//
// Implementation of Wayland Screen interface
//
// Copyright 1998-2025 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
//

#include "Fl_Wayland_Screen_Driver.H"
#include "Fl_Wayland_Window_Driver.H"
#include "Fl_Wayland_Graphics_Driver.H"
#include "../../Fl_Scalable_Graphics_Driver.H"
#include <wayland-cursor.h>
#include "../../../libdecor/build/fl_libdecor.h"
#include "xdg-shell-client-protocol.h"
#include "../Posix/Fl_Posix_System_Driver.H"
#include <FL/Fl.H>
#include <FL/Fl_Image_Surface.H>
#include <FL/platform.H>
#include <FL/fl_ask.H>
#include <FL/filename.H>
#include <vector>
#include "../../print_button.h"
#include <dlfcn.h>
#include <linux/input.h>
#include <stdlib.h>
#include <xkbcommon/xkbcommon.h>
#include <xkbcommon/xkbcommon-compose.h>
#include "text-input-client-protocol.h"
#include "gtk-shell-client-protocol.h"
#include <assert.h>
#include <sys/mman.h>
#include <poll.h>
#include <errno.h>
#include <string.h> // for strerror()
extern "C" {
  bool libdecor_get_cursor_settings(char **theme, int *size);
  bool fl_is_surface_from_GTK_titlebar (struct wl_surface *surface, struct libdecor_frame *frame,
                                        bool *using_GTK);
}

// set this to 1 for keyboard debug output, 0 for no debug output
#define DEBUG_KEYBOARD 0

#define fl_max(a,b) ((a) > (b) ? (a) : (b))
#define fl_min(a,b) ((a) < (b) ? (a) : (b))

struct pointer_output {
  Fl_Wayland_Screen_Driver::output* output;
  struct wl_list link;
};

/* Implementation note:

- About CSD and SSD :
 * Mutter and Weston use CSD (client-side decoration) which means that libdecor.so draws all window
 titlebars and responds to resize, minimization and maximization events.
 * KWin uses SSD (server-side decoration) which means the OS draws titlebars according to its own rules
 and triggers resize, minimization and maximization events.

- Function registry_handle_global() runs within fl_open_display() and sets public static variable
 Fl_Wayland_Screen_Driver::compositor to either Fl_Wayland_Screen_Driver::MUTTER, ::WESTON, or ::KWIN.

- Specific operations for WESTON:
 * When a libdecor-framed window is minimized under Weston, the frame remains on display. To avoid
 that, function libdecor_frame_set_minimized() is modified so it turns off the frame's visibility, with
 function libdecor_frame_set_visibility(), when the window is minimized. That's implemented in file
 libdecor/build/fl_libdecor.c. The modified libdecor_frame_set_minimized() function, part of libdecor.so,
 needs access to variable Fl_Wayland_Screen_Driver::compositor, part of libfltk.a. This is achieved
 calling FLTK function fl_libdecor_using_weston() which returns whether the running compositor
 is Weston. This Weston bug has been corrected in Weston version 10. Thus, this special processing
 is not performed when Weston version is ≥ 10.

- Support of Fl_Window::border(int) :
 FLTK uses libdecor_frame_set_visibility() to show or hide a toplevel window's frame. This doesn't work
 with KWin which uses Server-Side Decoration. In that case, FLTK hides and re-shows the window to toggle
 between presence and absence of a window's frame.
*/


static std::vector<int> key_vector; // used by Fl_Wayland_Screen_Driver::event_key()
static struct wl_surface *gtk_shell_surface = NULL;

Fl_Wayland_Screen_Driver::compositor_name Fl_Wayland_Screen_Driver::compositor =
  Fl_Wayland_Screen_Driver::unspecified;


extern "C" {
  bool fl_libdecor_using_weston(void) {
    return Fl_Wayland_Screen_Driver::compositor == Fl_Wayland_Screen_Driver::WESTON;
  }
}


static void xdg_wm_base_ping(void *data, struct xdg_wm_base *xdg_wm_base, uint32_t serial)
{
    xdg_wm_base_pong(xdg_wm_base, serial);
}


static const struct xdg_wm_base_listener xdg_wm_base_listener = {
    .ping = xdg_wm_base_ping,
};


// these are set by Fl::args() and override any system colors: from Fl_get_system_colors.cxx
extern const char *fl_fg;
extern const char *fl_bg;
extern const char *fl_bg2;
// end of extern additions workaround


void Fl_Wayland_Screen_Driver::do_set_cursor(
    struct Fl_Wayland_Screen_Driver::seat *seat, struct wl_cursor *wl_cursor) {
  struct wl_cursor_image *image;
  struct wl_buffer *buffer;
  const int scale = seat->pointer_scale;

  if (!seat->cursor_theme || !seat->wl_pointer)
    return;

  if (!wl_cursor) wl_cursor = seat->default_cursor;
  image = wl_cursor->images[0];
  buffer = wl_cursor_image_get_buffer(image);
  wl_pointer_set_cursor(seat->wl_pointer, seat->pointer_enter_serial,
            seat->cursor_surface,
            image->hotspot_x / scale,
            image->hotspot_y / scale);
  wl_surface_attach(seat->cursor_surface, buffer, 0, 0);
  wl_surface_set_buffer_scale(seat->cursor_surface, scale);
  wl_surface_damage_buffer(seat->cursor_surface, 0, 0,
         image->width, image->height);
  wl_surface_commit(seat->cursor_surface);
}


static uint32_t ptime;
static uint32_t wld_event_time;
static int px, py;


static void set_event_xy(Fl_Window *win) {
  // turn off is_click if enough time or mouse movement has passed:
  if (abs(Fl::e_x_root-px)+abs(Fl::e_y_root-py) > 3 ||
      wld_event_time >= ptime+1000) {
    Fl::e_is_click = 0;
//fprintf(stderr, "Fl::e_is_click = 0\n");
  }
}


// if this is same event as last && is_click, increment click count:
static inline void checkdouble() {
  if (Fl::e_is_click == Fl::e_keysym) {
    Fl::e_clicks++;
//fprintf(stderr, "Fl::e_clicks = %d\n", Fl::e_clicks);
  } else {
    Fl::e_clicks = 0;
    Fl::e_is_click = Fl::e_keysym;
//fprintf(stderr, "Fl::e_is_click = %d\n", Fl::e_is_click);
  }
  px = Fl::e_x_root;
  py = Fl::e_y_root;
  ptime = wld_event_time;
}


struct wl_display *Fl_Wayland_Screen_Driver::wl_display = NULL;


static Fl_Window *event_coords_from_surface(struct wl_surface *surface,
                                       wl_fixed_t surface_x, wl_fixed_t surface_y) {
  Fl_Window *win = Fl_Wayland_Window_Driver::surface_to_window(surface);
  if (!win) return NULL;
  int delta_x = 0, delta_y = 0;
  while (win->parent()) {
    delta_x += win->x();
    delta_y += win->y();
    win = win->window();
  }
  float f = Fl::screen_scale(win->screen_num());
  Fl::e_x = wl_fixed_to_int(surface_x) / f + delta_x;
  Fl::e_x_root = Fl::e_x + win->x();
  Fl::e_y = wl_fixed_to_int(surface_y) / f + delta_y;
  int *poffset = Fl_Window_Driver::menu_offset_y(win);
  if (poffset) Fl::e_y -= *poffset;
  Fl::e_y_root = Fl::e_y + win->y();
  return win;
}


static void pointer_enter(void *data, struct wl_pointer *wl_pointer, uint32_t serial,
        struct wl_surface *surface, wl_fixed_t surface_x, wl_fixed_t surface_y) {
  struct Fl_Wayland_Screen_Driver::seat *seat = (struct Fl_Wayland_Screen_Driver::seat*)data;
  Fl_Window *win = event_coords_from_surface(surface, surface_x, surface_y);
  static bool using_GTK = seat->gtk_shell &&
    (gtk_shell1_get_version(seat->gtk_shell) >= GTK_SURFACE1_TITLEBAR_GESTURE_SINCE_VERSION);
  if (!win && using_GTK) {
    // check whether surface is the headerbar of a GTK-decorated window
    Fl_X *xp = Fl_X::first;
    while (xp && using_GTK) { // all mapped windows
      struct wld_window *xid = (struct wld_window*)xp->xid;
      if (xid->kind == Fl_Wayland_Window_Driver::DECORATED &&
          fl_is_surface_from_GTK_titlebar(surface, xid->frame, &using_GTK)) {
        gtk_shell_surface = surface;
        break;
      }
      xp = xp->next;
    }
  }
  if (!win) return;
  // use custom cursor if present
  struct wl_cursor *cursor =
    fl_wl_xid(win)->custom_cursor ? fl_wl_xid(win)->custom_cursor->wl_cursor : NULL;
  Fl_Wayland_Screen_Driver::do_set_cursor(seat, cursor);
  seat->serial = serial;
  seat->pointer_enter_serial = serial;
  set_event_xy(win);
  Fl::handle(FL_ENTER, win);
  //fprintf(stderr, "pointer_enter window=%p\n", win);
  seat->pointer_focus = surface;
}


static void pointer_leave(void *data, struct wl_pointer *wl_pointer,
        uint32_t serial, struct wl_surface *surface) {
  struct Fl_Wayland_Screen_Driver::seat *seat = (struct Fl_Wayland_Screen_Driver::seat*)data;
  if (seat->pointer_focus == surface) seat->pointer_focus = NULL;
  Fl_Window *win = Fl_Wayland_Window_Driver::surface_to_window(surface);
  gtk_shell_surface = NULL;
  if (win) {
    Fl::belowmouse(0);
    set_event_xy(win);
    Fl::handle(FL_LEAVE, win->top_window());
  }
//fprintf(stderr, "pointer_leave surface=%p window=%p\n", surface, win);
}


static void pointer_motion(void *data, struct wl_pointer *wl_pointer,
         uint32_t time, wl_fixed_t surface_x, wl_fixed_t surface_y) {
  struct Fl_Wayland_Screen_Driver::seat *seat =
    (struct Fl_Wayland_Screen_Driver::seat*)data;
  Fl_Window *win = event_coords_from_surface(seat->pointer_focus, surface_x, surface_y);
  if (!win) return;
  if (Fl::grab() && !Fl::grab()->menu_window() && Fl::grab() != win) {
    // If there's an active, non-menu grab() and the pointer is in a window other than
    // the grab(), make e_x_root too large to be in any window
    Fl::e_x_root = 1000000;
  }
  else if (Fl_Window_Driver::menu_parent(NULL) && // any kind of menu is active now, and
      !win->menu_window() && // we enter a non-menu window
      win != Fl_Window_Driver::menu_parent(NULL) // that's not the window below the menu
      ) {
    Fl::e_x_root = 1000000; // make it too large to be in any window
  }
//fprintf(stderr, "FL_MOVE on win=%p to x:%dx%d root:%dx%d\n", win, Fl::e_x, Fl::e_y, Fl::e_x_root, Fl::e_y_root);
  wld_event_time = time;
  set_event_xy(win);
  Fl::handle(FL_MOVE, win);
}


