Fix hiding of math (#587)

library/src/math/mod.rs

@@ -256,6 +256,9 @@ impl Layout for EquationElem {
             frame.size_mut().y = ascent + descent;
         }
 
+        // Apply metadata.
+        frame.meta(styles, false);
+
         Ok(Fragment::frame(frame))
     }
 }

tests/typ/bugs/math-hide.typ

@@ -0,0 +1,16 @@
+// Ensure that the math is properly hidden.
+
+---
+#set page(height: 70pt)
+
+Testing $delta$
+
+$ a^2 + b^2 = c^2 $
+
+#hide[
+  Hello
+
+  $ f(x) := x^2 $
+
+  World $f(x)$
+]