The language input chooser is being created and destroyed every time
it is opened and closed. This is noticeably slow and is hardly
necessary as the values it contains should not change.
To fix this, these changes reuse the same instance of the input chooser
(by hiding and showing it) instead of renewing it.
The input chooser is also now shown using gtk_dialog_run to avoid having
it destroyed from the default delete event.
These changes prevent warnings when unreferencing the default input
source, locale and back rows which are never instanced by some locales
(and thus null).
The language input chooser is being leaked. The reason for the leak
is a "circular reference": the input chooser keeps a GtkBuilder
instance that gets destroyed when the chooser is, itself, destroyed.
However, the input chooser is never destroyed because the GtkBuilder
instance keeps a reference to it.
These changes dismiss the GtkBuilder once it is no longer needed in the
input chooser which fixes the leak.
Since we can't export IBus sources through the localed API we
shouldn't even allow users to choose them.
This allows us to stop having to show an apologising dialog which
makes us look a bit bad and was using deprecated gtk+ API that we're
trying to get rid of. Instead, we show the same information up front,
in the input chooser.
https://bugzilla.gnome.org/show_bug.cgi?id=740986
gnome_parse_locale() can return an empty country_code for some locales,
which we are not taking into account when building the simple_locale
string.
https://bugzilla.gnome.org/show_bug.cgi?id=738963
Selecting and pressing the Add button continues to work but this
should streamline the the input chooser dialog for mouse users by
making it possible to add by double clicking a row.
https://bugzilla.gnome.org/show_bug.cgi?id=732720
Acting on every keystroke makes the UI sluggish given the number of
widgets we have so let's rate limit this to a reasonable frequency
that still feels responsive.
https://bugzilla.gnome.org/show_bug.cgi?id=695466
