added random wallpaper

.config/systemd/user/randomwallpaper.service

@@ -0,0 +1,6 @@
+[Unit]
+Description=set wallpapers to random ones
+
+[Service]
+Type=oneshot
+ExecStart=/bin/bash -c '${HOME}/.local/bin/randomwallpaper'

.config/systemd/user/randomwallpaper.timer

@@ -0,0 +1,10 @@
+[Unit]
+Description=Change the wallpaper ever half hour
+
+[Timer]
+OnBootSec=1min
+OnUnitActiveSec=30min
+
+[Install]
+WantedBy=timers.target
+

scripts/randomwallpaper.c

@@ -0,0 +1,52 @@
+// clang -lX11 -lXinerama randomwallpaper.c -o ~/.local/bin/randomwallpaper
+// this script updates the desktop wallpapers using the nitrogen tool to random
+// wallpapers on all displays.
+#include <X11/Xlib.h>
+#include <X11/extensions/Xinerama.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+void update_wallpapers(Display *d);
+
+int main(int argc, char *argv[]) {
+  Display *d = XOpenDisplay(NULL);
+
+  if (d) {
+    int dummy1, dummy2;
+
+    // check if xinerama is supported and enabled
+    if (XineramaQueryExtension(d, &dummy1, &dummy2) && XineramaIsActive(d)) {
+      update_wallpapers(d);
+    } else {
+      puts("No Xinerama!\n");
+      XCloseDisplay(d);
+      return 1;
+    }
+
+    XCloseDisplay(d);
+    return 0;
+  } else {
+    puts("Couldn't open display!\n");
+    // I return with 0 here, as I don't really wanna see it as an error if this
+    // script is run without an X server running.
+    return 0;
+  }
+}
+
+void update_wallpapers(Display *d) {
+  int heads = 0;
+  XineramaScreenInfo *info = XineramaQueryScreens(d, &heads);
+
+  if (heads > 0) {
+    for (int i = 0; i < heads; i++) {
+      // works as long as the user doesn't have over 999 monitors :P
+      char command[40];
+      sprintf(command, "nitrogen --random --set-zoom --head=%d", i);
+      printf("Setting wallpaper for screen %d with size %dx%d\n", i,
+             info[i].width, info[i].height);
+      system(command);
+    }
+  }
+
+  XFree(info);
+}