Fix full-screen code when there is no window manager (Bug#21317)

* src/xterm.h (x_wm_supports): Declare external.
* src/xterm.c (wm_suppports): Rename to `x_wm_supports', export.
(do_ewmh_fullscreen, x_ewmh_activate_frame): Adjust for rename.
(x_check_fullscreen): Call `x_wm_set_size_hint', restore
`fullscreen' frame parameter.
* gtkutil.c (x_wm_set_size_hint): Set size hints when running
without a window manager.

Copyright-paperwork-exempt: yes

src/gtkutil.c

@@ -1375,7 +1375,9 @@ x_wm_set_size_hint (struct frame *f, long int flags, bool user_position)
 
   XSETFRAME (frame, f);
   fs_state = Fframe_parameter (frame, Qfullscreen);
-  if (EQ (fs_state, Qmaximized) || EQ (fs_state, Qfullboth))
+  if ((EQ (fs_state, Qmaximized) || EQ (fs_state, Qfullboth)) &&
+      (x_wm_supports (f, FRAME_DISPLAY_INFO (f)->Xatom_net_wm_state) ||
+       x_wm_supports (f, FRAME_DISPLAY_INFO (f)->Xatom_net_wm_state_fullscreen)))
     {
       /* Don't set hints when maximized or fullscreen.  Apparently KWin and
          Gtk3 don't get along and the frame shrinks (!).

src/xterm.c

@@ -9782,8 +9782,8 @@ x_set_offset (struct frame *f, register int xoff, register int yoff, int change_
    Specification/Extended Window Manager Hints at
    http://freedesktop.org/wiki/Specifications/wm-spec.  */
 
-static bool
-wm_supports (struct frame *f, Atom want_atom)
+bool
+x_wm_supports (struct frame *f, Atom want_atom)
 {
   Atom actual_type;
   unsigned long actual_size, bytes_remaining;
@@ -9976,7 +9976,7 @@ static bool
 do_ewmh_fullscreen (struct frame *f)
 {
   struct x_display_info *dpyinfo = FRAME_DISPLAY_INFO (f);
-  bool have_net_atom = wm_supports (f, dpyinfo->Xatom_net_wm_state);
+  bool have_net_atom = x_wm_supports (f, dpyinfo->Xatom_net_wm_state);
   int cur;
   bool dummy;
 
@@ -9985,7 +9985,7 @@ do_ewmh_fullscreen (struct frame *f)
   /* Some window managers don't say they support _NET_WM_STATE, but they do say
      they support _NET_WM_STATE_FULLSCREEN.  Try that also.  */
   if (!have_net_atom)
-    have_net_atom = wm_supports (f, dpyinfo->Xatom_net_wm_state_fullscreen);
+    have_net_atom = x_wm_supports (f, dpyinfo->Xatom_net_wm_state_fullscreen);
 
   if (have_net_atom && cur != f->want_fullscreen)
     {
@@ -10155,6 +10155,8 @@ x_handle_net_wm_state (struct frame *f, const XPropertyEvent *event)
 static void
 x_check_fullscreen (struct frame *f)
 {
+  Lisp_Object lval = Qnil;
+
   if (do_ewmh_fullscreen (f))
     return;
 
@@ -10173,22 +10175,31 @@ x_check_fullscreen (struct frame *f)
       switch (f->want_fullscreen)
         {
           /* No difference between these two when there is no WM */
-        case FULLSCREEN_BOTH:
         case FULLSCREEN_MAXIMIZED:
+          lval = Qmaximized;
+          width = x_display_pixel_width (dpyinfo);
+          height = x_display_pixel_height (dpyinfo);
+          break;
+        case FULLSCREEN_BOTH:
+          lval = Qfullboth;
           width = x_display_pixel_width (dpyinfo);
           height = x_display_pixel_height (dpyinfo);
           break;
         case FULLSCREEN_WIDTH:
+          lval = Qfullwidth;
           width = x_display_pixel_width (dpyinfo);
 	  height = height + FRAME_MENUBAR_HEIGHT (f);
 	  break;
         case FULLSCREEN_HEIGHT:
+          lval = Qfullheight;
           height = x_display_pixel_height (dpyinfo);
         }
 
       frame_size_history_add
 	(f, Qx_check_fullscreen, width, height, Qnil);
 
+      x_wm_set_size_hint (f, 0, false);
+
       XResizeWindow (FRAME_X_DISPLAY (f), FRAME_OUTER_WINDOW (f),
 		     width, height);
 
@@ -10201,6 +10212,10 @@ x_check_fullscreen (struct frame *f)
 	  x_sync (f);
 	}
     }
+
+  /* `x_net_wm_state' might have reset the fullscreen frame parameter,
+     restore it. */
+  store_frame_param (f, Qfullscreen, lval);
 }
 
 /* This function is called by x_set_offset to determine whether the window
@@ -10564,7 +10579,7 @@ x_ewmh_activate_frame (struct frame *f)
 
   struct x_display_info *dpyinfo = FRAME_DISPLAY_INFO (f);
 
-  if (FRAME_VISIBLE_P (f) && wm_supports (f, dpyinfo->Xatom_net_active_window))
+  if (FRAME_VISIBLE_P (f) && x_wm_supports (f, dpyinfo->Xatom_net_active_window))
     {
       Lisp_Object frame;
       XSETFRAME (frame, f);

src/xterm.h

@@ -1072,6 +1072,7 @@ x_display_set_last_user_time (struct x_display_info *dpyinfo, Time t)
 }
 
 extern void x_set_sticky (struct frame *, Lisp_Object, Lisp_Object);
+extern bool x_wm_supports (struct frame *, Atom);
 extern void x_wait_for_event (struct frame *, int);
 extern void x_clear_under_internal_border (struct frame *f);