bug#27647: 26.0.50; Line numbers implemented natively disappear momentarily when frame out of focus

[Eli Zaretskii]

> Date: Mon, 13 Nov 2017 19:45:40 +0100
> From: martin rudalics <rudalics@gmx.at>
> CC: npostavs@users.sourceforge.net, agrambot@gmail.com, 
>  27647@debbugs.gnu.org, kaushal.modi@gmail.com
> 
>  > Not exactly.  tip_frame should be nil when GTK pops a native tooltip,
>  > then tip_frame will get its simple semantics back.
> 
> x_hide_tip uses NILP (tip_frame) to decide whether to hide the tip.

That's non-GTK code which GTK doesn't need, but left it alone.  The
whole GTK support in x_hide_tip is patched over the non-GTK code, with
dirty tricks like setting tip_frame to nil just to bypass the non-GTK
part of the function.  We will be better off with a separate GTK-only
implementation.

> IIUC GTK doesn't need the original frame.

xg_hide_tooltip needs it, because the GTK tooltip widget is stashed
away in its output->data.x structure.

> But it sets tooltip_frame to it so Fx_show_tip and friends can base
> their decisions on it.  Look at occurrences of FRAMEP (tip_frame)
> and FRAME_LIVE_P (XFRAME (tip_frame)).  They pass because for GTK
> tip_frame is a live frame associated with the tooltip.  Jan tried
> hard to leave the native tooltip code untouched.

Once again, it would be better to have the GTK code completely
separated, IMO.