#!/bin/bash

# @file   xmenity
# @author Nat Goodspeed
# @date   2013-01-09
# @brief  Provide progress UI for bash scripts (e.g. update_install) using
#         zenity if available, xmessage if not.
# 
# $LicenseInfo:firstyear=2013&license=viewerlgpl$
# Copyright (c) 2013, Linden Research, Inc.
# $/LicenseInfo$

# This script invokes either zenity --progress or, if zenity is unavailable,
# wraps xmessage in a zenity-like interface. That is its mutant power.
# Pass $1 as the title for your zenity box. It is ignored by xmessage.
# Send updates on stdin:
# A line containing only a decimal integer from 0 - 100 sets that progress.
# End with 100 to tell zenity to terminate.
# A line starting with '#' replaces the progress text.
# All other stdin lines are ignored.

zenpath="$(which zenity)"
if [ -n "$zenpath" -a -x "$zenpath" ]
then # if executable zenity is on PATH, run that instead of this.
     exec "$zenpath" --progress --title="$1" --auto-close --width=320 --height=120
fi

# Arriving here means we don't have zenity available. The remainder of this
# script is the xmessage wrapper.

# We operate by leaving one background xmessage process running. This is the
# pid of that process.
xmpid=""

function clear_message {
    [ -n "$xmpid" ] && kill $xmpid
    xmpid=""
}

# Cancel any pending xmessage, regardless of how we exit.
trap 'clear_message' EXIT

while read line
do # terminate like zenity --progress
   [ "$line" == "100" ] && break
   # ignore everything but replacement text
   nohash="${line#'#'}"
   # if stripping leading hash doesn't change line, it doesn't have one
   [ "$nohash" == "$line" ] && continue
   # clear any previous message
   clear_message
   # put up a new xmessage and capture its pid
   xmessage -buttons OK:2 -center "$nohash" &
   xmpid=$!
done