Re: Emacs's set-frame-size can not work well with gnome-shell?

[martin rudalics <rudalics@gmx.at>]

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 > But anyway, the second patch is equivalent to my workaround
 > (hiding/showing the frame), so it doesn't seem strictly necessary. The
 > downside is the same: flickering.

That's what I wanted to know - whether the flickering is just the same
as with your Lisp solution.

 > I guess the only part that could be
 > improved there is to avoid resizing (and flicker) if the target size
 > stays the same.

We could try that.

 > Another thing: judging by the file names, at least, that change in the
 > behavior would also affect the gtk2 build. But it's already working
 > fine. We certainly don't want to introduce flickering on resize to it.

Hiding is controlled by 'x-gtk-hide-child-frame-during-resize' which you
can toggle at any time during a session.

 > To clarify: would you consider the patch #1 for inclusion in Emacs 27?

Not in its present form.  I attach another variant based on a variable
'x-resize-child-frame-special'.  But I cannot test it any more because
since yesterday mutter --replace crashes here with

mutter[1053]: segfault at 88 ip 00007fe0cd3f05f5 sp 00007ffdb7e46470 error 6 in libmutter-3.so.0.0.0[7fe0cd3ba000+db000]

so that patch likely needs tweaking (if it works at all).

martin

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diff --git a/src/gtkutil.c b/src/gtkutil.c
index 6308c38f16..a77810141a 100644
--- a/src/gtkutil.c
+++ b/src/gtkutil.c
@@ -997,12 +997,13 @@ xg_frame_set_char_size (struct frame *f, int width, int height)
     }
   else
     {
+      GdkWindow *gwin = gtk_widget_get_window (FRAME_GTK_OUTER_WIDGET (f));
+
       frame_size_history_add
 	(f, Qxg_frame_set_char_size_3, width, height,
 	 list2i (totalwidth, totalheight));

-      gtk_window_resize (GTK_WINDOW (FRAME_GTK_OUTER_WIDGET (f)),
-			 totalwidth, totalheight);
+      gdk_window_resize (gwin, (gint)totalwidth, (gint)totalheight);
       fullscreen = Qnil;
     }

diff --git a/src/xfns.c b/src/xfns.c
index 276ea1c393..cfe4e7a2c0 100644
--- a/src/xfns.c
+++ b/src/xfns.c
@@ -4125,6 +4125,9 @@ DEFUN ("x-create-frame", Fx_create_frame, Sx_create_frame,
   x_wm_set_size_hint (f, window_prompting, false);
   unblock_input ();

+  if (FRAME_PARENT_FRAME (f) && x_resize_child_frame_special)
+    adjust_frame_size (f, 1000, 1000, 0, true, Qx_create_frame_2);
+
   adjust_frame_size (f, FRAME_TEXT_WIDTH (f), FRAME_TEXT_HEIGHT (f),
 		     0, true, Qx_create_frame_2);

diff --git a/src/xterm.c b/src/xterm.c
index 21d99f0c7b..84b154f8fc 100644
--- a/src/xterm.c
+++ b/src/xterm.c
@@ -8953,6 +8953,23 @@ handle_one_xevent (struct x_display_info *dpyinfo,
 #ifdef USE_CAIRO
 	  x_cr_update_surface_desired_size (f, configureEvent.xconfigure.width,
 					    configureEvent.xconfigure.height);
+#endif
+          f = 0;
+        }
+      else if (f && FRAME_PARENT_FRAME (f)
+	       && x_resize_child_frame_special
+	       && (configureEvent.xconfigure.width != FRAME_PIXEL_WIDTH (f)
+		   || configureEvent.xconfigure.height != FRAME_PIXEL_HEIGHT (f)))
+        {
+          block_input ();
+          if (FRAME_X_DOUBLE_BUFFERED_P (f))
+            font_drop_xrender_surfaces (f);
+          unblock_input ();
+          xg_frame_resized (f, configureEvent.xconfigure.width,
+                            configureEvent.xconfigure.height);
+#ifdef USE_CAIRO
+	  x_cr_update_surface_desired_size (f, configureEvent.xconfigure.width,
+					    configureEvent.xconfigure.height);
 #endif
           f = 0;
         }
@@ -13747,4 +13764,10 @@ syms_of_xterm (void)
 consuming frame position adjustments.  In newer versions of GTK, Emacs
 always uses gtk_window_move and ignores the value of this variable.  */);
   x_gtk_use_window_move = true;
+
+  DEFVAR_BOOL ("x-resize-child-frame-special", x_resize_child_frame_special,
+    doc: /* Non-nil means treat child frames specially during resizing.
+Set this if and only if your window manager refuses to resize child
+frames as expected.  */);
+  x_resize_child_frame_special = false;
 }