Use systemd as a soft dependency

Dunst does not neccessarily need systemd. Dunst gets started primarily
via DBus. The systemd service is useful on systemd init based systems,
but won't have any impact on non-systemd systems.

To make systemd a soft dependency is neccessary, as pkg-config now also
queries the systemd.pc file, which won't exist on non systemd systems.

Makefile

@@ -8,17 +8,30 @@ ifneq ($(wildcard ./.git/.),)
 VERSION := $(shell git describe --tags)
 endif
 
+ifeq (,${SYSTEMD})
+# Check for systemctl to avoid discrepancies on systems, where
+# systemd is installed, but systemd.pc is in another package 
+systemctl := $(shell command -v systemctl >/dev/null && echo systemctl)
+ifeq (systemctl,${systemctl})
+SYSTEMD := 1
+else
+SYSTEMD := 0
+endif
+endif
+
 SERVICEDIR_DBUS ?= $(shell pkg-config dbus-1 --variable=session_bus_services_dir)
 SERVICEDIR_DBUS := ${SERVICEDIR_DBUS}
 ifeq (,${SERVICEDIR_DBUS})
 $(error "Failed to query pkg-config for package 'dbus-1'!")
 endif
 
+ifneq (0,${SYSTEMD})
 SERVICEDIR_SYSTEMD ?= $(shell pkg-config systemd --variable=systemduserunitdir)
 SERVICEDIR_SYSTEMD := ${SERVICEDIR_SYSTEMD}
 ifeq (,${SERVICEDIR_SYSTEMD})
 $(error "Failed to query pkg-config for package 'systemd'!")
 endif
+endif
 
 LIBS := $(shell pkg-config --libs   ${pkg_config_packs})
 INCS := $(shell pkg-config --cflags ${pkg_config_packs})
@@ -78,10 +91,15 @@ doc: docs/dunst.1
 docs/dunst.1: docs/dunst.pod
 	pod2man --name=dunst -c "Dunst Reference" --section=1 --release=${VERSION} $< > $@
 
-.PHONY: service
+.PHONY: service service-dbus service-systemd
-service:
+service: service-dbus
+service-dbus:
 	@sed "s|##PREFIX##|$(PREFIX)|" org.knopwob.dunst.service.in > org.knopwob.dunst.service
+ifneq (0,${SYSTEMD})
+service: service-systemd
+service-systemd:
 	@sed "s|##PREFIX##|$(PREFIX)|" dunst.systemd.service.in > dunst.systemd.service
+endif
 
 .PHONY: clean clean-dunst clean-dunstify clean-doc clean-tests
 clean: clean-dunst clean-dunstify clean-doc clean-tests
@@ -101,7 +119,10 @@ clean-doc:
 clean-tests:
 	rm -f test/test test/*.o
 
-.PHONY: install install-dunst install-doc install-service uninstall
+.PHONY: install install-dunst install-doc \
+        install-service install-service-dbus install-service-systemd \
+        uninstall \
+        uninstall-service uninstall-service-dbus uninstall-service-systemd
 install: install-dunst install-doc install-service
 
 install-dunst: dunst doc
@@ -114,13 +135,26 @@ install-doc:
 	mkdir -p ${DESTDIR}${PREFIX}/share/dunst
 	install -m644 dunstrc ${DESTDIR}${PREFIX}/share/dunst
 
-install-service: service
+install-service: service install-service-dbus
+install-service-dbus:
 	install -Dm644 org.knopwob.dunst.service ${DESTDIR}${SERVICEDIR_DBUS}/org.knopwob.dunst.service
+ifneq (0,${SYSTEMD})
+install-service: install-service-systemd
+install-service-systemd:
 	install -Dm644 dunst.systemd.service ${DESTDIR}${SERVICEDIR_SYSTEMD}/dunst.service
+endif
 
-uninstall:
+uninstall: uninstall-service
 	rm -f ${DESTDIR}${PREFIX}/bin/dunst
 	rm -f ${DESTDIR}${MANPREFIX}/man1/dunst.1
-	rm -f ${DESTDIR}${SERVICEDIR_DBUS}/org.knopwob.dunst.service
-	rm -f ${DESTDIR}${SERVICEDIR_SYSTEMD}/dunst.service
 	rm -rf ${DESTDIR}${PREFIX}/share/dunst
+
+uninstall-service: uninstall-service-dbus
+uninstall-service-dbus:
+	rm -f ${DESTDIR}${SERVICEDIR_DBUS}/org.knopwob.dunst.service
+
+ifneq (0,${SYSTEMD})
+uninstall-service: uninstall-service-systemd
+uninstall-service-systemd:
+	rm -f ${DESTDIR}${SERVICEDIR_SYSTEMD}/dunst.service
+endif

config.mk

@@ -2,6 +2,10 @@
 PREFIX ?= /usr/local
 MANPREFIX = ${PREFIX}/share/man
 
+# Disable systemd service file installation,
+# if you don't want to use systemd albeit installed
+#SYSTEMD ?= 0
+
 # uncomment to disable parsing of dunstrc
 # or use "CFLAGS=-DSTATIC_CONFIG make" to build
 #STATIC= -DSTATIC_CONFIG # Warning: This is deprecated behavior