//#include <FL/names.h>
static void pointer_button(void *data,
         struct wl_pointer *wl_pointer,
         uint32_t serial,
         uint32_t time,
         uint32_t button,
         uint32_t state)
{
  struct Fl_Wayland_Screen_Driver::seat *seat =
    (struct Fl_Wayland_Screen_Driver::seat*)data;
  if (gtk_shell_surface && state == WL_POINTER_BUTTON_STATE_PRESSED &&
      button == BTN_MIDDLE) {
    struct gtk_surface1 *gtk_surface = gtk_shell1_get_gtk_surface(seat->gtk_shell,gtk_shell_surface);
    gtk_surface1_titlebar_gesture(gtk_surface, serial, seat->wl_seat,
                                  GTK_SURFACE1_GESTURE_MIDDLE_CLICK);
    gtk_surface1_release(gtk_surface); // very necessary
    return;
  }
  seat->serial = serial;
  int event = 0;
  Fl_Window *win = Fl_Wayland_Window_Driver::surface_to_window(seat->pointer_focus);
  if (!win) return;
  win = win->top_window();
  wld_event_time = time;
  int b = 0;
  // Fl::e_state &= ~FL_BUTTONS;    // DO NOT reset the mouse button state!
  if (state == WL_POINTER_BUTTON_STATE_PRESSED) {
    if (button == BTN_LEFT)         { Fl::e_state |= FL_BUTTON1; b = 1; }
    else if (button == BTN_RIGHT)   { Fl::e_state |= FL_BUTTON3; b = 3; }
    else if (button == BTN_MIDDLE)  { Fl::e_state |= FL_BUTTON2; b = 2; }
    else if (button == BTN_BACK)    { Fl::e_state |= FL_BUTTON4; b = 4; } // ?
    else if (button == BTN_SIDE)    { Fl::e_state |= FL_BUTTON4; b = 4; } // OK: Debian 12
    else if (button == BTN_FORWARD) { Fl::e_state |= FL_BUTTON5; b = 5; } // ?
    else if (button == BTN_EXTRA)   { Fl::e_state |= FL_BUTTON5; b = 5; } // OK: Debian 12
  } else { // must be WL_POINTER_BUTTON_STATE_RELEASED
    if (button == BTN_LEFT)         { Fl::e_state &= ~FL_BUTTON1; b = 1; }
    else if (button == BTN_RIGHT)   { Fl::e_state &= ~FL_BUTTON3; b = 3; }
    else if (button == BTN_MIDDLE)  { Fl::e_state &= ~FL_BUTTON2; b = 2; }
    else if (button == BTN_BACK)    { Fl::e_state &= ~FL_BUTTON4; b = 4; } // ?
    else if (button == BTN_SIDE)    { Fl::e_state &= ~FL_BUTTON4; b = 4; } // OK: Debian 12
    else if (button == BTN_FORWARD) { Fl::e_state &= ~FL_BUTTON5; b = 5; } // ?
    else if (button == BTN_EXTRA)   { Fl::e_state &= ~FL_BUTTON5; b = 5; } // OK: Debian 12
  }
  Fl::e_keysym = FL_Button + b;
  Fl::e_dx = Fl::e_dy = 0;

  set_event_xy(win);
  if (state == WL_POINTER_BUTTON_STATE_PRESSED) {
    event = FL_PUSH;
    checkdouble();
  } else if (state == WL_POINTER_BUTTON_STATE_RELEASED) {
    event = FL_RELEASE;
  }
  // fprintf(stderr, "%s %s\n", fl_eventnames[event], win->label() ? win->label():"[]");
  Fl::handle(event, win);
}


static void pointer_axis(void *data, struct wl_pointer *wl_pointer,
       uint32_t time, uint32_t axis, wl_fixed_t value) {
  struct Fl_Wayland_Screen_Driver::seat *seat = (struct Fl_Wayland_Screen_Driver::seat*)data;
  Fl_Window *win = Fl_Wayland_Window_Driver::surface_to_window(seat->pointer_focus);
  if (!win) return;
  wld_event_time = time;
  int delta = wl_fixed_to_int(value);
  if (abs(delta) >= 10) delta /= 10;
  // fprintf(stderr, "FL_MOUSEWHEEL: %c delta=%d\n", axis==WL_POINTER_AXIS_HORIZONTAL_SCROLL?'H':'V', delta);
  // allow both horizontal and vertical movements to be processed by the widget
  if (axis == WL_POINTER_AXIS_HORIZONTAL_SCROLL) {
    if (Fl::event_shift()) { // shift key pressed: send vertical mousewheel event
      Fl::e_dx = 0;
      Fl::e_dy = delta;
    } else { // shift key not pressed (normal behavior): send horizontal mousewheel event
      Fl::e_dx = delta;
      Fl::e_dy = 0;
    }
    Fl::handle(FL_MOUSEWHEEL, win->top_window());
  }
  if (axis == WL_POINTER_AXIS_VERTICAL_SCROLL) {
    if (Fl::event_shift()) { // shift key pressed: send horizontal mousewheel event
      Fl::e_dx = delta;
      Fl::e_dy = 0;
    } else {// shift key not pressed (normal behavior): send vertical mousewheel event
      Fl::e_dx = 0;
      Fl::e_dy = delta;
    }
    Fl::handle(FL_MOUSEWHEEL, win->top_window());
  }
}


static struct wl_pointer_listener pointer_listener = {
  pointer_enter,
  pointer_leave,
  pointer_motion,
  pointer_button,
  pointer_axis
};


static const char *proxy_tag = "FLTK for Wayland";


bool Fl_Wayland_Screen_Driver::own_output(struct wl_output *output)
{
  return wl_proxy_get_tag((struct wl_proxy *)output) == &proxy_tag;
}


static void init_cursors(struct Fl_Wayland_Screen_Driver::seat *seat);


static void try_update_cursor(struct Fl_Wayland_Screen_Driver::seat *seat) {
  if (wl_list_empty(&seat->pointer_outputs)) return;
  struct pointer_output *pointer_output;
  int scale = 1;

  wl_list_for_each(pointer_output, &seat->pointer_outputs, link) {
    scale = fl_max(scale, pointer_output->output->wld_scale);
  }

  if (scale != seat->pointer_scale) {
    seat->pointer_scale = scale;
    init_cursors(seat);
    Fl_Wayland_Screen_Driver::do_set_cursor(seat);
  }
}


static void output_scale(void *data, struct wl_output *wl_output, int32_t factor);


static void cursor_surface_enter(void *data,
        struct wl_surface *wl_surface, struct wl_output *wl_output) {
  // Runs when the seat's cursor_surface enters a display
  struct Fl_Wayland_Screen_Driver::seat *seat =
    (struct Fl_Wayland_Screen_Driver::seat*)data;
  struct pointer_output *pointer_output;

  if (!Fl_Wayland_Screen_Driver::own_output(wl_output))
    return;

  pointer_output = (struct pointer_output *)calloc(1, sizeof(struct pointer_output));
  pointer_output->output =
    (Fl_Wayland_Screen_Driver::output *)wl_output_get_user_data(wl_output);
//fprintf(stderr, "cursor_surface_enter: wl_output_get_user_data(%p)=%p\n", wl_output, pointer_output->output);
  wl_list_insert(&seat->pointer_outputs, &pointer_output->link);
  try_update_cursor(seat);
  Fl_Wayland_Screen_Driver::output *output =
    (Fl_Wayland_Screen_Driver::output*)wl_output_get_user_data(wl_output);
  output_scale(output, wl_output, output->wld_scale); // rescale custom cursors
  // maintain custom or standard window cursor
  Fl_Window *win = Fl::first_window();
  if (win) {
    Fl_Wayland_Window_Driver *driver = Fl_Wayland_Window_Driver::driver(win);
    struct wld_window *xid = fl_wl_xid(win);
    if (xid->custom_cursor) Fl_Wayland_Screen_Driver::do_set_cursor(seat, xid->custom_cursor->wl_cursor);
    else if (driver->cursor_default()) driver->set_cursor(driver->cursor_default());
    else win->cursor(driver->standard_cursor());
  }
}


static void cursor_surface_leave(void *data, struct wl_surface *wl_surface,
        struct wl_output *wl_output) {
  struct Fl_Wayland_Screen_Driver::seat *seat =
    (struct Fl_Wayland_Screen_Driver::seat*)data;
  struct pointer_output *pointer_output, *tmp;
  wl_list_for_each_safe(pointer_output, tmp, &seat->pointer_outputs, link) {
    if (pointer_output->output->wl_output == wl_output) {
      wl_list_remove(&pointer_output->link);
      free(pointer_output);
    }
  }
  try_update_cursor(seat);
  // maintain custom window cursor
  Fl_Window *win = Fl::first_window();
  if (win) {
    struct wld_window *xid = fl_wl_xid(win);
    if (xid->custom_cursor) Fl_Wayland_Screen_Driver::do_set_cursor(seat, xid->custom_cursor->wl_cursor);
  }
}


static struct wl_surface_listener cursor_surface_listener = {
  cursor_surface_enter,
  cursor_surface_leave,
};


static void init_cursors(struct Fl_Wayland_Screen_Driver::seat *seat) {
  char *name;
  int size;
  struct wl_cursor_theme *theme;

  if (!libdecor_get_cursor_settings(&name, &size)) {
    name = NULL;
    size = 24;
  }
  size *= seat->pointer_scale;
  Fl_Wayland_Screen_Driver *scr_driver = (Fl_Wayland_Screen_Driver*)Fl::screen_driver();
  theme = wl_cursor_theme_load(name, size, scr_driver->wl_shm);
  free(name);
  //struct wl_cursor_theme *old_theme = seat->cursor_theme;
  if (theme != NULL) {
    if (seat->cursor_theme) {
     // caution to destroy theme because Fl_Wayland_Window_Driver::set_cursor(Fl_Cursor) caches used cursors
      scr_driver->reset_cursor();
      wl_cursor_theme_destroy(seat->cursor_theme);
    }
    seat->cursor_theme = theme;
  }
  if (seat->cursor_theme) {
    seat->default_cursor = scr_driver->xc_cursor[Fl_Wayland_Screen_Driver::arrow] =
      wl_cursor_theme_get_cursor(seat->cursor_theme, "left_ptr");
  }
  if (!seat->cursor_surface) {
    seat->cursor_surface = wl_compositor_create_surface(scr_driver->wl_compositor);
    wl_surface_add_listener(seat->cursor_surface, &cursor_surface_listener, seat);
  }
}


static void wl_keyboard_keymap(void *data, struct wl_keyboard *wl_keyboard,
               uint32_t format, int32_t fd, uint32_t size) {
  struct Fl_Wayland_Screen_Driver::seat *seat =
    (struct Fl_Wayland_Screen_Driver::seat*)data;
  assert(format == WL_KEYBOARD_KEYMAP_FORMAT_XKB_V1);

  char *map_shm = (char*)mmap(NULL, size, PROT_READ,
      wl_keyboard_get_version(wl_keyboard) >= 7 ? MAP_PRIVATE : MAP_SHARED, fd, 0);
  assert(map_shm != MAP_FAILED);

  struct xkb_keymap *xkb_keymap = xkb_keymap_new_from_string(seat->xkb_context, map_shm,
              XKB_KEYMAP_FORMAT_TEXT_V1, XKB_KEYMAP_COMPILE_NO_FLAGS);
  munmap(map_shm, size);
  close(fd);
  if (xkb_keymap) {
    struct xkb_state *xkb_state = xkb_state_new(xkb_keymap);
    xkb_keymap_unref(seat->xkb_keymap);
    if (seat->xkb_state) xkb_state_unref(seat->xkb_state);
    seat->xkb_keymap = xkb_keymap;
    seat->xkb_state = xkb_state;
  }
}


static int search_int_vector(std::vector<int>& v, int val) {
  for (unsigned pos = 0; pos < v.size(); pos++) {
    if (v[pos] == val) return pos;
  }
  return -1;
}


static void remove_int_vector(std::vector<int>& v, int val) {
  int pos = search_int_vector(v, val);
  if (pos < 0) return;
  v.erase(v.begin()+pos);
}


