allow x11 backend to be disabled (on by default) (i doubt people will do this)

src/backend/x11.c

@@ -2301,10 +2301,16 @@ static void MwLLEndStateChangeImpl(MwLL handle) {
 
 static int MwLLX11CallInitImpl(void) {
 	xsymtbl.lib_xlib = MwDynamicOpen("libX11.so");
+	if(!xsymtbl.lib_xlib) {
+		return 1;
+	}
 
 #if USE_XRENDER
 	xsymtbl.lib_xrender = MwDynamicOpen("libXrender.so");
 #endif
+	if(!xsymtbl.lib_xrender) {
+		return 1;
+	}
 
 #define X11_FUNC_LOAD(x) x = MwDynamicSymbol(xsymtbl.lib_xlib, #x)
 

src/core.c

@@ -794,6 +794,21 @@ int MwLibraryInit(void) {
 		if(calls[i]() == 0) return 0;
 	}
 
+	printf("[WARNING] No suitable GUI backend found! Enabled:"
+#ifdef USE_COCOA
+	       " Cocoa"
+#endif
+#ifdef USE_WAYLAND
+	       " Wayland"
+#endif
+#ifdef USE_X11
+	       " X11"
+#endif
+#ifdef USE_GDI
+	       " GDI"
+#endif
+	       "\n");
+
 	return 1;
 }