bug#21473: 24.5; very slow tooltip display to sort-of-slow remote display

[Ken Raeburn <raeburn@permabit.com>]

Eli Zaretskii <eliz@gnu.org> writes:

> Is there something new in what you discovered, given the fact that a
> tooltip is just a special kind of frame, and so everything that you
> reported which causes slow creation of a new frame pertains also to
> tooltips?

Some of it, yes.

Some of this is similar to stuff that I dug up looking into #11822, but
which wasn't the "unneeded work on other frames" issue where I thought
we wanted to keep the focus for #11822, hence the separate filing. But
in this case, most of the X network exchanges appear to be just about
the new frame, so the fix for #11822 Stefan proposed doesn't look like
it should affect this.

While the tooltip is a kind of frame, its creation is handled
differently from a regular X frame, which may be why it seems to
side-step the additional other-frame work seen in #11822.

The heavy use of XSync calls are something I hadn't looked into before,
also.

Ken