Shared keybindings

[Claes at work]

> The bottom line is that I think keys need to be configurable to suit
> different environments and user habits. Deciding that some common key
> combination MUST always be used for this and that will always create
> new problems for someone I believe.

I also believe keys needs to be configurable, but I would prefer not
remapping single conflicting keys in individual applications. It would
be better if "modifier keyspaces" could be assigned, to avoid
conflicting behaviour between WM/Application/legacy keybindings. Such
modifiers could have standardized symbolic names, which are mapped to
physical keys separately.

For example, the modifier key for application shortcuts would not be
tightly coupled to Control. Perhaps toolkits and applications could
check the environment for a specific environment variable to see what
key should be used as the application "command" modifier (name
borrowed from Mac here) , and if it is undefined, settle on Control_L
or Control_R as default?

So setting "COMMAND_MODIFIER=Control_L||Control_R" would give current
behaviour, and setting "COMMAND_MODIFIER=Super_L||Super_R" would give
"non-conflicting" behaviour, using the Win key. On Mac hardware it
could be mapped to whatever the Mac control key returns, and if you
have Sun hardware, you can use something else.

It may seem like a bad idea to introduce more configurability, but I
see this suggestion mostly as a transition mechanism. If such a check
was built into software from now on, perhaps in two years time it
would give a consistent behaviour if this variable was changed?

Claes