calculate sleep time for slideshow interval more accurately

internal/slideshow/slideshow.go

@@ -21,9 +21,10 @@ var previousImage string
 func Start() {
 	loggo.Info("starting the image slideshow...", "interval: "+strconv.FormatFloat(config.Interval.Seconds(), 'f', 0, 64)+" seconds")
 	var sleepTime time.Duration
-	var scaleTime time.Duration
+	var loopTime time.Duration
 	scaleImages := config.IsResolutionSet()
 	for {
+		loopTimestamp := time.Now()
 		var image string
 		var palette []color.Color
 		var data []byte
@@ -34,18 +35,17 @@ func Start() {
 			}
 		}
 		if scaleImages {
-			scaleTimestamp := time.Now()
 			tmp, error := scale(image)
 			if error != nil {
 				loggo.Error("encountered an error scaling an image", "image: "+image, error.Error())
 				continue
 			}
 			data = tmp
-			scaleTime = time.Since(scaleTimestamp)
 			palette, _ = getColorPaletteRaw(data)
 		} else {
 			palette, _ = getColorPalette(image)
 		}
+		loopTime = time.Since(loopTimestamp)
 		if sleepTime > 0 {
 			loggo.Debug("sleeping for " + strconv.FormatInt(sleepTime.Milliseconds(), 10) + "ms before next image will be displayed...")
 			time.Sleep(sleepTime)
@@ -64,7 +64,7 @@ func Start() {
 			}
 			loggo.Info("set new background image", "image: "+image)
 		}
-		sleepTime = config.Interval - scaleTime
+		sleepTime = config.Interval - loopTime
 	}
 }