Curses window structure question

[Brett Galloway]

I am interested in using curses for a limited window-management program.
In particular, I would like to maintain a scroll buffer which the user
could move back to to look at output which had scrolled off the top of the
screen.  In order to do this efficiently, I would like to allocate two
curses windows - one which always overlays the bottom (page) of the
scroll buffer; and one which overlays the current display location of the
scroll buffer.  I would like to munge the line pointers in the two windows
to point into my scroll buffer instead, so that I can use the curses
functions waddstr() and waddch() to add characters to the bottom window (normal
output), which should thereby update the scroll buffer as well.  I would like
to write my own scroll routine, to scroll the bottom window appropriately
through the scroll buffer.  The user could then move the other window to look
at different locations in the scroll buffer.

The problem is that the curses WINDOW structure has two fields,

	short	*_firstch,*_lastch;

for which I have no documentation; I am afraid that if I munge the _y field
(the line pointer array field) to point into my scroll buffer that these
two fields will be inconsistent or wrong; without further information, I
just don't know what can bite me.

Therefore, any information/advice would be appreciated.  I am working on
a VAX 11/750, under 4.2BSD.

Thanks in advance.

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Brett Galloway
{pesnta,twg,ios,qubix,turtlevax,tymix,vecpyr,certes,isi}!wjvax!brett