static int process_wld_key(struct xkb_state *xkb_state, uint32_t key,
                           uint32_t *p_keycode, xkb_keysym_t *p_sym) {
  uint32_t keycode = key + 8;
  xkb_keysym_t sym = xkb_state_key_get_one_sym(xkb_state, keycode);
  if (sym == 0xfe20) sym = FL_Tab;
  if (sym >= 'A' && sym <= 'Z') sym += 32; // replace uppercase by lowercase letter
  int for_key_vector = sym; // for support of Fl::event_key(int)
  // special processing for number keys == keycodes 10-19 :
  if (keycode >= 10 && keycode <= 18) {
    for_key_vector = '1' + (keycode - 10);
  } else if (keycode == 19) {
    for_key_vector = '0';
  }
  if (p_keycode) *p_keycode = keycode;
  if (p_sym) *p_sym = sym;
  return for_key_vector;
}


static uint32_t last_keydown_serial = 0; // serial of last keydown event


static void wl_keyboard_enter(void *data, struct wl_keyboard *wl_keyboard,
               uint32_t serial, struct wl_surface *surface, struct wl_array *keys) {
  struct Fl_Wayland_Screen_Driver::seat *seat =
    (struct Fl_Wayland_Screen_Driver::seat*)data;
//fprintf(stderr, "keyboard enter fl_win=%p; keys pressed are: ", Fl_Wayland_Window_Driver::surface_to_window(surface));
  key_vector.clear();
  // Replace wl_array_for_each(p, keys) rejected by C++
  for (uint32_t *p = (uint32_t *)(keys)->data;
      (const char *) p < ((const char *) (keys)->data + (keys)->size);
      (p)++) {
    int for_key_vector = process_wld_key(seat->xkb_state, *p, NULL, NULL);
//fprintf(stderr, "%d ", for_key_vector);
    if (search_int_vector(key_vector, for_key_vector) < 0) {
      key_vector.push_back(for_key_vector);
    }
  }
//fprintf(stderr, "\n");
  seat->keyboard_surface = surface;
  seat->keyboard_enter_serial = serial;
  last_keydown_serial = 0;
  Fl_Window *win = Fl_Wayland_Window_Driver::surface_to_window(surface);
  if (win) {
    Fl::handle(FL_FOCUS, win);
    fl_wl_find(fl_wl_xid(win));
  }
}


struct key_repeat_data_t {
  uint32_t serial;
  Fl_Window *window;
};

#define KEY_REPEAT_DELAY 0.5 // sec
#define KEY_REPEAT_INTERVAL 0.05 // sec


static void key_repeat_timer_cb(key_repeat_data_t *key_repeat_data) {
  if (last_keydown_serial == key_repeat_data->serial) {
    Fl::handle(FL_KEYDOWN, key_repeat_data->window);
    Fl::add_timeout(KEY_REPEAT_INTERVAL, (Fl_Timeout_Handler)key_repeat_timer_cb, key_repeat_data);
  }
  else delete key_repeat_data;
}


int Fl_Wayland_Screen_Driver::next_marked_length = 0;


int Fl_Wayland_Screen_Driver::has_marked_text() const {
  return 1;
}


int Fl_Wayland_Screen_Driver::insertion_point_x = 0;
int Fl_Wayland_Screen_Driver::insertion_point_y = 0;
int Fl_Wayland_Screen_Driver::insertion_point_width = 0;
int Fl_Wayland_Screen_Driver::insertion_point_height = 0;
bool Fl_Wayland_Screen_Driver::insertion_point_location_is_valid = false;

static int previous_cursor_x = 0, previous_cursor_y = 0, previous_cursor_h = 0;
static uint32_t commit_serial = 0;
static char *current_pre_edit = NULL;
static char *pending_pre_edit = NULL;
static char *pending_commit = NULL;


static void send_commit(struct zwp_text_input_v3 *zwp_text_input_v3) {
  zwp_text_input_v3_commit(zwp_text_input_v3);
  commit_serial++;
}


// inform TIM about location of the insertion point, and memorize this info.
void Fl_Wayland_Screen_Driver::insertion_point_location(int x, int y, int height) {
//printf("insertion_point_location %dx%d\n",x,y);
  Fl_Wayland_Screen_Driver *scr_driver = (Fl_Wayland_Screen_Driver*)Fl::screen_driver();
  if (scr_driver->seat->text_input /*&& !current_pre_edit*/ &&
        (x != previous_cursor_x || y != previous_cursor_y  || height != previous_cursor_h)) {
    previous_cursor_x = x;
    previous_cursor_y = y;
    previous_cursor_h = height;
    if (Fl::focus()) {
      Fl_Widget *focuswin = Fl::focus()->window();
      while (focuswin && focuswin->parent()) {
        x += focuswin->x(); y += focuswin->y();
        focuswin = focuswin->window();
      }
    }
    float s = fl_graphics_driver->scale();
    insertion_point_location_is_valid = true;
    insertion_point_x = s*x;
    insertion_point_y = s*(y-height);
    insertion_point_width = s*5;
    insertion_point_height = s*height;
    if (zwp_text_input_v3_get_user_data(scr_driver->seat->text_input) ) {
      zwp_text_input_v3_set_cursor_rectangle(scr_driver->seat->text_input,
                                             insertion_point_x, insertion_point_y,
                                             insertion_point_width, insertion_point_height);
      send_commit(scr_driver->seat->text_input);
    }
  }
}


// computes window coordinates & size of insertion point
bool Fl_Wayland_Screen_Driver::insertion_point_location(int *px, int *py,
                                                        int *pwidth, int *pheight) {
  // return true if the current coordinates and size of the insertion point are available
  if ( ! insertion_point_location_is_valid ) return false;
  *px = insertion_point_x;
  *py = insertion_point_y;
  *pwidth = insertion_point_width;
  *pheight = insertion_point_height;
  return true;
}


int Fl_Wayland_Screen_Driver::compose(int& del) {
  unsigned char ascii = (unsigned char)Fl::e_text[0];
  // letter+modifier key
  int condition = (Fl::e_state & (FL_ALT | FL_META | FL_CTRL)) && ascii < 128 ;
  // pressing modifier key
  // FL_Shift_L, FL_Shift_R, FL_Control_L, FL_Control_R, FL_Caps_Lock
  // FL_Meta_L, FL_Meta_R, FL_Alt_L, FL_Alt_R
  condition |= ((Fl::e_keysym >= FL_Shift_L && Fl::e_keysym <= FL_Alt_R) ||
                Fl::e_keysym == FL_Alt_Gr);
  // FL_Home FL_Left FL_Up FL_Right FL_Down FL_Page_Up FL_Page_Down FL_End
  // FL_Print FL_Insert FL_Menu FL_Help and more
  condition |= (Fl::e_keysym >= FL_Home && Fl::e_keysym <= FL_Help);
  condition |= Fl::e_keysym == FL_Tab;
//fprintf(stderr, "compose: condition=%d e_state=%x ascii=%d\n", condition, Fl::e_state, ascii);
  if (condition) { del = 0; return 0;}
//fprintf(stderr, "compose: del=%d compose_state=%d next_marked_length=%d \n", del, Fl::compose_state, next_marked_length);
  del = Fl::compose_state;
  Fl::compose_state = next_marked_length;
  // no-underlined-text && (ascii non-printable || ascii == delete)
  if (ascii && (!Fl::compose_state) && (ascii <= 31 || ascii == 127)) { del = 0; return 0; }
  return 1;
}


void Fl_Wayland_Screen_Driver::compose_reset() {
  if (!Fl_Wayland_Screen_Driver::wl_registry) open_display();
  Fl::compose_state = 0;
  next_marked_length = 0;
  if (seat->xkb_compose_state) xkb_compose_state_reset(seat->xkb_compose_state);
}


struct dead_key_struct {
  xkb_keysym_t keysym; // the keysym obtained when hitting a dead key
  const char *marked_text; // the temporary text to display for that dead key
};


static dead_key_struct dead_keys[] = {
  {XKB_KEY_dead_grave, "`"},
  {XKB_KEY_dead_acute, "´"},
  {XKB_KEY_dead_circumflex, "^"},
  {XKB_KEY_dead_tilde, "~"},
  {XKB_KEY_dead_macron, "¯"},
  {XKB_KEY_dead_breve, "˘"},
  {XKB_KEY_dead_abovedot, "˙"},
  {XKB_KEY_dead_diaeresis, "¨"},
  {XKB_KEY_dead_abovering, "˚"},
  {XKB_KEY_dead_doubleacute, "˝"},
  {XKB_KEY_dead_caron, "ˇ"},
  {XKB_KEY_dead_cedilla, "¸"},
  {XKB_KEY_dead_ogonek, "˛"},
  {XKB_KEY_dead_iota, "ι"},
  {XKB_KEY_dead_doublegrave, " ̏"},
};


const int dead_key_count = sizeof(dead_keys)/sizeof(struct dead_key_struct);

static void wl_keyboard_key(void *data, struct wl_keyboard *wl_keyboard,
               uint32_t serial, uint32_t time, uint32_t key, uint32_t state) {
  struct Fl_Wayland_Screen_Driver::seat *seat =
    (struct Fl_Wayland_Screen_Driver::seat*)data;
  seat->serial = serial;
  static char buf[128];
  uint32_t keycode;
  xkb_keysym_t sym;
  int for_key_vector = process_wld_key(seat->xkb_state, key, &keycode, &sym);
#if (DEBUG_KEYBOARD)
  xkb_keysym_get_name(sym, buf, sizeof(buf));
  const char *action = (state == WL_KEYBOARD_KEY_STATE_PRESSED ? "press" : "release");
  fprintf(stderr, "wl_keyboard_key: key %s: sym: %-12s(%d) code:%u fl_win=%p, ",
          action, buf, sym, keycode,
          Fl_Wayland_Window_Driver::surface_to_window(seat->keyboard_surface));
#endif
  xkb_state_key_get_utf8(seat->xkb_state, keycode, buf, sizeof(buf));
#if (DEBUG_KEYBOARD)
  fprintf(stderr, "utf8: '%s' e_length=%d [%d]\n", buf, (int)strlen(buf), *buf);
#endif
  Fl::e_keysym = Fl::e_original_keysym = for_key_vector;
  if (!(Fl::e_state & FL_NUM_LOCK) && sym >= XKB_KEY_KP_Home && sym <= XKB_KEY_KP_Delete) {
    // compute e_keysym and e_original_keysym for keypad number keys and '.|,' when NumLock is off
    static const int table[11] = {FL_Home      /* 7 */, FL_Left   /* 4 */, FL_Up      /* 8 */,
                                  FL_Right     /* 6 */, FL_Down   /* 2 */, FL_Page_Up /* 9 */,
                                  FL_Page_Down /* 3 */, FL_End    /* 1 */, 0xff0b     /* 5 */,
                                  FL_Insert    /* 0 */, FL_Delete /* .|, */};
    static const int table_original[11] = {0xffb7 /* 7 */, 0xffb4 /* 4 */, 0xffb8 /* 8 */,
                                           0xffb6 /* 6 */, 0xffb2 /* 2 */, 0xffb9 /* 9 */,
                                           0xffb3 /* 3 */, 0xffb1 /* 1 */, 0xffb5 /* 5 */,
                                           0xffb0 /* 0 */, 0xffac /* .|, */};
    Fl::e_keysym          =          table[sym - XKB_KEY_KP_Home];
    Fl::e_original_keysym = table_original[sym - XKB_KEY_KP_Home];
    for_key_vector = Fl::e_original_keysym;
  }
#if (DEBUG_KEYBOARD)
  fprintf(stderr, "wl_keyboard_key: e_keysym=%x e_original_keysym=%x\n", Fl::e_keysym, Fl::e_original_keysym);
#endif
  if (state == WL_KEYBOARD_KEY_STATE_PRESSED) {
    if (search_int_vector(key_vector, for_key_vector) < 0) {
      key_vector.push_back(for_key_vector);
    }
  } else {
    last_keydown_serial = 0;
    remove_int_vector(key_vector, for_key_vector);
  }
  Fl::e_text = buf;
  Fl::e_length = (int)strlen(buf);
  // Process dead keys and compose sequences :
  enum xkb_compose_status status = XKB_COMPOSE_NOTHING;
  // This part is useful only if the compositor doesn't support protocol text-input-unstable-v3
  if (seat->xkb_compose_state && state == WL_KEYBOARD_KEY_STATE_PRESSED &&
      !(sym >= FL_Shift_L && sym <= FL_Alt_R) && sym != XKB_KEY_ISO_Level3_Shift) {
    xkb_compose_state_feed(seat->xkb_compose_state, sym);
    status = xkb_compose_state_get_status(seat->xkb_compose_state);
    if (status == XKB_COMPOSE_COMPOSING) {
      if (Fl::e_length == 0) { // dead keys produce e_length = 0
        int i;
        for (i = 0; i < dead_key_count; i++) {
          if (dead_keys[i].keysym == sym) break;
        }
        if (i < dead_key_count) strcpy(buf, dead_keys[i].marked_text);
        else buf[0] = 0;
        Fl::e_length = (int)strlen(buf);
        Fl::compose_state = 0;
      }
      Fl_Wayland_Screen_Driver::next_marked_length = Fl::e_length;
    } else if (status == XKB_COMPOSE_COMPOSED) {
      Fl::e_length = xkb_compose_state_get_utf8(seat->xkb_compose_state, buf, sizeof(buf));
      Fl::compose_state = Fl_Wayland_Screen_Driver::next_marked_length;
      Fl_Wayland_Screen_Driver::next_marked_length = 0;
    } else if (status == XKB_COMPOSE_CANCELLED) {
      Fl::e_length = 0;
      Fl::compose_state = Fl_Wayland_Screen_Driver::next_marked_length;
      Fl_Wayland_Screen_Driver::next_marked_length = 0;
    }
//fprintf(stderr, "xkb_compose_status=%d ctxt=%p state=%p l=%d[%s]\n", status, seat->xkb_context, seat->xkb_compose_state, Fl::e_length, buf);
  }
  // end of part used only without text-input-unstable-v3

