This mode changes the current IBus engine to ibus-typing-booster
under the rug (i.e. no changes in keyboard status menu) for any
XKB engine selected.
In order to make it useful for the currently selected language,
the typing-booster dictionary is changed to the current XKB
layout language. And since the OSK has its own emoji panel,
typing-boosters own emoji completion is disabled.
These changes only apply as long as the OSK panel is shown,
reverting to the original engine and typing-booster configuration
after it is hidden. This in theory also caters for users that
do have ibus-typing-booster enabled as an input source.
The final effect is text prediction for the language that is
being typed, according to the OSK layout, given that
ibus-typing-booster and the relevant hunspell dictionaries are
used.
Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/2278>
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