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

configure

@@ -46,6 +46,9 @@ param_set("vulkan-string-helper", 1);
 param_set("shared",               1);
 param_set("static",               1);
 param_set("examples",             1);
+if($target eq "Linux") {
+    param_set("x11",          1);
+}
 if($target eq "Linux") {
     param_set("wayland",          1);
 }

pl/ostype/Linux.pl

@@ -1,8 +1,12 @@
+my @enabled_backends=();
+
 if (param_get("wayland")) {
-    use_backend("wayland", "x11");
+    push(@enabled_backends,"wayland");
 }
-else {
-    use_backend("x11");
+if (param_get("x11")) {
+    push(@enabled_backends,"x11");
 }
 
+use_backend(@enabled_backends);
+
 1;

pl/rules.pl

@@ -8,13 +8,11 @@ if (param_get("classic-theme")) {
 if (grep(/^x11$/, @backends)) {
     add_cflags("-DUSE_X11");
     new_object("src/backend/x11.c");
-    #add_libs("-lX11");
 
     $gl_libs = "-lGL -lGLU";
 
     if (param_get("xrender")) {
         add_cflags("-DUSE_XRENDER");
-        #add_libs("-lXrender");
     }
 }
 

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;
 }