  wld_event_time = time;
  int event = (state == WL_KEYBOARD_KEY_STATE_PRESSED ? FL_KEYDOWN : FL_KEYUP);
  // Send event to focus-containing top window as defined by FLTK,
  // otherwise send it to Wayland-defined focus window
  Fl_Window *win = ( Fl::focus() ? Fl::focus()->top_window() :
                    Fl_Wayland_Window_Driver::surface_to_window(seat->keyboard_surface) );
  if (win) {
    set_event_xy(win);
    Fl::e_is_click = 0;
    Fl::handle(event, win);
  }
  if (event == FL_KEYDOWN && status == XKB_COMPOSE_NOTHING &&
      !(sym >= FL_Shift_L && sym <= FL_Alt_R)) {
    // Handling of key repeats :
    // Use serial argument rather than time to detect repeated keys because
    // serial value changes at each key up or down in all tested OS and compositors,
    // whereas time value changes in Ubuntu24.04 KDE/Plasma 5.27.11 and Ubuntu22.04 KDE/Plasma 5.24.7
    // but not in Debian-testing KDE/Plasma 5.27.10.
    // Unexplained difference in behaviors of KDE/Plasma compositor:
    // Consider KDE settings -> input -> keyboard -> when a key is held: repeat/do nothing.
    // This setting (repeat) has key-down wayland events repeated when key is held under Debian/KDE
    // but not under Ubuntu/KDE !
    key_repeat_data_t *key_repeat_data = new key_repeat_data_t;
    key_repeat_data->serial = serial;
    key_repeat_data->window = win;
    last_keydown_serial = serial;
    Fl::add_timeout(KEY_REPEAT_DELAY, (Fl_Timeout_Handler)key_repeat_timer_cb,
                    key_repeat_data);
  }
}


static void wl_keyboard_leave(void *data, struct wl_keyboard *wl_keyboard,
               uint32_t serial, struct wl_surface *surface) {
  struct Fl_Wayland_Screen_Driver::seat *seat = (struct Fl_Wayland_Screen_Driver::seat*)data;
//fprintf(stderr, "keyboard leave fl_win=%p\n", Fl_Wayland_Window_Driver::surface_to_window(surface));
  seat->keyboard_surface = NULL;
  last_keydown_serial = 0;
  Fl_Window *win = Fl_Wayland_Window_Driver::surface_to_window(surface);
  if (!win && Fl::focus()) win = Fl::focus()->top_window();
  if (win) Fl::handle(FL_UNFOCUS, win);
  key_vector.clear();
}


static void wl_keyboard_modifiers(void *data, struct wl_keyboard *wl_keyboard,
               uint32_t serial, uint32_t mods_depressed,
               uint32_t mods_latched, uint32_t mods_locked,
               uint32_t group) {
  struct Fl_Wayland_Screen_Driver::seat *seat =
    (struct Fl_Wayland_Screen_Driver::seat*)data;
  xkb_state_update_mask(seat->xkb_state, mods_depressed, mods_latched, mods_locked,
                        0, 0, group);
  Fl::e_state &= ~(FL_SHIFT+FL_CTRL+FL_ALT+FL_CAPS_LOCK+FL_NUM_LOCK);
  if (xkb_state_mod_name_is_active(seat->xkb_state, XKB_MOD_NAME_SHIFT,
                                   XKB_STATE_MODS_DEPRESSED)) Fl::e_state |= FL_SHIFT;
  if (xkb_state_mod_name_is_active(seat->xkb_state, XKB_MOD_NAME_CTRL,
                                   XKB_STATE_MODS_DEPRESSED)) Fl::e_state |= FL_CTRL;
  if (xkb_state_mod_name_is_active(seat->xkb_state, XKB_MOD_NAME_ALT,
                                   XKB_STATE_MODS_DEPRESSED)) Fl::e_state |= FL_ALT;
  if (xkb_state_mod_name_is_active(seat->xkb_state, XKB_MOD_NAME_CAPS,
                                   XKB_STATE_MODS_LOCKED)) Fl::e_state |= FL_CAPS_LOCK;
  if (xkb_state_mod_name_is_active(seat->xkb_state, XKB_MOD_NAME_NUM,
                                   XKB_STATE_MODS_LOCKED)) Fl::e_state |= FL_NUM_LOCK;
//fprintf(stderr, "mods_depressed=%u Fl::e_state=%X\n", mods_depressed, Fl::e_state);
}


static void wl_keyboard_repeat_info(void *data, struct wl_keyboard *wl_keyboard, int32_t rate, int32_t delay)
{
  // wl_keyboard is version 3 under Debian, but that event isn't sent until version 4
}


static const struct wl_keyboard_listener wl_keyboard_listener = {
       .keymap = wl_keyboard_keymap,
       .enter = wl_keyboard_enter,
       .leave = wl_keyboard_leave,
       .key = wl_keyboard_key,
       .modifiers = wl_keyboard_modifiers,
       .repeat_info = wl_keyboard_repeat_info,
};


void text_input_enter(void *data, struct zwp_text_input_v3 *zwp_text_input_v3,
                      struct wl_surface *surface) {
//puts("text_input_enter");
  zwp_text_input_v3_set_user_data(zwp_text_input_v3, surface);
  zwp_text_input_v3_enable(zwp_text_input_v3);
  zwp_text_input_v3_set_content_type(zwp_text_input_v3, ZWP_TEXT_INPUT_V3_CONTENT_HINT_NONE, ZWP_TEXT_INPUT_V3_CONTENT_PURPOSE_NORMAL);
  int x, y, width, height;
  if (Fl_Wayland_Screen_Driver::insertion_point_location(&x, &y, &width, &height)) {
    zwp_text_input_v3_set_cursor_rectangle(zwp_text_input_v3,  x,  y,  width, height);
  }
  send_commit(zwp_text_input_v3);
}


void text_input_leave(void *data, struct zwp_text_input_v3 *zwp_text_input_v3,
                      struct wl_surface *surface) {
//puts("text_input_leave");
  zwp_text_input_v3_disable(zwp_text_input_v3);
  zwp_text_input_v3_set_user_data(zwp_text_input_v3, NULL);
  send_commit(zwp_text_input_v3);
  free(pending_pre_edit); pending_pre_edit = NULL;
  free(current_pre_edit); current_pre_edit = NULL;
  free(pending_commit); pending_commit = NULL;
}


static void send_text_to_fltk(const char *text, bool is_marked, struct wl_surface *current_surface) {
//printf("send_text_to_fltk(%s, %d)\n",text,is_marked);
  Fl_Window *win =  Fl_Wayland_Window_Driver::surface_to_window(current_surface);
  Fl::e_text = text ? (char*)text : (char*)"";
  Fl::e_length = text ? (int)strlen(text) : 0;
  Fl::e_keysym = 'a'; // fake a simple key
  set_event_xy(win);
  Fl::e_is_click = 0;
  if (is_marked) { // goes to widget as marked text
    Fl_Wayland_Screen_Driver::next_marked_length = Fl::e_length;
    Fl::handle(FL_KEYDOWN, win);
  } else if (text) {
    Fl_Wayland_Screen_Driver::next_marked_length = 0;
    Fl::handle(FL_KEYDOWN, win);
    Fl::compose_state = 0;
  } else {
    Fl_Wayland_Screen_Driver::next_marked_length = 0;
    Fl::handle(FL_KEYDOWN, win);
  }
}


void text_input_preedit_string(void *data, struct zwp_text_input_v3 *zwp_text_input_v3,
           const char *text, int32_t cursor_begin, int32_t cursor_end) {
//printf("text_input_preedit_string %s cursor_begin=%d cursor_end=%d\n",text, cursor_begin, cursor_end);
  free(pending_pre_edit);
  pending_pre_edit = text ? strdup(text) : NULL;
}


void text_input_commit_string(void *data, struct zwp_text_input_v3 *zwp_text_input_v3,
                              const char *text) {
//printf("text_input_commit_string %s\n",text);
  free(pending_commit);
  pending_commit = text ? strdup(text) : NULL;
}


void text_input_delete_surrounding_text(void *data,
                                        struct zwp_text_input_v3 *zwp_text_input_v3,
                                        uint32_t before_length, uint32_t after_length) {
  fprintf(stderr, "delete_surrounding_text before=%d adfter=%d\n",
          before_length,after_length);
}


void text_input_done(void *data, struct zwp_text_input_v3 *zwp_text_input_v3,
                     uint32_t serial) {
//puts("text_input_done");
  struct wl_surface *current_surface = (struct wl_surface*)data;
  const bool bad_event = (serial != commit_serial);
  if ((pending_pre_edit == NULL && current_pre_edit == NULL) ||
      (pending_pre_edit && current_pre_edit && strcmp(pending_pre_edit, current_pre_edit) == 0)) {
      free(pending_pre_edit); pending_pre_edit = NULL;
  } else {
      free(current_pre_edit);
      current_pre_edit = pending_pre_edit;
      pending_pre_edit = NULL;
      if (current_pre_edit) {
        send_text_to_fltk(current_pre_edit, !bad_event, current_surface);
      } else {
        send_text_to_fltk(NULL, false, current_surface);
      }
  }
  if (pending_commit) {
    send_text_to_fltk(pending_commit, false, current_surface);
    free(pending_commit); pending_commit = NULL;
  }
}


