#!/bin/sh
 # execute in wish from path \
 exec wish "$0" ${1+"$@"}

 # clipserver.tcl - Keeps an eye on everything that is copied to the clipboard 
 #                      and doesn't let it disappear in the ether if the 
 #                      application it was copied from exits.
 #
 # Author: Luciano Espirito Santo 
 #
 # More on the purpose of this program:
 # In Linux, when we copy text from an application and close that application, 
 # we often lose that content. It is no longer available to be pasted 
 # elsewhere. That can easily become a nightmare if you're used to Windows' 
 # clipboard because in that OS clipboard content does not evaporate when we 
 # close an application. The content remains faithfully available to all and 
 # sundry until something else is copied and replaces it.
 # This program watches all changes that occur in the system's clipboard and 
 # retains the content so it never gets lost until something else is copied.
 # 
 # Calling it a "server" may be an exaggeration, but extending this code 
 # would be a simple task. One could even transmit the clipboard content 
 # over a network or sockets, if one can find an actual use for that.
 # 
 # Post edit: now it strikes me that perhaps I should have called it
 # "A little clipboard daemon". Too bad we can't rename wikit pages. :-(
 # 
 # History 
 # 
 #      Version 1.0     2005-02-24      Luciano Espirito Santo
 #      First version. Alpha stage.
 #
 #      Version 1.01    2005-02-28      Michael Kirkham
 #      Improved with "hash bang" line method suggested at https://wiki.tcl-lang.org/812.
 #
 #
 #      KNOWN ISSUES: 
 #      It will work in Windows too, but Windows users simply don't need it.
 #      This program offers no guarantees! Use it at your own risk!
 #
 #      TO DO: 
 #      - Update this code. The version I actually run on my desktop
 #        nowadays (October 2009) is quite different, and it needs a 
 #        fair amount of adjustment before it can be shared.
 #
 #      LICENSE: BSD
 #
 # How to use it:
 # 
 # Just run it with wish. It has to be wish, not tclsh. Keep it running all 
 # the time. Suggestion: run it from KDE's Autostart folder in your home 
 # directory. It runs invisibly. No window or widget is displayed.

 # ================================================
 # PROCS 
 # packages: none 
 # {refresh clipboard}: the single proc and core of this application 
 # ================================================
 
 # proc 1 of 1
 proc {refresh clipboard} {}     {
 global myClip1  myClip2

        # Sometimes the clipboard contains something else other than text and 
        # that causes an error. In that case, we trap the error and assign to 
        # myClip1 the value of myClip2, because myClip2 always has a copy of the 
        # last valid content.

        if  { [ catch { set myClip1 [ selection get -selection CLIPBOARD ] } myError ] !=0 } { 
            set  myClip1  $myClip2 
        }

        # If myClip1 is not empty, i.e. received "good" content from myClip2, or 
        # even better, found new valid content by itself, we put that good 
        # content into myClip2, so that myClip2 always has the newest valid 
        # content. If the clipboard receives bad content and myClip1 chokes in 
        # the next iteration, myClip2 will come to the rescue.

        if  { $myClip1  !=  "" }        {
            set  myClip2  $myClip1
        }

        # myClip2 always has the good content. Let's force it into the clipboard. 
        # This is the part that makes sure the content isn't lost if the 
        # application that provided it exits.

        clipboard  clear  -displayof   .
        clipboard  append  -displayof  .  $myClip2
 
        # And here is how we poll (update) the clipboard every 600 milliseconds

        after  600  [ list {refresh clipboard} ]
 
 }
 
 # ================================================
 # run the program
 # ================================================

 catch { destroy .clipserver errorswindow }
 set w [ toplevel .clipserver ]
 wm  withdraw  .
 wm  withdraw  $::w
 wm  title  $::w  "clipboard server"
 tk  appname  "clipboard server"
 
 set  myClip1  ""
 set  myClip2  ""
 
 {refresh clipboard}