Re: fix for readline terminal size problems when window is resized with open pager

On Wed, Dec 16, 2015 at 1:29 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> I did some more experimentation and concluded that actually, this problem
> has nothing whatsoever to do with pager invocations. What seems to really
> be happening is that libreadline activates its SIGWINCH handler only while
> it's being called to collect input, which is fine in itself, but *it does
> not notice screen resizes that happen when the handler is not active*.
>
> You can prove this by doing, say, "select pg_sleep(10);" and resizing
> the window before the backend comes back. Readline never notices the
> resize, even though no pager invocation happens at all.
>
> So I now think that print.c shouldn't be involved at all, and the right
> thing to do is just have gets_interactive() invoke the resize function
> immediately before calling readline(). That will still leave a window
> for SIGWINCH to be missed, but it's a pretty tiny one.

right -- agreed.

> And somebody oughta report this as a libreadline bug ...

See https://bugs.python.org/issue23735 for background. Apparently
this is expected behavior (and we are far from the only ones
complaining about it):

"And so we reach where we are. If a SIGWINCH arrives while readline is
not active, and the application using callback mode does not catch it and
tell readline about the updated screen dimensions (rl_set_screen_size()
exists for this purpose), readline will not know about the new size."

merlin