static const struct zwp_text_input_v3_listener text_input_listener = {
  .enter = text_input_enter,
  .leave = text_input_leave,
  .preedit_string = text_input_preedit_string,
  .commit_string = text_input_commit_string,
  .delete_surrounding_text = text_input_delete_surrounding_text,
  .done = text_input_done,
};


void Fl_Wayland_Screen_Driver::enable_im() {
  if (text_input_base && !seat->text_input) {
    seat->text_input = zwp_text_input_manager_v3_get_text_input(text_input_base,
                                                                seat->wl_seat);
    //printf("seat->text_input=%p\n",seat->text_input);
    zwp_text_input_v3_add_listener(seat->text_input, &text_input_listener, NULL);
  }
}


void Fl_Wayland_Screen_Driver::disable_im() {
  if (seat->text_input) {
    zwp_text_input_v3_disable(seat->text_input);
    zwp_text_input_v3_commit(seat->text_input);
    zwp_text_input_v3_destroy(seat->text_input);
    seat->text_input = NULL;
    free(pending_pre_edit); pending_pre_edit = NULL;
    free(current_pre_edit); current_pre_edit = NULL;
    free(pending_commit); pending_commit = NULL;
  }
}


static void seat_capabilities(void *data, struct wl_seat *wl_seat, uint32_t capabilities)
{
  struct Fl_Wayland_Screen_Driver::seat *seat =
    (struct Fl_Wayland_Screen_Driver::seat*)data;
  if ((capabilities & WL_SEAT_CAPABILITY_POINTER) && !seat->wl_pointer) {
    seat->wl_pointer = wl_seat_get_pointer(wl_seat);
    wl_pointer_add_listener(seat->wl_pointer, &pointer_listener, seat);
    seat->pointer_scale = 1;
    init_cursors(seat);
  } else if (!(capabilities & WL_SEAT_CAPABILITY_POINTER) && seat->wl_pointer) {
    wl_pointer_release(seat->wl_pointer);
    seat->wl_pointer = NULL;
  }

  bool have_keyboard = seat->xkb_context && (capabilities & WL_SEAT_CAPABILITY_KEYBOARD);
  if (have_keyboard && seat->wl_keyboard == NULL) {
          seat->wl_keyboard = wl_seat_get_keyboard(wl_seat);
          wl_keyboard_add_listener(seat->wl_keyboard,
                          &wl_keyboard_listener, seat);
//fprintf(stderr, "wl_keyboard version=%d\n", wl_keyboard_get_version(seat->wl_keyboard));

  } else if (!have_keyboard && seat->wl_keyboard != NULL) {
          wl_keyboard_release(seat->wl_keyboard);
          seat->wl_keyboard = NULL;
  }
  Fl_Wayland_Screen_Driver *scr_driver = (Fl_Wayland_Screen_Driver*)Fl::screen_driver();
  scr_driver->enable_im();
}


static void seat_name(void *data, struct wl_seat *wl_seat, const char *name) {
  struct Fl_Wayland_Screen_Driver::seat *seat = (struct Fl_Wayland_Screen_Driver::seat*)data;
  seat->name = strdup(name);
}


static struct wl_seat_listener seat_listener = {
  seat_capabilities,
  seat_name
};


static void output_geometry(void *data,
    struct wl_output *wl_output,
    int32_t x,
    int32_t y,
    int32_t physical_width,
    int32_t physical_height,
    int32_t subpixel,
    const char *make,
    const char *model,
    int32_t transform)
{
  //fprintf(stderr, "output_geometry: x=%d y=%d physical=%dx%d\n",x,y,physical_width,physical_height);
  Fl_Wayland_Screen_Driver::output *output = (Fl_Wayland_Screen_Driver::output*)data;
  output->x = int(x);
  output->y = int(y);
  output->dpi = 96; // to elaborate
}


static void output_mode(void *data, struct wl_output *wl_output, uint32_t flags,
      int32_t width, int32_t height, int32_t refresh)
{
  Fl_Wayland_Screen_Driver::output *output = (Fl_Wayland_Screen_Driver::output*)data;
  output->pixel_width = int(width);
  output->pixel_height = int(height);
  output->width = output->pixel_width; // until further notice
  output->height = output->pixel_height;
//fprintf(stderr, "output_mode: [%p]=%dx%d\n",output->wl_output,width,height);
}


static void output_done(void *data, struct wl_output *wl_output)
{
  // Runs at startup and when desktop scale factor is changed or screen added
  Fl_Wayland_Screen_Driver::output *output = (Fl_Wayland_Screen_Driver::output*)data;
//fprintf(stderr, "output_done output=%p\n",output);
  Fl_X *xp = Fl_X::first;
  while (xp) { // all mapped windows
    struct wld_window *win = (struct wld_window*)xp->xid;
    Fl_Window *W = win->fl_win;
    if (win->buffer || W->as_gl_window()) {
      if (W->as_gl_window()) {
        wl_surface_set_buffer_scale(win->wl_surface, output->wld_scale);
        Fl_Window_Driver::driver(W)->is_a_rescale(true);
        W->resize(W->x(), W->y(), W->w(), W->h());
        Fl_Window_Driver::driver(W)->is_a_rescale(false);
      } else {
        Fl_Wayland_Graphics_Driver::buffer_release(win);
      }
      W->redraw();
      Fl_Window_Driver::driver(W)->flush();
    }
    xp = xp->next;
  }
  output->done = true;

  Fl_Wayland_Screen_Driver *scr_driver = (Fl_Wayland_Screen_Driver*)Fl::screen_driver();
  if (scr_driver->screen_count_get() > 0) { // true when output_done runs after initial screen dectection
    scr_driver->screen_count_set( wl_list_length(&(scr_driver->outputs)) );
    scr_driver->init_workarea();
  }
}


static void output_scale(void *data, struct wl_output *wl_output, int32_t factor) {
  Fl_Wayland_Screen_Driver::output *output = (Fl_Wayland_Screen_Driver::output*)data;
  output->wld_scale = factor;
//fprintf(stderr,"output_scale: wl_output=%p factor=%d\n",wl_output, factor);
  // rescale cursors of windows that map here and have a custom cursor
  Fl_Window *win = Fl::first_window();
  while (win) {
    struct wld_window *xid = fl_wl_xid(win);
    struct Fl_Wayland_Window_Driver::surface_output *s_output;
    // get 1st screen where window appears
    s_output = wl_container_of(xid->outputs.next, s_output, link);
    if (xid->custom_cursor && output == s_output->output) {
      Fl_Wayland_Window_Driver *driver = Fl_Wayland_Window_Driver::driver(win);
      driver->set_cursor_4args(xid->custom_cursor->rgb,
                               xid->custom_cursor->hotx, xid->custom_cursor->hoty, false);
    };
    win = Fl::next_window(win);
  }
}


static struct wl_output_listener output_listener = {
  output_geometry,
  output_mode,
  output_done,
  output_scale
};


// Notice: adding use of unstable protocol "XDG output" would allow FLTK to be notified
// in real time of changes to the relative location of multiple displays;
// with the present code, that information is received at startup only.
static void registry_handle_global(void *user_data, struct wl_registry *wl_registry,
           uint32_t id, const char *interface, uint32_t version) {
//fprintf(stderr, "interface=%s version=%u\n", interface, version);
  Fl_Wayland_Screen_Driver *scr_driver = (Fl_Wayland_Screen_Driver*)Fl::screen_driver();
  if (strcmp(interface, "wl_compositor") == 0) {
    if (version < 4) {
      Fl::fatal("wl_compositor version >= 4 required");
    }
    scr_driver->wl_compositor = (struct wl_compositor*)wl_registry_bind(wl_registry,
           id, &wl_compositor_interface, 4);

  } else if (strcmp(interface, "wl_subcompositor") == 0) {
    scr_driver->wl_subcompositor = (struct wl_subcompositor*)wl_registry_bind(wl_registry,
           id, &wl_subcompositor_interface, 1);

  } else if (strcmp(interface, "wl_shm") == 0) {
    scr_driver->wl_shm = (struct wl_shm*)wl_registry_bind(wl_registry,
            id, &wl_shm_interface, 1);

  } else if (strcmp(interface, "wl_seat") == 0) {
    if (version < 3) {
      Fl::fatal("%s version 3 required but only version %i is available\n",
                interface, version);
    }
    if (!scr_driver->seat) scr_driver->seat =
      (struct Fl_Wayland_Screen_Driver::seat*)calloc(1,
          sizeof(struct Fl_Wayland_Screen_Driver::seat));
//fprintf(stderr, "registry_handle_global: seat=%p\n", scr_driver->seat);
    wl_list_init(&scr_driver->seat->pointer_outputs);
    scr_driver->seat->wl_seat = (wl_seat*)wl_registry_bind(wl_registry, id,
                                                           &wl_seat_interface, 3);
    scr_driver->seat->xkb_context = xkb_context_new(XKB_CONTEXT_NO_FLAGS);
    if (scr_driver->seat->xkb_context) {
      const char *locale = getenv("LC_ALL");
      if (!locale || !*locale)
        locale = getenv("LC_CTYPE");
      if (!locale || !*locale)
        locale = getenv("LANG");
      if (!locale || !*locale)
        locale = "C";
      struct xkb_compose_table *table =
        xkb_compose_table_new_from_locale(scr_driver->seat->xkb_context, locale,
                                          XKB_COMPOSE_COMPILE_NO_FLAGS);
      if (table) {
        scr_driver->seat->xkb_compose_state =
          xkb_compose_state_new(table, XKB_COMPOSE_STATE_NO_FLAGS);
      }
    }
    wl_seat_add_listener(scr_driver->seat->wl_seat, &seat_listener, scr_driver->seat);
    if (scr_driver->seat->data_device_manager) {
      scr_driver->seat->data_device =
        wl_data_device_manager_get_data_device(scr_driver->seat->data_device_manager,
                                               scr_driver->seat->wl_seat);
      wl_data_device_add_listener(scr_driver->seat->data_device,
                                  Fl_Wayland_Screen_Driver::p_data_device_listener, NULL);
    }

  } else if (strcmp(interface, wl_data_device_manager_interface.name) == 0) {
    if (!scr_driver->seat) scr_driver->seat =
      (struct Fl_Wayland_Screen_Driver::seat*)calloc(1,
              sizeof(struct Fl_Wayland_Screen_Driver::seat));
    scr_driver->seat->data_device_manager =
      (struct wl_data_device_manager*)wl_registry_bind(wl_registry, id,
                                                       &wl_data_device_manager_interface,
                                                       fl_min(version, 3));
    if (scr_driver->seat->wl_seat) {
      scr_driver->seat->data_device =
        wl_data_device_manager_get_data_device(scr_driver->seat->data_device_manager,
                                               scr_driver->seat->wl_seat);
      wl_data_device_add_listener(scr_driver->seat->data_device,
                                  Fl_Wayland_Screen_Driver::p_data_device_listener, NULL);
    }
//fprintf(stderr, "registry_handle_global: %s\n", interface);

