Lazy load fonts (#704)

Co-authored-by: Mark Spicer <mark@tidbyt.com>

render/fonts.go

@@ -10,22 +10,36 @@ import (
 	"golang.org/x/image/font"
 )
 
-var Font = map[string]font.Face{}
-
-func init() {
-	for name, dataB64 := range FontDataRaw {
-		data, err := base64.StdEncoding.DecodeString(dataB64)
-		if err != nil {
-			log.Printf("couldn't decode %s: %s", name, err)
-			continue
-		}
-
-		f, err := bdf.Parse(data)
-		if err != nil {
-			log.Printf("couldn't parse %s: %s", name, err)
-			continue
-		}
-
-		Font[name] = f.NewFace()
+var fontCache = map[string]font.Face{}
+
+func GetFontList() []string {
+	fontNames := []string{}
+	for key := range fontDataRaw {
+		fontNames = append(fontNames, key)
+	}
+	return fontNames
+}
+
+func GetFont(name string) font.Face {
+	if font, ok := fontCache[name]; ok {
+		return font
+	}
+
+	dataB64, ok := fontDataRaw[name]
+	if !ok {
+		log.Panicf("Unknown font '%s', the available fonts are: %v", name, GetFontList())
 	}
+
+	data, err := base64.StdEncoding.DecodeString(dataB64)
+	if err != nil {
+		log.Panicf("couldn't decode %s: %s", name, err)
+	}
+
+	f, err := bdf.Parse(data)
+	if err != nil {
+		log.Panicf("couldn't parse %s: %s", name, err)
+	}
+
+	fontCache[name] = f.NewFace()
+	return fontCache[name]
 }

render/gen/embedfonts.go

@@ -21,7 +21,7 @@ const fontsTemplate = `// Code generated by embedfonts.go, DO NOT EDIT.
 
 package render
 
-var FontDataRaw = map[string]string{
+var fontDataRaw = map[string]string{
 {{range .}} "{{.Name}}": "{{.DataB64}}",
 {{end}}
 }

render/text.go

@@ -54,10 +54,10 @@ func (t *Text) PaintBounds(bounds image.Rectangle, frameIdx int) image.Rectangle
 }
 
 func (t *Text) Init() error {
-	face := Font[DefaultFontFace]
-	if t.Font != "" {
-		face = Font[t.Font]
+	if t.Font == "" {
+		t.Font = DefaultFontFace
 	}
+	face := GetFont(t.Font)
 
 	dc := gg.NewContext(0, 0)
 	dc.SetFontFace(face)

render/wrappedtext.go

@@ -45,10 +45,10 @@ type WrappedText struct {
 }
 
 func (tw WrappedText) PaintBounds(bounds image.Rectangle, frameIdx int) image.Rectangle {
-	face := Font[DefaultFontFace]
-	if tw.Font != "" {
-		face = Font[tw.Font]
+	if tw.Font == "" {
+		tw.Font = DefaultFontFace
 	}
+	face := GetFont(tw.Font)
 	// The bounds provided by user or parent widget
 	width := tw.Width
 	if width == 0 {
@@ -99,10 +99,10 @@ func (tw WrappedText) PaintBounds(bounds image.Rectangle, frameIdx int) image.Re
 }
 
 func (tw WrappedText) Paint(dc *gg.Context, bounds image.Rectangle, frameIdx int) {
-	face := Font[DefaultFontFace]
-	if tw.Font != "" {
-		face = Font[tw.Font]
+	if tw.Font == "" {
+		tw.Font = DefaultFontFace
 	}
+	face := GetFont(tw.Font)
 	// Text alignment
 	align := gg.AlignLeft
 	if tw.Align == "center" {