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From: garyo@THINK.COM (Gary Oberbrunner)
Newsgroups: comp.windows.x
Subject: Re: R4 xterm modmap strangeness
Message-ID: <9001112348.AA17091@prometheus.think.com>
Date: 11 Jan 90 23:48:54 GMT
References: <9001112030.AA06475@expire.lcs.mit.edu>
Sender: daemon@athena.mit.edu (Mr Background)
Organization: The Internet
Lines: 48


    I ask:
        Why should I have to change the keysyms in my xmodmap just to change
        the modifier bits associated with some keys?

Bob replies:    
    Because of the way "Meta" is defined.  It isn't defined by "a key that
    has Meta on it", it's defined by "a modifier bit that has an associated
    key that has Meta on it".  For better or worse (the Xt spec is probably
    too liberal) the control modifier is included in this search, so it
    gets treated as both control and meta simultaneously.  At least I think
    that's what's going on.

I know it's just me, but I still don't fully get it.  The Xt doc on this
(finally found it!) says something like this:

Meta is defined by "ANY (???) modifier bit whose corresponding keycode
(what if there are >1?)  contains the corresponding left or right keysym
(Meta_L or Meta_R, I guess)."

Isn't this extremely strange?  Is my interpretation right?  Was it really
like this in R3?
How does this work in practice (and where is it done in the source)?
And why is this in the Xt spec anyway?  Shouldn't this all be in the red
book?  I'd expect this stuff to be defined with XLookupString.  No wonder I
couldn't find it!
    
        Is this because I have two physical keys with the same keysym
        (Control_L)?
    
    Yes, xmodmap only adds the first key that it finds with the specified
    keysym, not all keys.  You should have figured this out from the
    keycode values that xmodmap prints out (in parens).  You'll have to
    stand on your head a bit to fix this; xmodmap is stupid and only
    accepts keysyms in the add command.  You'll have to first label the key
    with some unique keysym, then do the add, then change the keysym to
    Control.

Clearly here you're saying that the keysym is not used to look up the
modifier bits at run time.  This jibes with the Xt doc, which says that
Shift, Lock and Control are treated specially - they just look at the
modifier map, not the keysym.  Why are they different?

				- Gary Oberbrunner
				Thinking Machines Corporation
				245 First St
				Cambridge, MA 02142
				garyo@think.com