(formula_svg(r"\frac{", false).is_err());
+}

src/typography/mod.rs

@@ -26,7 +26,7 @@ pub use formatted::{
 pub use inline::{Blockquote, Code, Highlight, Kbd, KbdCombo};
 pub use link::{ExternalLink, Link};
 pub(crate) use math::failed;
-pub use math::{Latex, MathError};
+pub use math::{Latex, MathError, formula_svg};
 pub use rolling::AnimatedNumber;
 pub use select::SelectableText;
 pub use text::{Caption, Heading, Label, Overline, Paragraph, Subtitle, Title, literal, tabular};