We were using g_utf8_strlen() to measure strings for layout, but that
counts combining marks too, and also fails to deal with "fullwidth"
(ie, double-width) CJK characters.
Add a new utility function to do a better job of this (based on code
from vte), and use it everywhere.
Unless NMTUI_DEBUG is set, don't pop up a dialog when a
g_warning/critical/etc occurs. Just hide the main screen briefly so
the error doesn't get printed over the UI, and restore it after; any
messages that get logged will be visible after nmtui exits.
Since we can't align buttons to half-character positions, they end up
looking more random than centered:
| <Add> |
| <Edit...> |
| <Delete> |
So just let them be left-aligned instead. It looks better.
The keyboard focus was getting reset to the first widget any time a
widget changed validity, because the form wasn't updating priv->focus
when it should have.
