Add FontFileNamer type, set default fontNamer.

font.go

@@ -13,8 +13,9 @@ import (
 )
 
 var (
-	fontFolder = "../resource/font/"
-	fonts      = make(map[string]*truetype.Font)
+	fontFolder               = "../resource/font/"
+	fonts                    = make(map[string]*truetype.Font)
+	fontNamer  FontFileNamer = FontFileName
 )
 
 type FontStyle byte
@@ -39,6 +40,8 @@ type FontData struct {
 	Style  FontStyle
 }
 
+type FontFileNamer func(fontData FontData) string
+
 func FontFileName(fontData FontData) string {
 	fontFileName := fontData.Name
 	switch fontData.Family {