[PATCH] protocol: Add DnD actions

[Bill Spitzak]

This is still bothering me as being much too complicated.

I think a list of actions can be sent from the DnD source to the target, 
and the target selects one. There is no need for the compositor to do 
any intersection of the sets and there is no need to communicate the set 
of target actions to the compositor.

Your concerns about shift state being handled by the source are 
misplaced. This would not change at all under what I am proposing, the 
source could still use the shift state to change the list of actions.

My proposal is basically to take yours, and remove the ability for the 
target to send a set of actions that the compositor then interesect with 
the source list. Instead this "intersection" is done by the target, and 
the target sends *one* action (or "none") indicating the result of the 
intersection.

Unless you want the compositor to draw user interface to allow the user 
to choose the action, which seems very much a bad idea, I cannot see 
what your proposal will allow to happen that this simplified version 
would not.

I do believe any kind of popup (like a menu for choosing "move or copy") 
would have to be done by the target. This is because the target may have 
extra actions that the source does not care about or does not know 
about, such as "insert" verses "replace". The popup would grab the 
keyboard focus but when dismissed it may go back to a different client 
than the target.