Wayland: dispatch socket data with function libdecor_dispatch() as required by libdecor.

Many thanks to Jonas Ådahl for pointing out FLTK didn't follow this requirement
and suggesting code changes (#1390).

src/drivers/Wayland/Fl_Wayland_Screen_Driver.cxx

@@ -1422,31 +1422,12 @@ static const struct wl_registry_listener registry_listener = {
 };
 
 
-static void wayland_socket_callback(int fd, struct wl_display *display)
+static void libdecor_fd_callback(int fd, struct libdecor *libdecor_context)
 {
-  if (wl_display_prepare_read(display) == -1) {
-    wl_display_dispatch_pending(display);
-    return;
-  }
-  wl_display_flush(display);
-  struct pollfd fds = (struct pollfd) { fd, POLLIN, 0 };
-  if (poll(&fds, 1, 0) <= 0) {
-    wl_display_cancel_read(display);
-    return;
-  }
-  if (fds.revents & (POLLERR | POLLHUP)) {
-    wl_display_cancel_read(display);
-    goto fatal;
-  }
-  if (wl_display_read_events(display) == -1)
-    goto fatal;
-  if (wl_display_dispatch_pending(display) == -1)
-    goto fatal;
-  return;
-fatal:
-  if (wl_display_get_error(display) == EPROTO) {
+  if (libdecor_dispatch(libdecor_context, 0) >= 0) return;
+  if (wl_display_get_error(Fl_Wayland_Screen_Driver::wl_display) == EPROTO) {
     const struct wl_interface *interface;
-    int code = wl_display_get_protocol_error(display, &interface, NULL);
+    int code = wl_display_get_protocol_error(Fl_Wayland_Screen_Driver::wl_display, &interface, NULL);
     Fl::fatal("Fatal error %d in Wayland protocol: %s",
               code, (interface ? interface->name : "unknown") );
   } else {
@@ -1511,6 +1492,16 @@ static void do_atexit() {
 }
 
 
+static void handle_error(struct libdecor *libdecor_context, enum libdecor_error error, const char *message)
+{
+  Fl::fatal("Caught error (%d): %s\n", error, message);
+}
+
+static struct libdecor_interface libdecor_iface = {
+  .error = handle_error,
+};
+
+
 void Fl_Wayland_Screen_Driver::open_display_platform() {
   static bool beenHereDoneThat = false;
   if (beenHereDoneThat)
@@ -1533,8 +1524,9 @@ void Fl_Wayland_Screen_Driver::open_display_platform() {
   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);
+  libdecor_context = libdecor_new(wl_display, &libdecor_iface);
+  Fl::add_fd(libdecor_get_fd(libdecor_context), FL_READ, (Fl_FD_Handler)libdecor_fd_callback,
+             libdecor_context);
   fl_create_print_window();
   /* This is useful to avoid crash of the Wayland compositor after
    FLTK apps terminate in certain situations:
@@ -1621,10 +1613,6 @@ void Fl_Wayland_Screen_Driver::close_display() {
   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();
@@ -1645,7 +1633,11 @@ void Fl_Wayland_Screen_Driver::close_display() {
   }
 #endif // HAVE_CURSOR_SHAPE
 
-  Fl::remove_fd(wl_display_get_fd(Fl_Wayland_Screen_Driver::wl_display));
+  if (libdecor_context) {
+    Fl::remove_fd(libdecor_get_fd(libdecor_context));
+    libdecor_unref(libdecor_context);
+    libdecor_context = NULL;
+  }
   wl_registry_destroy(wl_registry); wl_registry = NULL;
   wl_display_disconnect(Fl_Wayland_Screen_Driver::wl_display);
   Fl_Wayland_Screen_Driver::wl_display = NULL;

src/drivers/Wayland/Fl_Wayland_Window_Driver.cxx

@@ -659,18 +659,6 @@ int Fl_Wayland_Window_Driver::scroll(int src_x, int src_y, int src_w, int src_h,
 }
 
 
-static void handle_error(struct libdecor *libdecor_context, enum libdecor_error error, const char *message)
-{
-  Fl::fatal("Caught error (%d): %s\n", error, message);
-}
-
-
-static struct libdecor_interface libdecor_iface = {
-  .error = handle_error,
-};
-
-
-
 static void delayed_rescale(Fl_Window *win) {
   Fl_Window_Driver::driver(win)->is_a_rescale(true);
   win->size(win->w(), win->h());
@@ -1054,11 +1042,12 @@ void Fl_Wayland_Window_Driver::wait_for_expose()
   Fl_Window_Driver::wait_for_expose();
   struct wld_window * xid = fl_wl_xid(pWindow);
   if (!xid) return;
+  Fl_Wayland_Screen_Driver *scr_driver = (Fl_Wayland_Screen_Driver*)Fl::screen_driver();
   if (pWindow->fullscreen_active()) {
     if (xid->kind == DECORATED) {
       while (!(xid->state & LIBDECOR_WINDOW_STATE_FULLSCREEN) ||
              !(xid->state & LIBDECOR_WINDOW_STATE_ACTIVE)) {
-        wl_display_dispatch(Fl_Wayland_Screen_Driver::wl_display);
+        libdecor_dispatch(scr_driver->libdecor_context, 0);
       }
     } else if (xid->kind == UNFRAMED) {
       wl_display_roundtrip(Fl_Wayland_Screen_Driver::wl_display);
@@ -1066,7 +1055,7 @@ void Fl_Wayland_Window_Driver::wait_for_expose()
   } else if (xid->kind == DECORATED) {
     // necessary for the windowfocus demo program with recent Wayland versions
     if (!(xid->state & LIBDECOR_WINDOW_STATE_ACTIVE)) {
-      wl_display_dispatch(Fl_Wayland_Screen_Driver::wl_display);
+      libdecor_dispatch(scr_driver->libdecor_context, 0);
     }
   }
 }
@@ -1527,9 +1516,6 @@ void Fl_Wayland_Window_Driver::makeWindow()
 
   } else if (pWindow->border() && !pWindow->parent() ) { // a decorated window
     new_window->kind = DECORATED;
-    if (!scr_driver->libdecor_context)
-      scr_driver->libdecor_context = libdecor_new(Fl_Wayland_Screen_Driver::wl_display,
-                                                  &libdecor_iface);
     new_window->frame = libdecor_decorate(scr_driver->libdecor_context, new_window->wl_surface,
                                           &libdecor_frame_iface, new_window);
     // appears in the Gnome desktop menu bar