bug#22637: 25.1.50; `mode-line` face `:height` incompatible with `scroll-conservatively 101`.

[Eli Zaretskii <eliz@gnu.org>]

> Date: Thu, 11 Feb 2016 18:12:57 -0800
> From: Keith David Bershatsky <esq@lawlist.com>
> 
> Setting the `:height` property of the `mode-line` face to 140, and `scroll-conservatively 101`, prevent redisplay from making point fully visible following a large yank of text.

I cannot reproduce this.  I tried some large yanks, including all of
xdisp.c, and the cursor stayed fully visible.

IME, it is sometimes required to make small changes to the default
font, like enlarge it by 1 or 2 pixels, to reproduce problems seen on
other platforms.  I will do that if needed, but please provide a full
recipe, including the text you yanked, and the precise keystrokes used
to yank it: I'd like to be sure I do all the same gestures you did,
before I start playing with font sizes.

> As a suggestion / feature, please consider adding a GLYPH_DEBUG message to indicate when a function from the `timer-idle-list` has triggered a redisplay.

We already have that, albeit in a subtle way: when that happens, you
should see this on stderr:

  redisplay_preserve_echo_area (8)

That "8" part says redisplay_preserve_echo_area was invoked by the
function that ran timers just before that.  You should be able to see
the code which produces that in detect_input_pending_run_timers,
around line 9836 in keyboard.c.

Thanks.