Allow specifying a layout for programming and add a key for switching to
it easily.
The switching key is placed on the top edge of the space bar.
The option has no effect by default because the ergonomic isn't ideal,
it needs to be enabled explicitly.
Users of Latin-script languages certainly prefer to use one layout (for
programming or not). This feature might be removed in favor of a better
language-switching mechanisms in the future.
Modifiers can temporarily remove a key from the layout by returning
'null'.
Make sure pointer handling code handle these modified keys gracefully
and doesn't trigger a key event and a vibration for the removed key.
Before sending a key event while modifiers are active, send events for
the modifier keys.
Some applications don't look at the "metaState" flags but instead keep
track of the up and down events for the modifiers.
For example, the basic text views that are in every applications
correctly handle the "metaState" flags except for one binding:
Selecting text with the arrows while pressing shift.
Currently using the diamond symbol like the history meta key: https://en.wikipedia.org/wiki/Meta_key
However, this key is actually interpreted as the Super/Windows key but
Android calls it "meta" internally.
It is placed on the top-right of the enter key on every layouts.
It sends a special event (performEditorAction) instead of writing a
newline.
The "actionId" is passed through the EditorInfo object in an obfuscated
way so it's not clear whether it's using the right one.
