bug#17905: 24.3.50; writing with a giant font triggers RTL text entry

[Stefan Monnier <monnier@iro.umontreal.ca>]

> again?  I guess not, in which case this is not about _cursor_
> positioning, but rather about _point_ positioning.  Right?

Exactly.

> Anyway, since Joe complicated the recipe with going full-screen (which
> makes everything dependent on the monitor dimensions), I would ask you
> two to answer the following questions:

> - Can the issue be reproduced without enlarging the font?

I think enlarging the font is necessary because I think an important
element is that there be a partially displayed line.

> - Does the issue happen only in continuation lines?

Yes.

>   If so, does it happen as soon as the line is continued, or do you
>   have to have several continuation lines?

I think the issue shows up when:
- the current logical line starts before window-start.
- point is at the bottom of the window.
- More specifically, point is on the last line and is only
  partially displayed.

I can reproduce it as follows:
- emacs -Q
- C-x C-+
- hit "g" (other chars work as well) and keep it pressed until the
  screen is completely filled with "g"s (window-start should be
  continuation of the current line (there's a little curly arrow in the
  left fringe of every displayed line, including the very first one)),
  at which point the "g"'s keep being inserted but all the same position
  with the cursor (and point) being at the left of the bottom
  (partially-displayed) line.

With just a single C-x C-+, it takes a while to fill the window, so you
can speed it up by using many more C-x C-+ or by making the
window smaller (but do make sure that the window should not be
a whole multiple of lines, so that the last line is partially hidden by
the mode-line).


        Stefan