[screen-devel] Hacking in different alt-screen support

[cwillu]

I'm experimenting with implementing a different approach to
alt-screen, similar to the effect of termcapinfo ti@:te@, except when
using an app which actually requests alt mode.

The specific goal I have is to have a working mouse-wheel in both
shells and pagers in terminals which change mouse-wheel behavior
depending on the terminal mode.  Currently, scrolling in a shell pages
through the history list or similar, while scrolling in a pager or
editor generally works properly.  Setting ti@:te@ gets usable behavior
out of shells, but loses the ability to scroll in less, vim, and so
forth.

The idea is to restore somewhat sane mouse-wheel scrolling by setting
screen to not use alternate mode until a running app actually requests
it.

Attached is the (not working) patch I've come up with so far.

AddCStr(...) appears to be modifying a global, which then gets flushed
out to the tty on Flush(), but repeating the calls (D_TI/TE) in
Enter/LeaveAltScreen doesn't seem to do anything (after removing the
D_TI/TE's in the initialization);  I'm not certain if that's because
it's the wrong call, or just the wrong place for the call.  It's
possible that Enter/LeaveAltScreen isn't the right place to put those
calls, although that seems unlikely, as they're called almost directly
from where an app's ti/te would be handled.

--Carey Underwood

different-altscreen-behaviour.patch
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