  } else if (strcmp(interface, "wl_output") == 0) {
    if (version < 2) {
      Fl::fatal("%s version 2 required but only version %i is available\n",
                interface, version);
    }
    Fl_Wayland_Screen_Driver::output *output =
      (Fl_Wayland_Screen_Driver::output*)calloc(1, sizeof *output);
    output->id = id;
    output->wld_scale = 1;
#ifdef WL_OUTPUT_RELEASE_SINCE_VERSION
    const int used_version = WL_OUTPUT_RELEASE_SINCE_VERSION;
#else
    const int used_version = 2;
#endif
    output->wl_output = (struct wl_output*)wl_registry_bind(wl_registry,
                 id, &wl_output_interface, fl_min(used_version, version));
    output->gui_scale = 1.f;
    wl_proxy_set_tag((struct wl_proxy *) output->wl_output, &proxy_tag);
    wl_output_add_listener(output->wl_output, &output_listener, output);
    // Put new screen in list of screens, but make sure it's not in list already
    // which may occur after having removed a screen.
    bool found = false;
    Fl_Wayland_Screen_Driver::output *elt;
    wl_list_for_each(elt, &scr_driver->outputs, link) {
      if (elt == output) found = true;
    }
    if (!found) { // add to end of the linked list of displays
      struct wl_list *e = &scr_driver->outputs;
      while (e->next != &scr_driver->outputs) e = e->next; // move e to end of linked list
      wl_list_insert(e, &output->link);
    }
//fprintf(stderr, "wl_output: id=%d wl_output=%p \n", id, output->wl_output);

  } else if (strcmp(interface, xdg_wm_base_interface.name) == 0) {
//fprintf(stderr, "registry_handle_global interface=%s\n", interface);
    scr_driver->xdg_wm_base = (struct xdg_wm_base *)wl_registry_bind(wl_registry, id,
                                                        &xdg_wm_base_interface, 1);
    xdg_wm_base_add_listener(scr_driver->xdg_wm_base, &xdg_wm_base_listener, NULL);
  } else if (strcmp(interface, "gtk_shell1") == 0) {
    Fl_Wayland_Screen_Driver::compositor = Fl_Wayland_Screen_Driver::MUTTER;
    //fprintf(stderr, "Running the Mutter compositor\n");
    scr_driver->seat->gtk_shell = (struct gtk_shell1*)wl_registry_bind(wl_registry, id,
                                  &gtk_shell1_interface, version);
  } else if (strcmp(interface, "weston_desktop_shell") == 0) {
    Fl_Wayland_Screen_Driver::compositor = Fl_Wayland_Screen_Driver::WESTON;
    //fprintf(stderr, "Running the Weston compositor\n");
  } else if (strcmp(interface, "org_kde_plasma_shell") == 0) {
    Fl_Wayland_Screen_Driver::compositor = Fl_Wayland_Screen_Driver::KWIN;
    //fprintf(stderr, "Running the KWin compositor\n");
  } else if (strncmp(interface, "zowl_mach_ipc", 13) == 0) {
    Fl_Wayland_Screen_Driver::compositor = Fl_Wayland_Screen_Driver::OWL;
    //fprintf(stderr, "Running the Owl compositor\n");
    if (wl_list_length(&scr_driver->outputs) == 0) {
      Fl_Wayland_Screen_Driver::output *output =
        (Fl_Wayland_Screen_Driver::output*)calloc(1, sizeof *output);
      output->id = 1;
      output->wld_scale = 1;
      output->gui_scale = 1.f;
      output->width = 1440; output->height = 900;
      output->pixel_width = 1440; output->pixel_height = 900;
      output->done = true;
      wl_list_insert(&(scr_driver->outputs), &output->link);
      scr_driver->screen_count_set(1);
    }
  } else if (strcmp(interface, zwp_text_input_manager_v3_interface.name) == 0) {
    scr_driver->text_input_base = (struct zwp_text_input_manager_v3 *)
      wl_registry_bind(wl_registry, id, &zwp_text_input_manager_v3_interface, 1);
//printf("scr_driver->text_input_base=%p version=%d\n",scr_driver->text_input_base,version);
  }
}


static void registry_handle_global_remove(void *data, struct wl_registry *registry, uint32_t name) {
  Fl_Wayland_Screen_Driver::output *output;
//fprintf(stderr, "registry_handle_global_remove data=%p id=%u\n", data, name);
  Fl_Wayland_Screen_Driver *scr_driver = (Fl_Wayland_Screen_Driver*)Fl::screen_driver();
  bool has_removed_screen = false;
  wl_list_for_each(output, &(scr_driver->outputs), link) { // all screens
    if (output->id == name) { // the screen being removed
      wl_list_remove(&output->link);
      wl_output_destroy(output->wl_output);
      free(output);
      has_removed_screen = true;
      break;
    }
  }
  if (has_removed_screen) {
    scr_driver->screen_count_set( wl_list_length(&(scr_driver->outputs)) );
    scr_driver->init_workarea();
  }
}


static const struct wl_registry_listener registry_listener = {
  registry_handle_global,
  registry_handle_global_remove
};


extern int fl_send_system_handlers(void *);


static void wayland_socket_callback(int fd, struct wl_display *display) {
  if (fl_send_system_handlers(NULL)) return;
  struct pollfd fds = (struct pollfd) { fd, POLLIN, 0 };
  do {
    if (wl_display_dispatch(display) == -1) {
      int err = wl_display_get_error(display);
      if (err == EPROTO) {
        const struct wl_interface *interface;
        int code = wl_display_get_protocol_error(display, &interface, NULL);
        Fl::fatal("Fatal error no %d in Wayland protocol: %s", code, interface->name);
      } else {
        Fl::fatal("Fatal error while communicating with the Wayland server: %s",
                  strerror(errno));
      }
    }
  }
  while (poll(&fds, 1, 0) > 0);
}


Fl_Wayland_Screen_Driver::Fl_Wayland_Screen_Driver() : Fl_Unix_Screen_Driver() {
  libdecor_context = NULL;
  seat = NULL;
  text_input_base = NULL;
  reset_cursor();
  wl_registry = NULL;
}


static void sync_done(void *data, struct wl_callback *cb, uint32_t time) {
  // runs after all calls to registry_handle_global()
  *(struct wl_callback **)data = NULL;
  wl_callback_destroy(cb);
  // keep processing until output_done() has run for each screen
  Fl_Wayland_Screen_Driver *scr_driver = (Fl_Wayland_Screen_Driver*)Fl::screen_driver();
  Fl_Wayland_Screen_Driver::output *output;
  wl_list_for_each(output, &scr_driver->outputs, link) { // each screen of the system
    while (!output->done) wl_display_dispatch(Fl_Wayland_Screen_Driver::wl_display);
  }
  // Now all screens have been initialized
  scr_driver->screen_count_set( wl_list_length(&(scr_driver->outputs)) );
  if (scr_driver->seat) try_update_cursor(scr_driver->seat);
  if (Fl_Wayland_Screen_Driver::compositor != Fl_Wayland_Screen_Driver::OWL) scr_driver->init_workarea();
}


static const struct wl_callback_listener sync_listener = {
  sync_done
};


static void do_atexit() {
  if (Fl_Wayland_Screen_Driver::wl_display) {
    wl_display_roundtrip(Fl_Wayland_Screen_Driver::wl_display);
  }
}


void Fl_Wayland_Screen_Driver::open_display_platform() {
  static bool beenHereDoneThat = false;
  if (beenHereDoneThat)
    return;

  beenHereDoneThat = true;

  if (!wl_display) {
    wl_display = wl_display_connect(NULL);
    if (!wl_display) {
      Fl::fatal("No Wayland connection\n");
    }
  }
  //puts("Using Wayland backend");
  wl_list_init(&outputs);

  wl_registry = wl_display_get_registry(wl_display);
  wl_registry_add_listener(wl_registry, &registry_listener, NULL);
  struct wl_callback *registry_cb = wl_display_sync(wl_display);
  wl_callback_add_listener(registry_cb, &sync_listener, &registry_cb);
  while (registry_cb) wl_display_dispatch(wl_display);
  Fl::add_fd(wl_display_get_fd(wl_display), FL_READ, (Fl_FD_Handler)wayland_socket_callback,
             wl_display);
  fl_create_print_window();
  /* This is useful to avoid crash of the Wayland compositor after
   FLTK apps terminate in certain situations:
   - gnome-shell version < 44 (e.g. version 42.9)
   - focus set to "follow-mouse"
   See issue #821 for details.
  */
  atexit(do_atexit);
}


void Fl_Wayland_Screen_Driver::close_display() {
  if (!Fl_Wayland_Screen_Driver::wl_display) return;
  wl_display_roundtrip(Fl_Wayland_Screen_Driver::wl_display);
  if (text_input_base) {
    disable_im();
    zwp_text_input_manager_v3_destroy(text_input_base);
    text_input_base = NULL;
  }
  while (wl_list_length(&outputs) > 0) {
    Fl_Wayland_Screen_Driver::output *output;
    wl_list_for_each(output, &outputs, link) {
      wl_list_remove(&output->link);
      screen_count_set( wl_list_length(&outputs) );
      if (output->wl_output) {
#ifdef WL_OUTPUT_RELEASE_SINCE_VERSION
        if (wl_output_get_version(output->wl_output) >= WL_OUTPUT_RELEASE_SINCE_VERSION)
          wl_output_release(output->wl_output);
        else
#endif
          wl_output_destroy(output->wl_output);
      }
      free(output);
      break;
    }
  }
  wl_subcompositor_destroy(wl_subcompositor); wl_subcompositor = NULL;
  wl_surface_destroy(seat->cursor_surface); seat->cursor_surface = NULL;
  if (seat->cursor_theme) {
    wl_cursor_theme_destroy(seat->cursor_theme);
    seat->cursor_theme = NULL;
  }
  wl_compositor_destroy(wl_compositor); wl_compositor = NULL;
  // wl_shm-related data
  if (Fl_Wayland_Graphics_Driver::current_pool) {
    struct Fl_Wayland_Graphics_Driver::wld_shm_pool_data *pool_data =
    (struct Fl_Wayland_Graphics_Driver::wld_shm_pool_data*)
    wl_shm_pool_get_user_data(Fl_Wayland_Graphics_Driver::current_pool);
    wl_shm_pool_destroy(Fl_Wayland_Graphics_Driver::current_pool);
    Fl_Wayland_Graphics_Driver::current_pool = NULL;
    /*int err = */munmap(pool_data->pool_memory, pool_data->pool_size);
    //printf("close_display munmap(%p)->%d\n", pool_data->pool_memory, err);
    free(pool_data);
  }
  wl_shm_destroy(wl_shm); wl_shm = NULL;
  if (seat->wl_keyboard) {
    if (seat->xkb_state) {
      xkb_state_unref(seat->xkb_state);
      seat->xkb_state = NULL;
    }
    if (seat->xkb_keymap) {
      xkb_keymap_unref(seat->xkb_keymap);
      seat->xkb_keymap = NULL;
    }
    wl_keyboard_destroy(seat->wl_keyboard);
    seat->wl_keyboard = NULL;
  }
  wl_pointer_destroy(seat->wl_pointer); seat->wl_pointer = NULL;
  if (seat->xkb_compose_state) {
    xkb_compose_state_unref(seat->xkb_compose_state);
    seat->xkb_compose_state = NULL;
  }
  if (seat->xkb_context) {
    xkb_context_unref(seat->xkb_context);
    seat->xkb_context = NULL;
  }
  if (seat->data_source) {
    wl_data_source_destroy(seat->data_source);
    seat->data_source = NULL;
  }
  wl_data_device_destroy(seat->data_device); seat->data_device = NULL;
  wl_data_device_manager_destroy(seat->data_device_manager);
  seat->data_device_manager = NULL;
  wl_seat_destroy(seat->wl_seat); seat->wl_seat = NULL;
  if (seat->name) free(seat->name);
  free(seat); seat = NULL;
  if (libdecor_context) {
    libdecor_unref(libdecor_context);
    libdecor_context = NULL;
  }
  xdg_wm_base_destroy(xdg_wm_base); xdg_wm_base = NULL;
  Fl_Wayland_Plugin *plugin = Fl_Wayland_Window_Driver::gl_plugin();
  if (plugin) plugin->terminate();

