xclipfrom

#!/usr/bin/wish

# We don't need a visible window.
wm withdraw .

set otherDisplay [lindex $argv 0]
puts "proxying CLIPBOARD from $otherDisplay"

# This gets called when another process tries to paste from our selection.
proc handleSelection {offset maxChars} {
    global otherDisplay
    puts "CLIPBOARD data requested"
    variable result
    # Grab the current clipboard contents from the *other* display.
    # I would rather do this without fork/execing a subprocess, but I
    # couldn't find a way to make tcl/tk talk to two X11 servers at once.
    catch {exec xclip -display $otherDisplay -selection CLIPBOARD -o} result
    return $result
}

# This gets called when we lose ownership of the clipboard, which generally
# means someone cut/copy something on the current display.  We don't want
# to override that, so we exit and leave them alone.  xclipsync can start
# another copy of xclipfrom going in the other direction, from the newly-
# copied data on this display to the now-obsolete clipboard on the other
# display.
proc lostSelection {} {
    puts "lost selection\n"
    exit 0
}

# If we get asked for clipboard data, this is what we provide.
selection handle -selection CLIPBOARD . handleSelection

# Take ownership of the clipboard, so it someone wants to paste, they
# come to us first.  We get called if someone else subsequently takes
# ownership.
selection own -selection CLIPBOARD -command lostSelection .