Re: incorrect handling of invisible characters in prompt string

[Eric Blake]

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This bug is insidious, as there is more than one wrong string printed to
the display.  For example, this screenshot shows that the original prompt
doubles the last prompt character ($), but after tab completion has
displayed a list, it doubles the first user-character (a).  From there,
using the arrow keys to go back, then forward in history, corrects the
display:

$ PS1='\[\e]0;1\a\]$'
$$a[TAB]
a/                     am4tPD2876/            atrace.dll
a2p.exe                amcompat.tlb           attrib.exe
...
alrsvc.dll             atobm.exe
$aa[UP]
$aPS1='\[\e]0;1\a\]$'[DOWN]
$a[UP]
$PS1='\[\e]0;1\a\]$'

Also, someone on the cygwin mailing list suggested that a workaround is to
fake bash into thinking that the last invisible character is the last
prompt character:

PS1='\[\e]0;1\a\]$\[\]'

This solves the problem of the initial prompt, but not the display after
tab-completion.  And it points out a flaw in the readline expand_prompt()
logic for letting a zero-length \[\] invisible character marker pair
change the *lip parameter to an index of a non-invisible character.

- --
Life is short - so eat dessert first!

Eric Blake             ebb9@byu.net
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