engine: hyperref pdftitle/pdfauthor set the PDF document metadata

engine.go

@@ -98,6 +98,8 @@ type Engine struct {
 	hyperColorlinks bool          // colorlinks option: colour link text (else leave it black)
 	hyperURLColor   uint32        // \url/\href colour when colorlinks is on (hyperref urlcolor)
 	hyperLinkColor  uint32        // \hyperlink colour when colorlinks is on (hyperref linkcolor)
+	pdfTitle        string        // \hypersetup{pdftitle=…} → PDF /Info /Title
+	pdfAuthor       string        // \hypersetup{pdfauthor=…} → PDF /Info /Author
 	mathR           mathRendererT // lazily-built go-tex/math renderer (see math.go)
 
 	// paragraph-builder state (horizontal mode at top level)

hyperstyle.go

@@ -28,6 +28,8 @@ import "strings"
 //   - linkcolor: colour of internal links (\hyperlink).
 //   - urlcolor:  colour of \url and \href.
 //   - allcolors: sets both link and url colours at once.
+//   - pdftitle / pdfauthor: the PDF /Info document title and author (see
+//     pdfdriver.go); a non-ASCII value reaches the PDF as UTF-16BE.
 func (e *Engine) applyHypersetup(opts string) {
 	for _, seg := range splitKVSegments(opts, ',') {
 		key, val, has := cutKeyVal(seg)
@@ -41,6 +43,10 @@ func (e *Engine) applyHypersetup(opts string) {
 		case "allcolors", "allcolours":
 			c := e.resolveColor(val)
 			e.hyperLinkColor, e.hyperURLColor = c, c
+		case "pdftitle":
+			e.pdfTitle = val
+		case "pdfauthor":
+			e.pdfAuthor = val
 		}
 	}
 }

pdfdriver.go

@@ -33,7 +33,12 @@ func (e *Engine) RenderPDF(w io.Writer, margin float64) error {
 		return fmt.Errorf("texengine: PDF font load: %w", err)
 	}
 	size := float64(ef.sizePt())
-	doc := pdfkit.New(pdfkit.Options{})
+	// \hypersetup{pdftitle=…,pdfauthor=…} populates the PDF information dictionary,
+	// so a viewer's title bar and document properties — and reference managers —
+	// read the paper's real title and author rather than nothing (see hyperstyle.go).
+	// go-pdfkit encodes a non-ASCII value as a UTF-16BE text string, so an accented
+	// title is correct.
+	doc := pdfkit.New(pdfkit.Options{Title: e.pdfTitle, Author: e.pdfAuthor})
 	vmargin := e.renderVMargin(margin)
 	paperW, paperH, _ := e.paperSizePt()
 	for _, page := range e.Pages() {

pdfinfo_test.go

@@ -0,0 +1,89 @@
+// Copyright (c) the go-tex/engine authors.
+// SPDX-License-Identifier: BSD-3-Clause
+
+package engine
+
+import (
+	"bytes"
+	"strings"
+	"testing"
+)
+
+// renderPDFDoc runs a small document to PDF and returns the raw bytes as a string.
+// The information dictionary (/Title, /Author) is not stream-compressed, so a test
+// can grep the raw PDF for it.
+func renderPDFDoc(t *testing.T, body string) string {
+	t.Helper()
+	fp := pdfFontOrSkip(t)
+	e := New()
+	e.LoadLaTeX()
+	e.Run(`\font\rm={` + fp + `} at 12pt \rm`)
+	if _, err := e.Run(`\documentclass{article}\begin{document}` + body + `\end{document}`); err != nil {
+		t.Fatal(err)
+	}
+	var buf bytes.Buffer
+	if err := e.RenderPDF(&buf, 24); err != nil {
+		t.Fatalf("RenderPDF: %v", err)
+	}
+	return buf.String()
+}
+
+// \hypersetup{pdftitle=…,pdfauthor=…} reaches the PDF information dictionary.
+func TestPDFInfoTitleAndAuthor(t *testing.T) {
+	out := renderPDFDoc(t, `\hypersetup{pdftitle={A Study of Widgets},pdfauthor={Ada Lovelace}}Body.`)
+	if !strings.Contains(out, `/Title (A Study of Widgets)`) {
+		t.Errorf("pdftitle did not reach /Info /Title")
+	}
+	if !strings.Contains(out, `/Author (Ada Lovelace)`) {
+		t.Errorf("pdfauthor did not reach /Info /Author")
+	}
+}
+
+// An accented pdftitle is written UTF-16BE, not as raw UTF-8 (the payoff of the
+// go-pdfkit v0.10.0 text-string work).
+func TestPDFInfoAccentedTitleIsUTF16(t *testing.T) {
+	out := renderPDFDoc(t, `\hypersetup{pdftitle={Résumé des travaux}}Body.`)
+	if !strings.Contains(out, "<FEFF") {
+		t.Errorf("accented pdftitle was not written UTF-16BE")
+	}
+	if strings.Contains(out, "Résumé des travaux") {
+		t.Errorf("accented pdftitle leaked into the PDF as raw UTF-8")
+	}
+}
+
+// Without a pdftitle the document has no /Title in its /Info (the pre-existing
+// behaviour is preserved — no empty title is emitted).
+func TestPDFInfoNoTitleByDefault(t *testing.T) {
+	out := renderPDFDoc(t, `Body with no metadata.`)
+	if strings.Contains(out, "/Title") {
+		t.Errorf("a /Title was emitted though no pdftitle was set")
+	}
+}
+
+// The package-option form sets the metadata just as \hypersetup does.
+func TestPDFInfoFromPackageOptions(t *testing.T) {
+	fp := pdfFontOrSkip(t)
+	e := New()
+	e.LoadLaTeX()
+	e.Run(`\font\rm={` + fp + `} at 12pt \rm`)
+	if _, err := e.Run(`\documentclass{article}\usepackage[pdftitle={Wide Paper}]{hyperref}` +
+		`\begin{document}Body.\end{document}`); err != nil {
+		t.Fatal(err)
+	}
+	var buf bytes.Buffer
+	if err := e.RenderPDF(&buf, 24); err != nil {
+		t.Fatalf("RenderPDF: %v", err)
+	}
+	if !strings.Contains(buf.String(), `/Title (Wide Paper)`) {
+		t.Errorf("\\usepackage[pdftitle=…]{hyperref} did not set /Title")
+	}
+}
+
+// The parsed values are stored on the engine (a unit check independent of a font).
+func TestPDFInfoStoredOnEngine(t *testing.T) {
+	e := New()
+	e.applyHypersetup(`pdftitle={My Title}, pdfauthor={Me}`)
+	if e.pdfTitle != "My Title" || e.pdfAuthor != "Me" {
+		t.Errorf("stored title=%q author=%q, want (My Title, Me)", e.pdfTitle, e.pdfAuthor)
+	}
+}