Support for high refresh rate monitors

[foxpy]

On a high refresh rate monitor (in @iambeingtracked's case 144hz) the selection GUI doesn't act as smooth as it should act with such a refresh rate.

Supersedes naelstrof/maim#278

[N-R-K]

Likely source of the issue:

slop/src/slop.cpp

Lines 190 to 192 in 864bdb2

	// X11 explodes if we update as fast as possible, here's a tiny sleep.
	XFlush(x11->display);
	std::this_thread::sleep_for(std::chrono::milliseconds(10));

[foxpy]

The XSync function flushes the output buffer and then waits until all requests have been received and processed by the X server.

I think the fix would be to replace

 XFlush(x11->display);
 std::this_thread::sleep_for(std::chrono::milliseconds(10));

with a simple

 XSync(x11->display, False);

CC @naelstrof

[naelstrof]

Yeah that seems like it'll work, someone make a pull request and I'll accept it

[N-R-K]

I'm not sure if XSync the "right" fix here or not. Ideally you'd want to sync with the vblank - using something like XPresent. (But I don't have any first hand experience in doing that, so can't offer anything more atm).

[foxpy]

maybe we should even use XNextEvent. slop is not a videogame, it only has to refresh screen when a new input event arrives.

though I don't have any experience, too.