[iPAQ] Button/keycode mapping and handling

Today I was investigating the mapping of the external buttons to key
events in the handhelds.org XServer sources. Currently, the keyboard
driver in the server detects button presses, and translates them into
various key events, using a mix of regular and XFree86 extended
KeySyms. The latest XFree86 sources add a set of KeySyms that
represent "macro" or "system" type keys and buttons found on newer
keyboards and PDAs.

I believe that only the input focus window receives these key events.
That makes sense for the keysyms that map to normal key functions
that applications would expect to receive (Up, Left, Right, and
Down), since you would want the arrow keys to move the cursor around
in a text editing window.

But how are the keysyms that represent system functions, such as
Record, to be handled in a way that is transparent to the window with
the input focus? Presumably you don't want to have to code every
program to know what to do with these special codes.

Is it assumed that it is the responsibility of the window manager to
capture all KeyPress events on all client windows, and filter-out the
extended codes? For example, if the window manager saw an incoming
event containing any of extended codes, it would lookup what to do
(presumably via a resource or config file) the appropriate action,
perform it, and not pass the KeyPress event to the client window. All
other KeySyms would be passed on to the focus application for normal
processing.

Does this make sense (is it even possible?). Or is there some other
method that would work on a global basis that allows for capturing
these events and mapping them to the appropriate function? In the
window managers I've seen, the XSendEvent is used to relay
intercepted events, and this sets the send_event flag in the event.
The downside to this is that I've seen some applications (e.g. xterm
and Tk/TCL) ignore these synthetic events, so this might not allow
the arrow buttons to work with such applications if they are
intercepted by the window manager.

For the LinuxCE MIPS VR41XX X11 environment I've been working with
(which has a /dev/buttons device) I created two daemons. Both monitor
the buttons device, and both have separate config files that tells
each daemon what to do for each button.

The system button daemon is designed to invoke processes, so its
config file maps each button of interest to a Linux command line that
gets invoked. For example, I set it up to invoke a shutdown handler
for the Power button. The Record button might invoke an X record
application. By default, the config file is set up to ignore the
buttons that normally act like keyboard keys.

Conversely, the X button daemon's config file is a button to KeySym
lookup table. The daemon gets the KeySym for the pressed button, and
looks up the KeyCode via the server for the specified KeySym. This
KeyCode is sent to the server via the XTest extension, which in turn
appears to the input focus window as a normal (nonsynthetic) KeyPress
event. The X button handler is designed to handle the buttons that
act like keyboard keys (up, down, enter, etc.), and thus its config
file is set up to ignore the Power, Record, etc. buttons (but could
handle them if desired).

I'm not advocating changing the way the handhelds.org server handles
the buttons, but I'd like to implement the appropriate support for
handling the "system" key events in a way that allows for the user to
remap what function is performed for each button (much like what is
available under WinCE on many devices). I'd like to implement it in a
way that works with the server design, and also doesn't require
changes to regular X11 applications. Suggestions as to the proper way
to do this with the ARM X server would be appreciated! Hopefully I'm
not missing something obvious. :^)

                                                - Merle

-- 
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