Support UTF-8 aliases and correct problem with UTF-8 page count alias

fpdf.go

@@ -3782,17 +3782,28 @@ func (f *Fpdf) SetJavascript(script string) {
 // replace all occurrences of that alias after writing but before the
 // document is closed.
 func (f *Fpdf) RegisterAlias(alias, replacement string) {
+	// Note: map[string]string assignments embed literal escape ("\00") sequences
+	// into utf16 key and value strings. Consequently, subsequent search/replace
+	// operations will fail unexpectedly if utf8toutf16() conversions take place
+	// here. Instead, conversions are deferred until the actual search/replace
+	// operation takes place when the PDF output is generated.
 	f.aliasMap[alias] = replacement
 }
 
 func (f *Fpdf) replaceAliases() {
-	for alias, replacement := range f.aliasMap {
-		for n := 1; n <= f.page; n++ {
-			s := f.pages[n].String()
-			if strings.Contains(s, alias) {
-				s = strings.Replace(s, alias, replacement, -1)
-				f.pages[n].Truncate(0)
-				f.pages[n].WriteString(s)
+	for mode := 0; mode < 2; mode++ {
+		for alias, replacement := range f.aliasMap {
+			if mode == 1 {
+				alias = utf8toutf16(alias, false)
+				replacement = utf8toutf16(replacement, false)
+			}
+			for n := 1; n <= f.page; n++ {
+				s := f.pages[n].String()
+				if strings.Contains(s, alias) {
+					s = strings.Replace(s, alias, replacement, -1)
+					f.pages[n].Truncate(0)
+					f.pages[n].WriteString(s)
+				}
 			}
 		}
 	}
@@ -3801,14 +3812,10 @@ func (f *Fpdf) replaceAliases() {
 func (f *Fpdf) putpages() {
 	var wPt, hPt float64
 	var pageSize SizeType
-	// var linkList []linkType
 	var ok bool
 	nb := f.page
 	if len(f.aliasNbPagesStr) > 0 {
 		// Replace number of pages
-		alias := utf8toutf16(f.aliasNbPagesStr, false)
-		r := utf8toutf16(sprintf("%d", nb), false)
-		f.RegisterAlias(alias, r)
 		f.RegisterAlias(f.aliasNbPagesStr, sprintf("%d", nb))
 	}
 	f.replaceAliases()

fpdf_test.go

@@ -2246,13 +2246,14 @@ func ExampleFpdf_AddSpotColor() {
 func ExampleFpdf_RegisterAlias() {
 	pdf := gofpdf.New("P", "mm", "A4", "")
 	pdf.SetFont("Arial", "", 12)
+	pdf.AliasNbPages("")
 	pdf.AddPage()
 
 	// Write the table of contents. We use aliases instead of the page number
 	// because we don't know which page the section will begin on.
 	numSections := 3
 	for i := 1; i <= numSections; i++ {
-		pdf.Cell(0, 10, fmt.Sprintf("Section %d begins on page {%d}", i, i))
+		pdf.Cell(0, 10, fmt.Sprintf("Section %d begins on page {mark %d}", i, i))
 		pdf.Ln(10)
 	}
 
@@ -2261,8 +2262,8 @@ func ExampleFpdf_RegisterAlias() {
 	// by the current page number.
 	for i := 1; i <= numSections; i++ {
 		pdf.AddPage()
-		pdf.RegisterAlias(fmt.Sprintf("{%d}", i), fmt.Sprintf("%d", pdf.PageNo()))
-		pdf.Write(10, fmt.Sprintf("Section %d", i))
+		pdf.RegisterAlias(fmt.Sprintf("{mark %d}", i), fmt.Sprintf("%d", pdf.PageNo()))
+		pdf.Write(10, fmt.Sprintf("Section %d, page %d of {nb}", i, pdf.PageNo()))
 	}
 
 	fileStr := example.Filename("Fpdf_RegisterAlias")
@@ -2272,6 +2273,40 @@ func ExampleFpdf_RegisterAlias() {
 	// Successfully generated pdf/Fpdf_RegisterAlias.pdf
 }
 
+// ExampleFpdf_RegisterAliasUTF8 demonstrates how to use `RegisterAlias` to
+// create a table of contents. This particular example demonstrates the use of
+// UTF-8 aliases.
+func ExampleFpdf_RegisterAliasUTF8() {
+	pdf := gofpdf.New("P", "mm", "A4", "")
+	pdf.AddUTF8Font("dejavu", "", example.FontFile("DejaVuSansCondensed.ttf"))
+	pdf.SetFont("dejavu", "", 12)
+	pdf.AliasNbPages("{entute}")
+	pdf.AddPage()
+
+	// Write the table of contents. We use aliases instead of the page number
+	// because we don't know which page the section will begin on.
+	numSections := 3
+	for i := 1; i <= numSections; i++ {
+		pdf.Cell(0, 10, fmt.Sprintf("Sekcio %d komenciĝas ĉe paĝo {ĉi tiu marko %d}", i, i))
+		pdf.Ln(10)
+	}
+
+	// Write the sections. Before we start writing, we use `RegisterAlias` to
+	// ensure that the alias written in the table of contents will be replaced
+	// by the current page number.
+	for i := 1; i <= numSections; i++ {
+		pdf.AddPage()
+		pdf.RegisterAlias(fmt.Sprintf("{ĉi tiu marko %d}", i), fmt.Sprintf("%d", pdf.PageNo()))
+		pdf.Write(10, fmt.Sprintf("Sekcio %d, paĝo %d de {entute}", i, pdf.PageNo()))
+	}
+
+	fileStr := example.Filename("Fpdf_RegisterAliasUTF8")
+	err := pdf.OutputFileAndClose(fileStr)
+	example.Summary(err, fileStr)
+	// Output:
+	// Successfully generated pdf/Fpdf_RegisterAliasUTF8.pdf
+}
+
 // ExampleNewGrid demonstrates the generation of graph grids.
 func ExampleNewGrid() {
 	pdf := gofpdf.New("P", "mm", "A4", "")