For a large CHM, resizing the main window may take
considerable time (I counted 10 sec. on a 40megs file
-- the java api 1.4.2). I tracked it down to the
ListCtrl computation of text width. I added code to
perform such computation only when a new file is open
(since that is the only time the index list is
changed). Seems to work fine with any kind of files now.