Thanks for your reply.
The fonts are working.
But the frame packing problem has surfaced again. I made the following 3 changes you mentioned
1.Minsize for main window
2.top and bottom frame expand=>0 and fill=>x
3.height=>-1 to HList
Doing the above things, frames are getting packed as I want and the 'Display' button on bottomframe is visible at the minimum size of the window. But this works only if I have 2-3 rows of data under the columns.
If I have some 6+ rows , then the gui window is launched with a bigger size and as I contract it to a smaller size the Display button on the bottomframe starts disappearing. Hence the problem still persists. Also the vertical scrollbar on the right hand side has no use if the gui always has to be kept so long to view some 6+ rows. It should stay as small as (380x160) irrespective of the row numbers and one can make use of the scrollbar and yet see all the frames.
One more thing : Clicking on the 'Display file' button opens a scrolled ROText widget. Hence the default font or the selected font if I choose any from the FontDialog later, is getting applied on the ROText widget as well. I think since I am applying RefontTree on the mainwindow ($mw->RefontTree) so it is happening. But can I prevent that anyway ? By that I mean, on the ROText I want the normal Tk font that happens if I do not hard-code any default font or so by RefontTree .
To consolidate, the default font or the selected font from FontDialog will still be applied on $mw but not on the ROText window.