  Fl::remove_fd(wl_display_get_fd(Fl_Wayland_Screen_Driver::wl_display));
  wl_registry_destroy(wl_registry); wl_registry = NULL;
  wl_display_disconnect(Fl_Wayland_Screen_Driver::wl_display);
  Fl_Wayland_Screen_Driver::wl_display = NULL;
  delete Fl_Display_Device::display_device()->driver();
  delete Fl_Display_Device::display_device();
  delete Fl::system_driver();
  delete this;
}


struct pair_s { int W, H; };
static void xdg_toplevel_configure(void *data, struct xdg_toplevel *xdg_toplevel,
                                   int32_t width, int32_t height, struct wl_array *states)
{
  struct pair_s *pair = (struct pair_s*)data;
  pair->W = width;
  pair->H = height;
}

static const struct xdg_toplevel_listener xdg_toplevel_listener = {
  .configure = xdg_toplevel_configure,
};

static void xdg_surface_configure(void *data, struct xdg_surface *xdg_surface, uint32_t serial)
{
  xdg_surface_ack_configure(xdg_surface, serial);
}

static const struct xdg_surface_listener xdg_surface_listener = {
    .configure = xdg_surface_configure,
};

static bool compute_full_and_maximized_areas(Fl_Wayland_Screen_Driver::output *output,
                                             int& Wfullscreen, int& Hfullscreen,
                                             int& Wworkarea, int& Hworkarea) {
  if (Fl_Wayland_Screen_Driver::compositor == Fl_Wayland_Screen_Driver::unspecified) {
    Wfullscreen = 0;
    return false;
  }
  bool found_workarea = false;
  Fl_Wayland_Screen_Driver *scr_driver = (Fl_Wayland_Screen_Driver*)Fl::screen_driver();
  struct wl_surface *wl_surface = wl_compositor_create_surface(scr_driver->wl_compositor);
  wl_surface_set_opaque_region(wl_surface, NULL);
  struct xdg_surface *xdg_surface = xdg_wm_base_get_xdg_surface(scr_driver->xdg_wm_base, wl_surface);
  xdg_surface_add_listener(xdg_surface, &xdg_surface_listener, NULL);
  struct xdg_toplevel *xdg_toplevel = xdg_surface_get_toplevel(xdg_surface);
  struct pair_s pair = {0, -1};
  xdg_toplevel_add_listener(xdg_toplevel, &xdg_toplevel_listener, &pair);
  xdg_toplevel_set_fullscreen(xdg_toplevel, output->wl_output);
  wl_surface_commit(wl_surface);
  while (pair.H < 0) wl_display_dispatch(Fl_Wayland_Screen_Driver::wl_display);
  pair.H = -1;
  xdg_toplevel_set_fullscreen(xdg_toplevel, output->wl_output);
  wl_surface_commit(wl_surface);
  while (pair.H < 0) wl_display_dispatch(Fl_Wayland_Screen_Driver::wl_display);
  Wfullscreen = pair.W;
  Hfullscreen = pair.H;
  if (Wfullscreen && Hfullscreen && (Fl_Wayland_Screen_Driver::compositor == Fl_Wayland_Screen_Driver::MUTTER ||
                                     wl_list_length(&scr_driver->outputs) == 1)) {
    struct wl_surface *wl_surface2 = wl_compositor_create_surface(scr_driver->wl_compositor);
    struct xdg_surface *xdg_surface2 = xdg_wm_base_get_xdg_surface(scr_driver->xdg_wm_base, wl_surface2);
    struct xdg_toplevel *xdg_toplevel2 = xdg_surface_get_toplevel(xdg_surface2);
    struct pair_s pair2 = {0, -1};
    xdg_toplevel_add_listener(xdg_toplevel2, &xdg_toplevel_listener, &pair2);
    xdg_toplevel_set_parent(xdg_toplevel2, xdg_toplevel);
    xdg_toplevel_set_maximized(xdg_toplevel2);
    pair2.H = -1;
    wl_surface_commit(wl_surface2);
    while (pair2.H < 0) wl_display_dispatch(Fl_Wayland_Screen_Driver::wl_display);
    Wworkarea = pair2.W;
    Hworkarea = pair2.H;
    xdg_toplevel_destroy(xdg_toplevel2);
    xdg_surface_destroy(xdg_surface2);
    wl_surface_destroy(wl_surface2);
    if (Wworkarea == Wfullscreen && Hworkarea < Hfullscreen && Hworkarea > Hfullscreen - 80)
      found_workarea = true;
  } else {
    Wworkarea = Wfullscreen;
    Hworkarea = Hfullscreen;
  }
  xdg_toplevel_destroy(xdg_toplevel);
  xdg_surface_destroy(xdg_surface);
  wl_surface_destroy(wl_surface);
  /*int fractional_scale = int(100 * (output->pixel_width / float(Wfullscreen)));
  printf("fullscreen=%dx%d workarea=%dx%d  fractional_scale=%d%%  wld_s=%d\n",
         Wfullscreen,Hfullscreen,Wworkarea,Hworkarea,fractional_scale,output->wld_scale);*/
  return found_workarea;
}

static int workarea_xywh[4] = { -1, -1, -1, -1 };


/* Implementation note about computing work area and about handling fractional scaling.
 
 FLTK computes 2 pairs of (WxH) values for each display:
 1) (pixel_width x pixel_height) gives the size in pixel of a display. It's unchanged by
 any scaling applied by the compositor; it's assigned by function output_mode().
 2) (width x height) gives the size in pixels of a buffer that would fully cover the display.
 When the active scaling is non-fractional, these equations hold:
   pixel_width = width = wld_scale * configured-width-of-fullscreen-window
   pixel_height = height = wld_scale * configured-height-of-fullscreen-window
 
 When fractional scaling is active, buffers received from client are scaled down
 by the compositor and mapped to screen. These equations hold:
   pixel_width < width = wld_scale * configured-width-of-fullscreen-window
   pixel_height < height = wld_scale * configured-height-of-fullscreen-window

 One way for a client to discover that fractional scaling is active on a given display
 is to ask for a fullscreen window on that display, get its configured size and compare
 it to that display's pixel size. That's what function compute_full_and_maximized_areas() does.
 
 One way for a client to discover the work area size of a display is to get the configured size
 of a maximized window on that display. FLTK didn't find a way to control in general
 on what display the compositor puts a maximized window. One procedure which works
 under Mutter or with a single display was found. In this procedure, we create first a fullscreen
 window on a given display and then we create a maximized window made a child of the
 fullscreen one. Under mutter, this puts reliably the maximized window on the same
 display as the fullscreen one, giving the size of that display's work area.
 Therefore, FLTK computes an exact work area size only with MUTTER or when the system
 contains a single display. That's also done by function compute_full_and_maximized_areas().
 
 The procedure to compute the work area size also reveals which display is primary:
 that with a work area vertically smaller than the display's pixel height. This allows
 to place the primary display as FLTK display #0. Again, FLTK guarantees to identify
 the primary display only under MUTTER.
 */

void Fl_Wayland_Screen_Driver::init_workarea()
{
  wl_display_roundtrip(Fl_Wayland_Screen_Driver::wl_display); // important after screen removal
  Fl_Wayland_Screen_Driver::output *output, *mainscreen = NULL;
  wl_list_for_each(output, &outputs, link) {
    int Wfullscreen, Hfullscreen, Wworkarea, Hworkarea;
    bool found_workarea = compute_full_and_maximized_areas(output, Wfullscreen, Hfullscreen, Wworkarea, Hworkarea);
    if (found_workarea && !mainscreen) {
      mainscreen = output;
    } else found_workarea = false;
    if (Wfullscreen && Hfullscreen) { // skip sway which puts 0 there
      output->width = Wfullscreen * output->wld_scale; // pixels
      output->height = Hfullscreen * output->wld_scale; // pixels
      if (found_workarea) {
        workarea_xywh[0] = output->x; // pixels
        workarea_xywh[1] = output->y; // pixels
        workarea_xywh[2] = Wworkarea * output->wld_scale; // pixels
        workarea_xywh[3] = Hworkarea * output->wld_scale; // pixels
      }
    }
  }
  if (mainscreen) { // put mainscreen first in list of screens
    wl_list_remove(&mainscreen->link);
    wl_list_insert(&outputs, &mainscreen->link);
  } else {
    wl_list_for_each(output, &outputs, link) { // find first screen in list
      workarea_xywh[0] = output->x; // pixels
      workarea_xywh[1] = output->y; // pixels
      workarea_xywh[2] = output->width; // pixels
      workarea_xywh[3] = output->height; // pixels
      break;
    }
  }
  Fl::handle(FL_SCREEN_CONFIGURATION_CHANGED, NULL);
}


int Fl_Wayland_Screen_Driver::x() {
  if (!Fl_Wayland_Screen_Driver::wl_registry) open_display();
  Fl_Wayland_Screen_Driver::output *output;
  wl_list_for_each(output, &outputs, link) {
    break;
  }
  return workarea_xywh[0] / (output->gui_scale * output->wld_scale);
}


int Fl_Wayland_Screen_Driver::y() {
  if (!Fl_Wayland_Screen_Driver::wl_registry) open_display();
  Fl_Wayland_Screen_Driver::output *output;
  wl_list_for_each(output, &outputs, link) {
    break;
  }
  return workarea_xywh[1] / (output->gui_scale * output->wld_scale);
}


int Fl_Wayland_Screen_Driver::w() {
  if (!Fl_Wayland_Screen_Driver::wl_registry) open_display();
  Fl_Wayland_Screen_Driver::output *output;
  wl_list_for_each(output, &outputs, link) {
    break;
  }
  return workarea_xywh[2] / (output->gui_scale * output->wld_scale);
}


int Fl_Wayland_Screen_Driver::h() {
  if (!Fl_Wayland_Screen_Driver::wl_registry) open_display();
  Fl_Wayland_Screen_Driver::output *output;
  wl_list_for_each(output, &outputs, link) {
    break;
  }
  return workarea_xywh[3] / (output->gui_scale * output->wld_scale);
}


void Fl_Wayland_Screen_Driver::init() {
  if (!Fl_Wayland_Screen_Driver::wl_registry) open_display();
}


void Fl_Wayland_Screen_Driver::screen_work_area(int &X, int &Y, int &W, int &H, int n)
{
  if (num_screens < 0) init();
  if (n < 0 || n >= num_screens) n = 0;
  if (n == 0) { // for the main screen, these return the work area
    X = Fl::x();
    Y = Fl::y();
    W = Fl::w();
    H = Fl::h();
  } else { // for other screens, work area is full screen,
    screen_xywh(X, Y, W, H, n);
  }
}


void Fl_Wayland_Screen_Driver::screen_xywh(int &X, int &Y, int &W, int &H, int n)
{
  if (num_screens < 0) init();

  if ((n < 0) || (n >= num_screens))
    n = 0;

  if (num_screens > 0) {
    Fl_Wayland_Screen_Driver::output *output;
    int i = 0;
    wl_list_for_each(output, &outputs, link) {
      if (i++ == n) { // n'th screen of the system
        float s = output->gui_scale * output->wld_scale;
        X = output->x / s;
        Y = output->y / s;
        W = output->width / s;
        H = output->height / s;
        break;
      }
    }
  }
}


void Fl_Wayland_Screen_Driver::screen_dpi(float &h, float &v, int n)
{
  if (num_screens < 0) init();
  h = v = 0.0f;

  if (n >= 0 && n < num_screens) {
    Fl_Wayland_Screen_Driver::output *output;
    int i = 0;
    wl_list_for_each(output, &outputs, link) {
      if (i++ == n) { // n'th screen of the system
        h = output->dpi;
        v = output->dpi;
        break;
      }
    }
  }
}


