x11-wm/fvwm3: Add .desktop entry for XSession

Add a .desktop file of type XSession, so fvwm3 is discoverable for
display managers following freedesktop.org standards.

PR:		272836
Co-authored-by:	Bartek Jasicki <thindil@laeran.pl.eu.org>

x11-wm/fvwm3/Makefile

@@ -1,6 +1,6 @@
 PORTNAME=	fvwm3
 DISTVERSION=	1.0.7
-PORTREVISION=	1
+PORTREVISION=	2
 CATEGORIES=	x11-wm
 MASTER_SITES=	https://github.com/fvwmorg/fvwm3/releases/download/${DISTVERSION}/ \
 		http://fvwm.sourceforge.net/generated/icon_download/:icons
@@ -25,6 +25,7 @@ GNU_CONFIGURE=	yes
 CONFIGURE_ARGS=	ac_cv_path_PYTHON=${PYTHON_CMD}
 
 CONFLICTS_INSTALL=	fvwm
+SUB_FILES=		fvwm3.desktop
 PLIST_SUB=		DISTVERSION=${DISTVERSION}
 
 OPTIONS_DEFINE=		FRIBIDI GO ICONS ICONV MANPAGES NLS PERL PNG SVG \
@@ -74,6 +75,11 @@ post-patch:
 	@${REINPLACE_CMD} -e 's,/etc/,${LOCALBASE}/etc/,g' \
 		${WRKSRC}/bin/fvwm-menu-desktop.in
 
+post-install:
+	${MKDIR} ${STAGEDIR}${PREFIX}/share/xsessions
+	${INSTALL_DATA} ${WRKDIR}/fvwm3.desktop \
+		${STAGEDIR}${PREFIX}/share/xsessions
+
 post-install-ICONS-on:
 	${MKDIR} ${STAGEDIR}${PREFIX}/share/fvwm3/pixmaps
 	${INSTALL_DATA} ${WRKDIR}/${FVWM_ICONS}/*.xpm \

x11-wm/fvwm3/files/fvwm3.desktop.in

@@ -0,0 +1,6 @@
+[Desktop Entry]
+Name=FVWM3
+Comment=The fvwm3 window manager
+Type=XSession
+Exec=%%PREFIX%%/bin/fvwm3
+TryExec=%%PREFIX%%/bin/fvwm3

x11-wm/fvwm3/pkg-plist

@@ -125,6 +125,7 @@ libexec/fvwm3/%%DISTVERSION%%/FvwmTalk
 %%DATADIR%%/default-config/stalonetrayrc
 %%DATADIR%%/fvwm-menu-desktop-config.fpl
 %%DATADIR%%/fvwm-script-ComExample.pl
+share/xsessions/fvwm3.desktop
 %%PERL%%%%DATADIR%%/perllib/FVWM/Commands.pm
 %%PERL%%%%DATADIR%%/perllib/FVWM/Constants.pm
 %%PERL%%%%DATADIR%%/perllib/FVWM/Event.pm