add systemd support (#1253)

* add systemd support
motivation for this is is proper ordering of related/bound/required
services to Hyprland (e.g. swaybg) that would need to have a compositor
ready.

this could possibly be a build-time option of course.

see also:
example/ files for example of services

Signed-off-by: Paymon MARANDI <darwinskernel@gmail.com>

* nix: add withSystemd flag

Signed-off-by: Paymon MARANDI <darwinskernel@gmail.com>
Co-authored-by: Mihai Fufezan <fufexan@protonmail.com>
Co-authored-by: Vaxerski <vaxry@vaxry.net>

src/main.cpp

@@ -4,6 +4,9 @@
 #include "config/ConfigManager.hpp"
 #include "init/initHelpers.hpp"
 #include <iostream>
+#ifdef USES_SYSTEMD
+#include <systemd/sd-daemon.h> // for sd_notify
+#endif
 
 int main(int argc, char** argv) {
 
@@ -66,6 +69,12 @@ int main(int argc, char** argv) {
     // If we are here it means we got yote.
     Debug::log(LOG, "Hyprland reached the end.");
 
+#ifdef USES_SYSTEMD
+    // tell systemd it destroy bound/related units
+    if (sd_booted() > 0)
+       sd_notify(0, "STOPPING=1");
+#endif
+
     wl_display_destroy_clients(g_pCompositor->m_sWLDisplay);
 
     // kill all clients