feat(monospace): add PdfFontHeader builder for xelatex fontspec

src/main/PdfFontHeader.js

@@ -0,0 +1,43 @@
+'use strict';
+
+// fontspec accepts forward-slash paths on all platforms (TeX normalizes).
+// Normalize Windows backslashes so we can reliably build Path/filename.
+function toPosix(p) {
+  return String(p).replace(/\\/g, '/');
+}
+
+function escape(s) {
+  // fontspec values: braces are the only TeX-significant chars we might emit
+  // from a basename. Backslashes are converted to '/' upstream by toPosix().
+  return String(s).replace(/[{}]/g, '\\$&');
+}
+
+function dirOf(p) {
+  return toPosix(p).replace(/\/[^/]+$/, '') + '/';
+}
+
+function baseName(p) {
+  return toPosix(p).split('/').pop();
+}
+
+// Strip a weight-style suffix from a TTF filename to get the family prefix
+// (e.g. JetBrainsMono-Regular.ttf -> JetBrainsMono). Used as the `\setmonofont`
+// argument so `*-Regular` / `*-Bold` globs resolve to the right files.
+function weightPrefix(p) {
+  return baseName(p).replace(/-(Regular|Bold|Light|Medium|SemiBold|Italic)\.ttf$/i, '');
+}
+
+function build({ fontTtfPath, boldTtfPath, ligatures }) {
+  if (!fontTtfPath) {
+    return '% Monospace font path unavailable; TeX will use its default monospace.\n';
+  }
+
+  const ligValue = ligatures ? 'Ligatures=TeX' : 'Ligatures=NoCommon';
+  const prefix = escape(weightPrefix(fontTtfPath));
+
+  return `\\usepackage{fontspec}
+\\setmonofont[Path=${escape(dirOf(fontTtfPath))},Extension=.ttf,UprightFont=*-Regular,BoldFont=*-Bold,${ligValue}]{${prefix}}
+`;
+}
+
+module.exports = { build };