Add SetFontLoader() method to load fonts from arbitrary locations

2 files changed, 46 insertions, 2 deletions

diff --git a/def.go b/def.go
index df21e05..33eca47 100644
--- a/def.go
+++ b/def.go
@@ -18,6 +18,7 @@ package gofpdf
 
 import (
 	"bytes"
+	"io"
 )
 
 // Version of FPDF from which this package is derived
@@ -132,6 +133,15 @@ type InitType struct {
 	FontDirStr     string
 }
 
+// FontLoader is used to read fonts (JSON font specification and zlib compressed font binaries)
+// from arbitrary locations (e.g. files, zip files, embedded font resources).
+//
+// Open provides an io.Reader for the specified font file (.json or .z). The file name
+// does never include a path. Open returns an error if the specified file cannot be opened.
+type FontLoader interface {
+	Open(name string) (io.Reader, error)
+}
+
 // Fpdf is the principal structure for creating a single PDF document
 type Fpdf struct {
 	page             int                       // current page number
@@ -160,6 +170,7 @@ type Fpdf struct {
 	lasth            float64                   // height of last printed cell
 	lineWidth        float64                   // line width in user unit
 	fontpath         string                    // path containing fonts
+	fontLoader       FontLoader                // used to load font files from arbitrary locations
 	coreFonts        map[string]bool           // array of core font names
 	fonts            map[string]fontDefType    // array of used fonts
 	fontFiles        map[string]fontFileType   // array of font files
diff --git a/fpdf.go b/fpdf.go
index 1508548..b2872e6 100644
--- a/fpdf.go
+++ b/fpdf.go
@@ -313,6 +313,14 @@ func (f *Fpdf) SetFontLocation(fontDirStr string) {
 	f.fontpath = fontDirStr
 }
 
+// SetFontLoader sets a loader used to load font files (.json and .z) from
+// arbitrary locations. If a font loader has been specified, Fpdf first tries
+// to load files using the font loader. If the loading files Fpdf tries to
+// load the font from the configured fonts directory (see SetFontLocation).
+func (f *Fpdf) SetFontLoader(loader FontLoader) {
+	f.fontLoader = loader
+}
+
 // SetHeaderFunc sets the function that lets the application render the page
 // header. The specified function is automatically called by AddPage() and
 // should not be called directly by the application. The implementation in Fpdf
@@ -1358,8 +1366,19 @@ func (f *Fpdf) AddFont(familyStr, styleStr, fileStr string) {
 	if fileStr == "" {
 		fileStr = strings.Replace(familyStr, " ", "", -1) + strings.ToLower(styleStr) + ".json"
 	}
-	fileStr = path.Join(f.fontpath, fileStr)
 
+	if f.fontLoader != nil {
+		reader, err := f.fontLoader.Open(fileStr)
+		if err == nil {
+			f.AddFontFromReader(familyStr, styleStr, reader)
+			if closer, ok := reader.(io.Closer); ok {
+				closer.Close()
+			}
+			return
+		}
+	}
+
+	fileStr = path.Join(f.fontpath, fileStr)
 	file, err := os.Open(fileStr)
 	if err != nil {
 		f.err = err
@@ -2971,7 +2990,7 @@ func (f *Fpdf) putfonts() {
 		f.newobj()
 		info.n = f.n
 		f.fontFiles[file] = info
-		font, err := ioutil.ReadFile(path.Join(f.fontpath, file))
+		font, err := f.loadFontFile(file)
 		if err != nil {
 			f.err = err
 			return
@@ -3071,6 +3090,20 @@ func (f *Fpdf) putfonts() {
 	return
 }
 
+func (f *Fpdf) loadFontFile(name string) ([]byte, error) {
+	if f.fontLoader != nil {
+		reader, err := f.fontLoader.Open(name)
+		if err == nil {
+			data, err := ioutil.ReadAll(reader)
+			if closer, ok := reader.(io.Closer); ok {
+				closer.Close()
+			}
+			return data, err
+		}
+	}
+	return ioutil.ReadFile(path.Join(f.fontpath, name))
+}
+
 func (f *Fpdf) putimages() {
 	for _, img := range f.images {
 		f.putimage(img)