screen header, similar to the status bar. Hide the welcome body if the
message stack length is > 0. Use this to display the "Waiting for
capture input data..." message when we're capturing from a pipe. This
lets the user know what's going on and keeps them from clicking on a
welcome screen item while we're waiting for data to arrive. You can see
this in action by running
(sleep 5; cat /path/to/a/capture) | wireshark -k -i -
svn path=/trunk/; revision=28196