feat: add Hyprpaper backend

Hyprpaper is designed primarily for Hyprland but works for all wlroots based compositors. It runs as a daemon and is controlled via a socket, which prevents flashes during the transition between images.

The Hyprpaper backend is placed first in the order of possible backends but will only be chosen if it is already running.

Only two modes are supported, cover (the default) and contain, so all other modes are mapped to one of the two.

Due to a bug in Hyprpaper, the latest release (v0.6.0) is not compatible because it does not support wildcard display selection. Until a new release is published, only builds directly from Git will work correctly.

backend.go

@@ -6,6 +6,7 @@ package wallutils
 // WMs contains all available backends for changing the wallpaper
 // Some backends may require cgo (sway + x11)
 var WMs = []WM{
+	&Hyprpaper{},
 	&Sway{},
 	&Deepin{},
 	&Xfce4{},

backend_nocgo.go

@@ -6,6 +6,7 @@ package wallutils
 // WMs contains all available backends for changing the wallpaper
 // Only backends that do not require cgo should be included here.
 var WMs = []WM{
+	&Hyprpaper{},
 	//&Sway{},
 	&Deepin{},
 	&Xfce4{},

hyprpaper.go

@@ -0,0 +1,114 @@
+package wallutils
+
+import (
+	"fmt"
+	"net"
+	"path"
+
+	"github.com/xyproto/env/v2"
+)
+
+// Hyprpaper compatible windowmanager
+type Hyprpaper struct {
+	mode    string
+	verbose bool
+	sock    string
+}
+
+// Name returns the name of this window manager or desktop environment
+func (sb *Hyprpaper) Name() string {
+	return "Hyprpaper"
+}
+
+// ExecutablesExists checks if executables associated with this backend exists in the PATH
+func (sb *Hyprpaper) ExecutablesExists() bool {
+	return which("hyprpaper") != ""
+}
+
+// Running examines environment variables to try to figure out if this backend is currently running
+func (sb *Hyprpaper) Running() bool {
+	inst := env.Str("HYPRLAND_INSTANCE_SIGNATURE")
+	sb.sock = path.Join("/tmp/hypr", inst, ".hyprpaper.sock")
+	return exists(sb.sock)
+}
+
+// SetMode will set the current way to display the wallpaper (stretched, tiled etc)
+func (sb *Hyprpaper) SetMode(mode string) {
+	sb.mode = mode
+}
+
+// SetVerbose can be used for setting the verbose field to true or false.
+// This will cause this backend to output information about what is is doing on stdout.
+func (sb *Hyprpaper) SetVerbose(verbose bool) {
+	sb.verbose = verbose
+}
+
+// SetWallpaper sets the desktop wallpaper, given an image filename.
+// The image must exist and be readable.
+func (sb *Hyprpaper) SetWallpaper(imageFilename string) error {
+	if !exists(imageFilename) {
+		return fmt.Errorf("no such file: %s", imageFilename)
+	}
+
+	// Connect to the Hyprpaper socket
+	sock, err := net.DialUnix("unix", nil, &net.UnixAddr{Name: sb.sock, Net: "unix"})
+
+	if err != nil {
+		return err
+	}
+
+	defer sock.Close()
+
+	// Preload the image
+	if err = runHyprCmd(sock, "preload "+imageFilename); err != nil {
+		return err
+	}
+
+	// Set the wallpaper mode
+	mode := defaultMode
+	if sb.mode != "" {
+		mode = sb.mode
+	}
+
+	switch mode {
+	case "center", "tile", "fill", "stretch", "scale", "scaled", "zoom", "zoomed", "stretched":
+		mode = ""
+	case "fit":
+		mode = "contain:"
+	default:
+		// Invalid and unrecognized desktop wallpaper mode
+		return fmt.Errorf("invalid desktop wallpaper mode for swaybg: %s", mode)
+	}
+
+	// Set the wallpaper
+	if err = runHyprCmd(sock, "wallpaper ,"+mode+imageFilename); err != nil {
+		return err
+	}
+
+	// Unload unused images
+	return runHyprCmd(sock, "unload unused")
+}
+
+func runHyprCmd(sock *net.UnixConn, cmd string) error {
+	_, err := sock.Write([]byte(cmd))
+
+	if err != nil {
+		return err
+	}
+
+	buf := [32]byte{}
+
+	n, err := sock.Read(buf[:])
+
+	if err != nil {
+		return err
+	}
+
+	res := string(buf[:n])
+
+	if res != "ok" {
+		return fmt.Errorf("cmd %q failed: %s", cmd, res)
+	}
+
+	return nil
+}