//
// 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
