build: make default backend configurable

Instead of hardcoding drm-backend.so as the default if environment
presents neither Wayland nor X11, have a ./configure option to change
it. It still defaults to drm-backend.so, if not given.

Signed-off-by: Pekka Paalanen <ppaalanen@gmail.com>

configure.ac

@@ -20,6 +20,9 @@ AC_PROG_SED
 LT_PREREQ([2.2])
 LT_INIT([disable-static])
 
+AC_ARG_VAR([WESTON_NATIVE_BACKEND],
+           [Set the native backend to use, if Weston is not running under Wayland nor X11. @<:@default=drm-backend.so@:>@])
+
 PKG_PROG_PKG_CONFIG()
 
 AC_CHECK_FUNC([dlopen], [],
@@ -255,6 +258,13 @@ fi
 AC_SUBST(GCC_CFLAGS)
 AC_SUBST(GCC_CXXFLAGS)
 
+if test "x$WESTON_NATIVE_BACKEND" = "x"; then
+	WESTON_NATIVE_BACKEND="drm-backend.so"
+fi
+AC_MSG_NOTICE([Weston's native backend: $WESTON_NATIVE_BACKEND])
+AC_DEFINE_UNQUOTED([WESTON_NATIVE_BACKEND], ["$WESTON_NATIVE_BACKEND"],
+		   [The default backend to load, if not wayland nor x11.])
+
 WAYLAND_SCANNER_RULES(['$(top_srcdir)/protocol'])
 
 AC_CONFIG_FILES([Makefile

man/Makefile.am

@@ -1,6 +1,7 @@
 man_MANS = weston.1
 
 MAN_SUBSTS = \
+	-e 's|__weston_native_backend__|$(WESTON_NATIVE_BACKEND)|g' \
 	-e 's|__weston_modules_dir__|$(pkglibdir)|g' \
 	-e 's|__version__|$(PACKAGE_VERSION)|g'
 

man/weston.man

@@ -98,7 +98,7 @@ Load
 instead of the default backend. The file is searched for in
 .IR "__weston_modules_dir__" ,
 or you can pass an absolute path. The default backend is 
-.I drm-backend.so
+.I __weston_native_backend__
 unless the environment suggests otherwise, see
 .IR DISPLAY " and " WAYLAND_DISPLAY .
 .TP

src/compositor.c

@@ -3151,7 +3151,7 @@ int main(int argc, char *argv[])
 		else if (getenv("DISPLAY"))
 			backend = "x11-backend.so";
 		else
-			backend = "drm-backend.so";
+			backend = WESTON_NATIVE_BACKEND;
 	}
 
 	config_file = config_file_path("weston.ini");