Moving the focus off a client window

[Sam Spilsbury <smspillaz gmail com>]

Hi,

I was doing some work on Unity the other day and noticed an
interesting problem - we have a situation where we need to keep a
window mapped but at some points remove its input shape or move it
offscreen. At this point, it makes no sense for that window to keep
the input focus, but it doesn't seem like there's a model in the ICCCM
or EWMH for handling the case where a client wants to remove its input
focus without explicitly setting the input focus to something else
(which is wrong).

I'd like to be able to have some kind of protocol to handle this case,
and initially I thought that maybe I could change the input hint on
the client window to FALSE and then send a synthetic FocusIn event to
the client window, at which point the window manager would receive
that and move the focus off to something else since that window is not
allowed to be focussed. However, the ICCCM is vague on this point, and
says that where WM_TAKE_FOCUS is not present in WM_PROTOCOLS and
InputHint is FALSE in WM_HINTS then the window has "No Input - The
client never expects keyboard input. An example would be xload or
another output-only client. ". However, it does not state what should
happen should the client explicitly request input focus, which is what
is going on here. I would imagine in this case that should a client
request input focus to a window that does not allow input, that the
window manager should focus the next appropriate window, whether that
be a transient window, an ancestor, a group member or the next most
active window.

What does everyone think of something like the following:

 * Client changes InputHint to false and removes WM_TAKE_FOCUS from WM_PROTOCOLS
 * Client sends a synthetic FocusIn event to its own window with the
window member being set to the client, mode being NotifyNormal and
detail being NotifyDetailNone
 * WM gets the FocusIn event on the client window, sees that InputHint
is false, moves the focus off to the next appropriate window.

Regards,

Sam

-- 
Sam Spilsbury