Created attachment 756043 [details]
weird-behaviour-of-preedit-in-ibus-typing-booster.ogv

$ rpm -q ibus-typing-booster
ibus-typing-booster-0.0.31-1.fc18.noarch
mfabian@ari:~
$ 

Typed chars     Visible in preëdit
g               g
r               gr
u               gru
"               grü
n               grün
BACKSPACE       grü
BACKSPACE       gr
BACKSPACE       g
a               gra

See attached video.

The problem is, that characters are removed inconsistently from the
input buffer and the transliterated string in the preëdit.  I.e.  the
3 times BACKSPACE removed the “rün” from the preëdit, but “u"n”
was removed from the typed chars, leaving “gr” in the list of typed
chars. Then, when typing the final “a”, the “r” from the list of
typed chars comes back into the preëdit.

Leads to very confusing and inconsistent behaviour which depends on
length differences in the input and the transliteration.

On top of that, there is code for handling arrow left, arrow right,
delete, control arrow left, ... but all these do nothing useful
currently in the preëdit, some of them just cause error messages to
appear in the debug log file.