bug#8874: Redisplay confusion in Info, due to recentering fix

[Chong Yidong]

Eli Zaretskii <eliz@gnu.org> writes:

> How urgent is it to fix this?  Can it be postponed until I'm done with
> bidi reordering of display strings, and we enter code freeze?

The bidi work is more urgent, so feel free to postphone the fix for this
until you have the time.

FWIW, I took a quick look, and it appears that the following should do
the trick.  But it can wait till you have time to double-check the code.

*** src/xdisp.c 2011-06-14 18:57:19 +0000
--- src/xdisp.c 2011-06-18 18:03:55 +0000
***************
*** 14391,14397 ****
              if (pt_offset)
                centering_position -= pt_offset;
              centering_position -=
!               FRAME_LINE_HEIGHT (f) * (1 + margin + (last_line_misfit != 0));
              /* Don't let point enter the scroll margin near top of
                 the window.  */
              if (centering_position < margin * FRAME_LINE_HEIGHT (f))
--- 14391,14397 ----
              if (pt_offset)
                centering_position -= pt_offset;
              centering_position -=
!               FRAME_LINE_HEIGHT (f) * (2 + margin + (last_line_misfit != 0));
              /* Don't let point enter the scroll margin near top of
                 the window.  */
              if (centering_position < margin * FRAME_LINE_HEIGHT (f))