XRandR: make core dependency

RandR is sufficiently ubiquitous across Linux distributions and BSDs
that trying to maintain compatibility without it is not worth the
effort.

Although this might upset some people with very old SPARC machines or
ailing VAX machines, other even older WMs (FVWM1x/OLVWM) are available.

configure.ac

@@ -525,31 +525,16 @@ AH_TEMPLATE([HAVE_TAILQ],[Check if tailq is present.])
 AC_CHECK_HEADER(queue.h, AC_DEFINE(HAVE_TAILQ))
 
 # ********* XRandR
-problem_xrandr=""
-
-AC_ARG_ENABLE(xrandr,
-  AS_HELP_STRING([--disable-xrandr],[disable XRandR support]),
-  [ if test x"$enableval" = xyes; then
-    with_xrandr="yes, check"
-  else
-    with_xrandr="no"
-    problem_xrandr=": Explicitly disabled"
-  fi ],
-  [ with_xrandr="not specified, check" ]
-)
-
 AH_TEMPLATE([HAVE_XRANDR],[Define if XRandR library is used.])
-if test ! x"$with_xrandr" = xno; then
-    if $PKG_CONFIG --exists "xrandr >= 1.5.0"; then
-        AC_DEFINE(HAVE_XRANDR)
-        with_xrandr=yes
-        XRandR_LIBS=-lXrandr
-    else
-       with_xrandr=no
-       problem_xrandr="Couldn't detect libxrandr, or version < 1.5.0"
-    fi
-    #],[$X_LIBS $X_PRE_LIBS -lXext -lX11 $X_EXTRA_LIBS])
-fi
+AC_MSG_CHECKING([for XRandR...])
+PKG_CHECK_MODULES([xrandr], [xrandr >= 1.5],
+[
+	 AC_DEFINE(HAVE_XRANDR)
+         XRandR_LIBS=-lXrandr
+],
+[
+	 AC_MSG_ERROR([*** XRandR not found.  Install its header files. ***])
+])
 
 AC_SUBST(XRandR_LIBS)
 AC_SUBST(XRandR_CFLAGS)
@@ -1727,7 +1712,6 @@ Fvwm3 Configuration:
   With Session Management support?    $with_sm$problem_sm
   With SVG image support?             $with_rsvg$problem_rsvg
   With Xcursor support?               $with_xcursor$problem_xcursor
-  With XRandR support?                $with_xrandr$problem_xrandr
   With Xft anti-alias font support?   $with_xft$problem_xft
   With XPM image support?             $with_xpm$problem_xpm
   With Xrender image support?         $with_xrender$problem_xrender

libs/FScreen.c

@@ -323,7 +323,7 @@ scan_screens(Display *dpy)
 	rrm = XRRGetMonitors(dpy, root, false, &n);
 	if (n <= 0) {
 		fvwm_debug(__func__, "get monitors failed\n");
-		return;
+		exit(101);
 	}
 
 	for (i = 0; i < n; i++) {
@@ -390,9 +390,8 @@ void FScreenInit(Display *dpy)
 
 	if (!XRRQueryExtension(dpy, &randr_event, &err_base) ||
 	    !XRRQueryVersion (dpy, &major, &minor)) {
-		fvwm_debug(__func__,
-			   "RandR not present, falling back to single screen\n");
-		goto single_screen;
+		fvwm_debug(__func__, "RandR not present");
+		goto randr_fail;
 	}
 
 	if (major == 1 && minor >= 5)
@@ -403,9 +402,7 @@ void FScreenInit(Display *dpy)
 		/* Something went wrong. */
 		fvwm_debug(__func__, "Couldn't initialise XRandR: %s\n",
 			   strerror(errno));
-		fvwm_debug(__func__, "Falling back to single screen...\n");
-
-		goto single_screen;
+		goto randr_fail;
 	}
 
 	fvwm_debug(__func__, "Using RandR %d.%d\n", major, minor);
@@ -415,9 +412,8 @@ void FScreenInit(Display *dpy)
 
 	if (res == NULL || (res != NULL && res->noutput == 0)) {
 		XRRFreeScreenResources(res);
-		fvwm_debug(__func__, "RandR present, yet no ouputs found.  "
-			   "Using single screen...\n");
-		goto single_screen;
+		fvwm_debug(__func__, "RandR present, yet no ouputs found.");
+		goto randr_fail;
 	}
 	XRRFreeScreenResources(res);
 
@@ -435,17 +431,9 @@ void FScreenInit(Display *dpy)
 
 	return;
 
-single_screen:
-	m = monitor_new();
-	m->si->name = fxstrdup(GLOBAL_SCREEN_NAME);
-	m->si->rr_output = -1;
-	m->si->x = 0,
-	m->si->y = 0,
-	m->si->w = DisplayWidth(disp, DefaultScreen(disp)),
-	m->si->h = DisplayHeight(disp, DefaultScreen(disp));
-	m->flags |= MONITOR_NEW|MONITOR_PRIMARY;
-
-	TAILQ_INSERT_TAIL(&monitor_q, m, entry);
+randr_fail:
+	fprintf(stderr, "Unable to initialise RandR\n");
+	exit(101);
 }
 
 void