bug#18912: 24.4; mode-line corruption on graphical frames in dual-headed display

[Bruno Félix Rezende Ribeiro]

Eli Zaretskii wrote:
> Then try this:
> 
>   (add-hook 'pre-command-hook 'force-mode-line-update)

It doesn't work. :-(

In fact, even

  (add-hook 'pre-command-hook (lambda () (call-process "xrefresh")))

doesn't work completely.

The difference between the two, however, is the fact that while
'force-mode-line-update' has no effect at all, so as one scrolls trough
a buffer the mode-line becomes increasingly corrupt, accumulating over
it the trail of all the lines which were once "below" it --- as if the
mode-line's background was never cleared, the 'xrefresh' command makes
Emacs repaint the mode-line's background so at each scrolling the
mode-line is "cleanly" corrupted by the current buffer's line "below"
it, and only by that one.

-- 
 ,= ,-_-. =.  Bruno Félix Rezende Ribeiro (oitofelix) [0x28D618AF]
((_/)o o(\_)) There is no system but GNU;
 `-'(. .)`-'  GNU Linux-Libre is one of its official kernels;
     \_/      All software must be free as in freedom;

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