Made Xxf86vm optional at compile-time.

src/x11_platform.h

@@ -37,9 +37,6 @@
 #include <X11/Xatom.h>
 #include <X11/Xcursor/Xcursor.h>
 
-// The Xf86VidMode extension provides fallback gamma control
-#include <X11/extensions/xf86vmode.h>
-
 // The XRandR extension provides mode setting and gamma control
 #include <X11/extensions/Xrandr.h>
 
@@ -54,6 +51,11 @@
  #include <X11/extensions/XInput2.h>
 #endif
 
+#if defined(_GLFW_HAS_XF86VM)
+ // The Xf86VidMode extension provides fallback gamma control
+ #include <X11/extensions/xf86vmode.h>
+#endif
+
 #include "posix_tls.h"
 
 #if defined(_GLFW_GLX)
@@ -164,12 +166,6 @@ typedef struct _GLFWlibraryX11
     Atom            ATOM_PAIR;
     Atom            GLFW_SELECTION;
 
-    struct {
-        GLboolean   available;
-        int         eventBase;
-        int         errorBase;
-    } vidmode;
-
     struct {
         GLboolean   available;
         int         eventBase;
@@ -219,6 +215,14 @@ typedef struct _GLFWlibraryX11
     } xi;
 #endif /*_GLFW_HAS_XINPUT*/
 
+#if defined(_GLFW_HAS_XF86VM)
+    struct {
+        GLboolean   available;
+        int         eventBase;
+        int         errorBase;
+    } vidmode;
+#endif /*_GLFW_HAS_XF86VM*/
+
 } _GLFWlibraryX11;