fixed .gitignore

.gitignore

@@ -1,2 +1,2 @@
-slideshow
+./slideshow
 __debug_bin*

internal/slideshow/scale.go

@@ -0,0 +1,47 @@
+package slideshow
+
+import (
+	"errors"
+	"io"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"strconv"
+	"strings"
+	"time"
+
+	"git.velvettear.de/velvettear/loggo"
+	"git.velvettear.de/velvettear/slideshow/internal/config"
+)
+
+// scale an image
+func scale(image string) (string, error) {
+	timestamp := time.Now().UnixMilli()
+	scaledImage := filepath.Join(os.TempDir(), strconv.FormatInt(timestamp, 10)+"_"+filepath.Base(image))
+	arguments := []string{image, "-resize", config.Resolution + "^", "-gravity", "center", "-extent", config.Resolution, scaledImage}
+	cmd := exec.Command("convert", arguments...)
+	stdout, stdoutError := cmd.StdoutPipe()
+	stderr, stderrError := cmd.StderrPipe()
+	cmd.Start()
+	if stdoutError != nil {
+		return scaledImage, stdoutError
+	}
+	if stderrError != nil {
+		return scaledImage, stdoutError
+	}
+	_, stdoutError = io.ReadAll(stdout)
+	if stdoutError != nil {
+		return scaledImage, stdoutError
+	}
+	errorBytes, stderrError := io.ReadAll(stderr)
+	if stderrError != nil {
+		return scaledImage, stdoutError
+	}
+	cmd.Wait()
+	errorMessage := strings.TrimSpace(string(errorBytes))
+	if len(errorMessage) > 0 {
+		return scaledImage, errors.New(errorMessage)
+	}
+	loggo.DebugTimed("successfully scaled image", timestamp, "image: "+image, "scaled image: "+scaledImage, "resolution: "+config.Resolution)
+	return scaledImage, nil
+}

internal/slideshow/slideshow.go

@@ -0,0 +1,81 @@
+package slideshow
+
+import (
+	"errors"
+	"io"
+	"os"
+	"os/exec"
+	"strconv"
+	"strings"
+	"time"
+
+	"git.velvettear.de/velvettear/loggo"
+	"git.velvettear.de/velvettear/slideshow/internal/config"
+	"git.velvettear.de/velvettear/slideshow/internal/watcher"
+)
+
+// internal counter
+var counter int64
+
+// start the slideshow
+func Start() {
+	loggo.Info("starting the image slideshow...", "interval: "+strconv.FormatFloat(config.Interval.Seconds(), 'f', 0, 64)+" seconds")
+	for {
+		var sleepTime time.Duration
+		if counter > 0 {
+			sleepTime = time.Until(time.Now().Add(config.Interval))
+		}
+		var scaledImage string
+		image := watcher.GetRandomImage()
+		if len(config.Resolution) > 0 {
+			tmp, error := scale(image)
+			if error != nil {
+				loggo.Fatal("encountered an error scaling an image", "image: "+image, error.Error())
+			}
+			scaledImage = tmp
+		}
+		if sleepTime > 0 {
+			time.Sleep(sleepTime)
+		}
+		error := setBackground(image)
+		if error != nil {
+			loggo.Error("encountered an error setting the background image", "image: "+image, error.Error())
+		}
+		counter++
+		loggo.Info("set new background image", "image: "+image)
+		if len(scaledImage) > 0 {
+			error = os.Remove(image)
+			if error != nil {
+				loggo.Error("encountered an error deleting a scaled image", "image: "+scaledImage)
+			}
+		}
+	}
+}
+
+// set the background image via 'feh'
+func setBackground(image string) error {
+	cmd := exec.Command("feh", "--no-fehbg", "--bg-fill", image)
+	stdout, stdoutError := cmd.StdoutPipe()
+	stderr, stderrError := cmd.StderrPipe()
+	cmd.Start()
+	if stdoutError != nil {
+		return stdoutError
+	}
+	if stderrError != nil {
+		return stderrError
+	}
+	_, stdoutError = io.ReadAll(stdout)
+	if stdoutError != nil {
+		return stdoutError
+	}
+	errorBytes, stderrError := io.ReadAll(stderr)
+	if stderrError != nil {
+		return stderrError
+	}
+	cmd.Wait()
+	error := strings.TrimSpace(string(errorBytes))
+	if len(error) > 0 {
+		return errors.New(error)
+	}
+	return nil
+}