Scrolling and inserting/deleting lines

[Bill-Gray]

wsetscrreg( WINDOW *win, int top, int bottom) requires that the cursor be somewhere between top and bottom. I don't see why. I suspect it mattered once upon a time and no longer does. The actual scrolling just scrolls the region between top and bottom (stored in win->_tmarg and win->_bmarg), with no reference to the cursor location. ncurses ignores the cursor location for this function.

On a slightly related matter : wdeleteln() will delete the line under the cursor and move everything from there to the bottom of the scroll region (win->_bmarg) up one line. If the cursor is below the bottom margin of the scroll region, wdeleteln() erases the current line and does nothing else.

winsertln() will insert a blank line at the cursor position and push everything down to the bottom of the window (win->_maxy - 1). I think wdeleteln() is the one in error here (ncurses also seems to think that the deletion/insertion should go right down to the bottom of the window). Basically, the scrolling functions should always look at _bmarg and _tmarg and never at the cursor location. winsertln()/wdeleteln() should always look at the current cursor y value and the bottom of the window, and never at _bmarg or _tmarg. (Well, winsertln() already does this; only wdeleteln() requires tweaking. Fortunately, not much of it.)

I have written a small test program to exercise these functions that may be useful.