fix #1: add cache of latest command to not run wallpaper update when it's already up to date

callback.go

@@ -5,7 +5,7 @@ import (
 	"os/exec"
 )
 
-func CallbackUpdateWallpapers(callback string, files, screens []string) (*exec.Cmd, error) {
+func CallbackUpdateWallpapers(callback string, files, screens []string) *exec.Cmd {
 	args := []string{}
 
 	for key, file := range files {
@@ -15,5 +15,5 @@ func CallbackUpdateWallpapers(callback string, files, screens []string) (*exec.C
 	cmd := exec.Command(callback, args...)
 	cmd.Env = os.Environ()
 
-	return cmd, cmd.Run()
+	return cmd
 }

feh.go

@@ -5,7 +5,7 @@ import (
 	"os/exec"
 )
 
-func FehUpdateWallpapers(files []string) (*exec.Cmd, error) {
+func FehUpdateWallpapers(files []string) *exec.Cmd {
 	args := []string{}
 
 	for _, file := range files {
@@ -15,5 +15,5 @@ func FehUpdateWallpapers(files []string) (*exec.Cmd, error) {
 	cmd := exec.Command("feh", args...)
 	cmd.Env = os.Environ()
 
-	return cmd, cmd.Run()
+	return cmd
 }

main.go

@@ -16,18 +16,21 @@ func main() {
 	}
 
 	config, err := LoadConfiguration(os.Args[1])
+
 	if err != nil {
 		log.Printf("[ERROR] %s", err.Error())
 		os.Exit(1)
 	}
 
-	UpdateWallapers(config)
+	var lastCommand string
+
+	UpdateWallapers(config, &lastCommand)
 
 	for recv.Next() {
 		event := recv.Event().(*i3.WorkspaceEvent)
 
 		if event.Change == "focus" {
-			UpdateWallapers(config)
+			UpdateWallapers(config, &lastCommand)
 		}
 	}
 }

wallpaper.go

@@ -40,7 +40,7 @@ func GetOutputsWallpapers(config Config) ([]string, []string, error) {
 	return files, screens, nil
 }
 
-func UpdateWallapers(config Config) {
+func UpdateWallapers(config Config, lastCommand *string) {
 	files, screens, err := GetOutputsWallpapers(config)
 	if err != nil {
 		log.Printf("[ERROR] %s", err.Error())
@@ -50,14 +50,22 @@ func UpdateWallapers(config Config) {
 	var cmd *exec.Cmd
 
 	if config.Callback == "" {
-		cmd, err = FehUpdateWallpapers(files)
+		cmd = FehUpdateWallpapers(files)
 	} else {
-		cmd, err = CallbackUpdateWallpapers(config.Callback, files, screens)
+		cmd = CallbackUpdateWallpapers(config.Callback, files, screens)
 	}
 
+	if cmd.String() == *lastCommand {
+		log.Printf("[INFO] wallapaper(s) already up to date")
+		return
+	}
+
+	err = cmd.Run()
+
 	if err != nil {
 		log.Printf("[ERROR] cmd=%s error=%s", cmd.String(), err.Error())
 	} else {
 		log.Printf("[SUCCESS] cmd=%s", cmd.String())
+		*lastCommand = cmd.String()
 	}
 }