// Implements fl_beep(). See documentation in src/fl_ask.cxx.
void Fl_Wayland_Screen_Driver::beep(int type)
{
  fprintf(stderr, "\007");
}


void Fl_Wayland_Screen_Driver::flush()
{
  if (Fl_Wayland_Screen_Driver::wl_display) {
    wl_display_flush(Fl_Wayland_Screen_Driver::wl_display);
  }
}


extern void fl_fix_focus(); // in Fl.cxx


void Fl_Wayland_Screen_Driver::grab(Fl_Window* win)
{
  if (win) {
    if (!Fl::grab()) {
    }
    Fl::grab_ = win;    // FIXME: Fl::grab_ "should be private", but we need
                        // a way to *set* the variable from the driver!
  } else {
    if (Fl::grab()) {
      // We must keep the grab in the non-EWMH fullscreen case
      Fl::grab_ = 0;    // FIXME: Fl::grab_ "should be private", but we need
                        // a way to *set* the variable from the driver!
      fl_fix_focus();
    }
  }
}


static void set_selection_color(uchar r, uchar g, uchar b)
{
  Fl::set_color(FL_SELECTION_COLOR,r,g,b);
}


static void getsyscolor(const char *key1, const char* key2, const char *arg,
                        const char *defarg, void (*func)(uchar,uchar,uchar)) {
  uchar r, g, b;
  if (!arg) arg = defarg;
  if (!Fl::screen_driver()->parse_color(arg, r, g, b))
    Fl::error("Unknown color: %s", arg);
  else
    func(r, g, b);
}


void Fl_Wayland_Screen_Driver::get_system_colors()
{
  open_display();
  const char* key1 = 0;
  if (Fl::first_window()) key1 = Fl::first_window()->xclass();
  if (!key1) key1 = "fltk";
  if (!bg2_set)
    getsyscolor("Text","background",    fl_bg2, "#ffffff", Fl::background2);
  if (!fg_set)
    getsyscolor(key1,  "foreground",    fl_fg,  "#000000", Fl::foreground);
  if (!bg_set)
    getsyscolor(key1,  "background",    fl_bg,  "#c0c0c0", Fl::background);
  getsyscolor("Text", "selectBackground", 0, "#000080", set_selection_color);
}


Fl_RGB_Image *Fl_Wayland_Screen_Driver::read_win_rectangle(int X, int Y, int w, int h,
                                                           Fl_Window *win,
                                                           bool ignore, bool *p_ignore) {
  struct wld_window* xid = win ? fl_wl_xid(win) : NULL;
  if (win && (!xid || !xid->buffer)) return NULL;
  struct Fl_Wayland_Graphics_Driver::draw_buffer *buffer;
  if (win) buffer = &xid->buffer->draw_buffer;
  else {
    Fl_Image_Surface_Driver *dr = (Fl_Image_Surface_Driver*)Fl_Surface_Device::surface();
    buffer = Fl_Wayland_Graphics_Driver::offscreen_buffer(
                                              dr->image_surface()->offscreen());
  }
  float s = win ?
    Fl_Wayland_Window_Driver::driver(win)->wld_scale() * scale(win->screen_num()) :
                  Fl_Surface_Device::surface()->driver()->scale();
  int Xs, Ys, ws, hs;
  if (s == 1) {
    Xs = X; Ys = Y; ws = w; hs = h;
  } else {
    Xs = Fl_Scalable_Graphics_Driver::floor(X, s);
    Ys = Fl_Scalable_Graphics_Driver::floor(Y, s);
    ws = Fl_Scalable_Graphics_Driver::floor(X+w, s) - Xs;
    hs = Fl_Scalable_Graphics_Driver::floor(Y+h, s) - Ys;
  }
  if (ws == 0 || hs == 0) return NULL;
  uchar *data = new uchar[ws * hs * 3];
  uchar *p = data, *q;
  for (int j = 0; j < hs; j++) {
    q = buffer->buffer + (j+Ys) * buffer->stride + 4 * Xs;
    for (int i = 0; i < ws; i++) {
      *p++ = *(q+2); // R
      *p++ = *(q+1); // G
      *p++ = *q;     // B
      q += 4;
    }
  }
  Fl_RGB_Image *rgb = new Fl_RGB_Image(data, ws, hs, 3);
  rgb->alloc_array = 1;
  return rgb;
}


void Fl_Wayland_Screen_Driver::offscreen_size(Fl_Offscreen off_, int &width, int &height)
{
  struct Fl_Wayland_Graphics_Driver::draw_buffer *off = Fl_Wayland_Graphics_Driver::offscreen_buffer(off_);
  width = off->width;
  height = off->data_size / off->stride;
}


float Fl_Wayland_Screen_Driver::scale(int n) {
  Fl_Wayland_Screen_Driver::output *output;
  int i = 0;
  wl_list_for_each(output, &outputs, link) {
    if (i++ == n) break;
  }
  return output->gui_scale;
}


void Fl_Wayland_Screen_Driver::scale(int n, float f) {
  Fl_Wayland_Screen_Driver::output *output;
  int i = 0;
  wl_list_for_each(output, &outputs, link) {
    if (i++ == n) {
      output->gui_scale = f;
      return;
    }
  }
}


void Fl_Wayland_Screen_Driver::set_cursor() {
  do_set_cursor(seat);
}


struct wl_cursor *Fl_Wayland_Screen_Driver::default_cursor() {
  return seat->default_cursor;
}


void Fl_Wayland_Screen_Driver::default_cursor(struct wl_cursor *cursor) {
  seat->default_cursor = cursor;
  do_set_cursor(seat);
}


struct wl_cursor *Fl_Wayland_Screen_Driver::cache_cursor(const char *cursor_name) {
  return wl_cursor_theme_get_cursor(seat->cursor_theme, cursor_name);
}


void Fl_Wayland_Screen_Driver::reset_cursor() {
  for (int i = 0; i < cursor_count; i++) xc_cursor[i] = NULL;
}


uint32_t Fl_Wayland_Screen_Driver::get_serial() {
  return seat->serial;
}


struct wl_seat*Fl_Wayland_Screen_Driver::get_wl_seat() {
  return seat->wl_seat;
}


char *Fl_Wayland_Screen_Driver::get_seat_name() {
  return seat->name;
}


struct xkb_keymap *Fl_Wayland_Screen_Driver::get_xkb_keymap() {
  return seat->xkb_keymap;
}


int Fl_Wayland_Screen_Driver::get_mouse(int &xx, int &yy) {
  open_display();
  xx = Fl::e_x_root; yy = Fl::e_y_root;
  if (!seat->pointer_focus) return 0;
  Fl_Window *win = Fl_Wayland_Window_Driver::surface_to_window(seat->pointer_focus);
  if (!win) return 0;
  int snum = Fl_Window_Driver::driver(win)->screen_num();
//printf("get_mouse(%dx%d)->%d\n", xx, yy, snum);
  return snum;
}


void Fl_Wayland_Screen_Driver::set_spot(int font, int height, int x, int y, int w, int h, Fl_Window *win) {
  Fl_Wayland_Screen_Driver::insertion_point_location(x, y, height);
}


void Fl_Wayland_Screen_Driver::reset_spot() {
  Fl::compose_state = 0;
  Fl_Wayland_Screen_Driver::next_marked_length = 0;
  Fl_Wayland_Screen_Driver::insertion_point_location_is_valid = false;
}


void Fl_Wayland_Screen_Driver::display(const char *d)
{
  if (d && !wl_registry) { // if display was opened, it's too late
    if (wl_display) {
      // only the wl_display_connect() call was done, redo it because the target
      // Wayland compositor may be different
      wl_display_disconnect(wl_display);
    }
    wl_display = wl_display_connect(d);
    if (!wl_display) {
      fprintf(stderr, "Error: '%s' is not an active Wayland socket\n", d);
      exit(1);
    }
  }
}


void *Fl_Wayland_Screen_Driver::control_maximize_button(void *data) {
  // The code below aims at removing the calling window's fullscreen button
  // while dialog runs. Unfortunately, it doesn't work with some X11 window managers
  // (e.g., KDE, xfce) because the button goes away but doesn't come back,
  // so we move this code to a virtual member function.
  // Noticeably, this code works OK under Wayland.
  struct win_dims {
    Fl_Widget_Tracker *tracker;
    int minw, minh, maxw, maxh;
    struct win_dims *next;
  };

  if (!data) { // this call turns each decorated window's maximize button off
    struct win_dims *first_dim = NULL;
    // consider all bordered, top-level FLTK windows
    Fl_Window *win = Fl::first_window();
    while (win) {
      if (!win->parent() && win->border() &&
          !( ((struct wld_window*)Fl_X::flx(win)->xid)->state &
            LIBDECOR_WINDOW_STATE_MAXIMIZED) ) {
        win_dims *dim = new win_dims;
        dim->tracker = new Fl_Widget_Tracker(win);
        win->get_size_range(&dim->minw, &dim->minh, &dim->maxw, &dim->maxh, NULL, NULL, NULL);
        //make win un-resizable
        win->size_range(win->w(), win->h(), win->w(), win->h());
        dim->next = first_dim;
        first_dim = dim;
      }
      win = Fl::next_window(win);
    }
    return first_dim;
  } else { // this call returns each decorated window's maximize button to its previous state
    win_dims *first_dim = (win_dims *)data;
    while (first_dim) {
      win_dims *dim = first_dim;
      //give back win its resizing parameters
      if (dim->tracker->exists()) {
        Fl_Window *win = (Fl_Window*)dim->tracker->widget();
        win->size_range(dim->minw, dim->minh, dim->maxw, dim->maxh);
      }
      first_dim = dim->next;
      delete dim->tracker;
      delete dim;
    }
    return NULL;
  }
}


int Fl_Wayland_Screen_Driver::poll_or_select_with_delay(double time_to_wait) {
  if (wl_display_dispatch_pending(wl_display) > 0) return 1;
  return Fl_Unix_Screen_Driver::poll_or_select_with_delay(time_to_wait);
}


// like Fl_Wayland_Screen_Driver::poll_or_select_with_delay(0.0) except no callbacks are done:
int Fl_Wayland_Screen_Driver::poll_or_select() {
  int ret = wl_display_prepare_read(wl_display);
  if (ret == 0) wl_display_cancel_read(wl_display);
  else return 1;
  return Fl_Unix_Screen_Driver::poll_or_select();
}


int Fl_Wayland_Screen_Driver::event_key(int k) {
  if (k >= 'A' && k <= 'Z') k += 32;
  return (search_int_vector(key_vector, k) >= 0);
}


int Fl_Wayland_Screen_Driver::get_key(int k) {
  return event_key(k);
}


float Fl_Wayland_Screen_Driver::base_scale(int numscreen) {
  const char *p;
  float factor = 1;
  if ((p = fl_getenv("FLTK_SCALING_FACTOR"))) {
    sscanf(p, "%f", &factor);
  }
  return factor;
}


struct wl_display *fl_wl_display() {
  return Fl_Wayland_Screen_Driver::wl_display;
}