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# postghost.tcl - Ghost a menu item at post time.

# Copyright (C) 1997 Cygnus Solutions.

# Written by Tom Tromey <tromey@cygnus.com>.

# Helper proc.

proc GHOST_helper {menu index predicate} {

  if {[eval $predicate]} then {

    set state normal

  } else {

    set state disabled

  }

  $menu entryconfigure $index -state $state

}

# Add a -postcommand to a menu.  This is careful not to stomp other

# postcommands.

proc add_post_command {menu callback} {

  set old [$menu cget -postcommand]

  # We use a "\n" and not a ";" to separate so that people can put

  # comments into their -postcommands without fear.

  $menu configure -postcommand "$old\n$callback"

}

# Run this to make a menu item which ghosts or unghosts depending on a

# predicate that is run at menu-post time.  The NO_CACHE option

# prevents the index from being looked up statically; this is useful

# if you want to use an entry name as the index and you have a very

# dynamic menu (ie one where the numeric index of a named item is not

# constant over time).  If PREDICATE returns 0 at post time, then the

# item will be ghosted.

proc ghosting_menu_item {menu index predicate {no_cache 0}} {

  if {! $no_cache} then {

    set index [$menu index $index]

  }

  add_post_command $menu [list GHOST_helper $menu $index $predicate]

}