bug#26742: Display bug with composed strings

[Andreas Schwab]

On Mai 03 2017, YAMAMOTO Mitsuharu <mituharu@math.s.chiba-u.ac.jp> wrote:

>> If I create a file temp.txt containing the following:
>
>> -*- prettify-symbols-alist: (("R_PO" 8477 (Br . cl) 8804)); -*-
>> !!! R_PO !!!
>
>> and run ‘emacs-24.5 -Q temp.txt -f prettify-symbols-mode’, I observe
>> a surprising display bug: when I move the point across the second
>> line, as soon as the point reaches the blank space after “R_PO”, I
>> see a second ℝ displayed instead of the third “!”.
>
> On the Mac port, the filled box cursor disappears if I move it on
> the composite characters.  The patch below seems to work for this
> bug.  Could you try if it also solves the problems you observe?

That fixes the disappearing box cursor, but doesn't fix the ghost
character.

Andreas.

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Andreas Schwab, schwab@linux-m68k.org
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