add ability to configure language in config file

backend/config.go

@@ -48,7 +48,8 @@ type AppConfig struct {
 	ShowTrackChangeNotification bool
 	EnableLrcLib                bool
 	SkipSSLVerify               bool
-	EnqueueBatchSize 	    int
+	EnqueueBatchSize            int
+	Language                    string
 
 	// Experimental - may be removed in future
 	FontNormalTTF string
@@ -174,7 +175,8 @@ func DefaultConfig(appVersionTag string) *Config {
 			ShowTrackChangeNotification: false,
 			EnableLrcLib:                true,
 			SkipSSLVerify:               false,
-			EnqueueBatchSize:	     100,
+			EnqueueBatchSize:            100,
+			Language:                    "auto",
 		},
 		AlbumPage: AlbumPageConfig{
 			TracklistColumns: []string{"Artist", "Time", "Plays", "Favorite", "Rating"},

main.go

@@ -6,6 +6,7 @@ import (
 	"log"
 	"os"
 	"runtime"
+	"slices"
 	"sync"
 	"time"
 
@@ -46,7 +47,26 @@ func main() {
 		os.Setenv("FYNE_SCALE", "1.1")
 	}
 
-	lang.AddTranslationsFS(res.Translations, "translations")
+	// load configured app language, or all otherwise
+	lIdx := slices.IndexFunc(res.TranslationsInfo, func(t res.TranslationInfo) bool {
+		return t.Name == myApp.Config.Application.Language
+	})
+	success := false
+	if lIdx > 0 {
+		tr := res.TranslationsInfo[lIdx]
+		content, err := res.Translations.ReadFile("translations/" + tr.TranslationFileName)
+		if err == nil {
+			// "trick" Fyne into loading translations for configured language
+			// by pretending it's the translation for the system locale
+			name := lang.SystemLocale().LanguageString()
+			lang.AddTranslations(fyne.NewStaticResource(name+".json", content))
+			success = true
+		}
+	}
+	if !success {
+		lang.AddTranslationsFS(res.Translations, "translations")
+	}
+
 	fyneApp := app.New()
 	fyneApp.SetIcon(res.ResAppicon256Png)
 

res/translations.go

@@ -4,3 +4,23 @@ import "embed"
 
 //go:embed translations
 var Translations embed.FS
+
+type TranslationInfo struct {
+	Name                string
+	DisplayName         string
+	TranslationFileName string
+}
+
+var TranslationsInfo = []TranslationInfo{
+	{Name: "de", DisplayName: "Deutsch", TranslationFileName: "de.json"},
+	{Name: "en", DisplayName: "English", TranslationFileName: "en.json"},
+	{Name: "es", DisplayName: "Español", TranslationFileName: "es.json"},
+	{Name: "fr", DisplayName: "François", TranslationFileName: "fr.json"},
+	{Name: "it", DisplayName: "Italiano", TranslationFileName: "it.json"},
+	{Name: "ja", DisplayName: "日本語", TranslationFileName: "de.json"},
+	{Name: "pl", DisplayName: "Polski", TranslationFileName: "pl.json"},
+	{Name: "pt_BR", DisplayName: "Português (BR)", TranslationFileName: "pt_BR.json"},
+	{Name: "ro", DisplayName: "Română", TranslationFileName: "ro"},
+	{Name: "zhHans", DisplayName: "中文", TranslationFileName: "zhHans.json"},
+	{Name: "zhHant", DisplayName: "中文 (trad.)", TranslationFileName: "zhHant.json"},
+}