This  patch is inspired by Jonathan Atkin's imwheel2.patch,
but (as opposed to imwheel2)  allows  to  write  a backward
compatible, and avoid  recompiling  all existing  GPM-based
applications. The changes look really awkward, but that was
a mere patch to the existing package.

This patch adds wheel support to serial and PS/2 models of 
Microsoft Intellimouse, A4-tech dual-wheel (4D) mouse and
clones. Use the following command line options:

   gpm  -t ms3       # Serial Intellimouse
   gpm  -t imps2     # PS/2   Intellimouse
   gpm  -t a4d       # Serial A4-tech 4D
   gpm  -t a4dps2    # PS/2   A4-tech 4D

-----------------------------------------------------------

Here is the short description of changes. For a detailed
description refer to gpm.info after applying the patch:

- Stucture Gpm_EventExt replaced Gpm_Event structure.
  It has new appended members:
    w, dw   - wheel1 displacement after previous reading, and
              current wheel position (initially set to 0)		
    w2, dw2 - same for wheel 2
    pad     - reserve for future extensions

- Functions Gpm_GetEventExt, Gpm_GetSnapshotExt are similar
  to Gpm_GetEvent and Gpm_GetSnaphot, but take Gpm_GetEventExt
  as a parameter. Gpm_EventExt is also passed as a parameter
  to Gpm_EventExt, however the old code should work: it will
  just give warnings during compilation. Check presence of
  GPM_EVENT_EXT to find if GpmEventExt is available:

  #ifndef GPM_EVENT_EXT
	# define Gpm_EventExt Gpm_Event
	# define Gpm_GetEventExt Gpm_GetEvent
	# define Gpm_GetSnapshotExt Gpm_GetSnapshot
  #endif

- New event types
		GPM_FWHEEL    wheel 1 forward
		GPM_BWHEEL    wheel 1 backward
		GPM_FWHEEL2   wheel 2 forward (right)
		GPM_BWHEEL2   wheel 2 backward (left)
 
  provide and alternative way of wheel processing similar to
  ZAxis mapping in XFree86.

-------------------------------------------------------------

This patch does not associate wheel motion with a keystroke,
and does not automatically provide text scrolling - 'imwheel'
package by Jonathan Atkins implements those feature, however it
may be inconsistent with the current modifications.

Michael Glickman <xsadp@yahoo.com>