diff --git a/src/fl_overlay_visual.cxx b/src/fl_overlay_visual.cxx
deleted file mode 100644
index aadd6fdb2..000000000
--- a/src/fl_overlay_visual.cxx
+++ /dev/null
@@ -1,90 +0,0 @@
-//
-// X overlay support for the Fast Light Tool Kit (FLTK).
-//
-// Copyright 1998-2018 by Bill Spitzak and others.
-//
-// This library is free software. Distribution and use rights are outlined in
-// the file "COPYING" which should have been included with this file.  If this
-// file is missing or damaged, see the license at:
-//
-//     https://www.fltk.org/COPYING.php
-//
-// Please see the following page on how to report bugs and issues:
-//
-//     https://www.fltk.org/bugs.php
-//
-
-// Return an overlay visual, if any.  Also allocate a colormap and
-// record the depth for fl_color() to use.
-// Another disgusting X interface, based on code extracted and
-// purified with great difficulty from XLayerUtil.cxx:
-
-#include <config.h>
-#if HAVE_OVERLAY
-#include <FL/Fl.H>
-#include <FL/platform.H>
-
-// SERVER_OVERLAY_VISUALS property element:
-struct OverlayInfo {
-  long overlay_visual;
-  long transparent_type;
-  long value;
-  long layer;
-};
-
-extern Colormap fl_overlay_colormap;
-extern XVisualInfo* fl_overlay_visual;
-extern ulong fl_transparent_pixel;
-
-XVisualInfo *fl_find_overlay_visual() {
-  static char beenhere;
-  if (beenhere) return fl_overlay_visual;
-  beenhere = 1;
-
-  fl_open_display();
-  Atom overlayVisualsAtom =
-    XInternAtom(fl_display,"SERVER_OVERLAY_VISUALS",1);
-  if (!overlayVisualsAtom) return 0;
-  OverlayInfo *overlayInfo;
-  ulong sizeData, bytesLeft;
-  Atom actualType;
-  int actualFormat;
-  if (XGetWindowProperty(fl_display, RootWindow(fl_display, fl_screen),
-                         overlayVisualsAtom, 0L, 10000L, False,
-                         overlayVisualsAtom, &actualType, &actualFormat,
-                         &sizeData, &bytesLeft,
-                         (unsigned char **) &overlayInfo)) return 0;
-
-  if (actualType == overlayVisualsAtom && actualFormat == 32) {
-    int n = int(sizeData/4);
-    XVisualInfo* v = 0;
-    // find the greatest depth that has a transparent pixel:
-    for (int i = 0; i < n; i++) {
-      if (overlayInfo[i].transparent_type != 1) continue;
-      if (overlayInfo[i].layer <= 0) continue;
-      XVisualInfo templt;
-      templt.visualid = overlayInfo[i].overlay_visual;
-      int num;
-      XVisualInfo *v1=XGetVisualInfo(fl_display, VisualIDMask, &templt, &num);
-      if (v1->screen == fl_screen && v1->c_class == PseudoColor
-          && (!v || v1->depth > v->depth && v1->depth <= 8)) {
-        if (v) XFree((char*)v);
-        v = v1;
-        fl_transparent_pixel = overlayInfo[i].value;
-      } else {
-        XFree((char*)v1);
-      }
-    }
-    if (v) {
-      fl_overlay_visual = v;
-      fl_overlay_colormap =
-        XCreateColormap(fl_display, RootWindow(fl_display, fl_screen),
-                        v->visual, AllocNone);
-    }
-  }
-  XFree((char*)overlayInfo);
-  //printf("overlay visual %ld selected\n", fl_overlay_visual->visualid);
-  return fl_overlay_visual;
-}
-
-#endif