[Bug 21660] New: Wacom bounding rectangle top coordinates ignored

http://bugs.winehq.org/show_bug.cgi?id=21660

Summary: Wacom bounding rectangle top coordinates ignored
           Product: Wine
           Version: 1.1.38
          Platform: x86
        OS/Version: Linux
            Status: UNCONFIRMED
          Severity: minor
          Priority: P2
         Component: wintab32
        AssignedTo: [e-mail]
        ReportedBy: [e-mail]

Created an attachment (id=26156)
 --> (http://bugs.winehq.org/attachment.cgi?id=26156)
DUMPCONTEXT for TopX/Y = 10000 and BottomX/Y defaults

When setting TopX/Y and BottomX/Y with xsetwacom the resulting bounding box
gets ignored. This makes the cursor draw in a different location than where it
is displayed.

Looking at the tablet context I see that TopXY and BottomXY get mapped directly
to InOrgX/Y and InExtX/Y, while OutOrgX/Y is always 0 and OutExtX = InExtX ,
OutExtY = -InExtY .
I tested this with artrage studio pro, and Gimp for windows, with an intuos3. I
couldn't get gimp to use the tablet properly, but the context was exactly the
same as in artrage.

The function ScaleForContext in dlls/wintab32/context.c seems to use InExt and
OutExt as extents (right - left coordinate) while they're being set as absolute
coordinates. Also the OutExt for the Y axis is always negative, but negative Y
values do not work at all.

Replacing ScaleForContext with a simple linear mapping from [InOrg , InExt] to
[OutOrg, OutExt], returning an absolute value of the result to cope with the
negative Y axis, and removing Y axis flipping later on the same file, seems to
fix the issue: 
ScaleForContext : 
replace with :
    LONG Out;
    Out = (LONG)(OutOrg + ( ( In - InOrg) * (float)(OutExt - OutOrg)) / (InExt
- InOrg));
    return abs(Out)

AddPacketToContextQueue:
remove : 
            /* flip the Y axis */
            if (ptr->context.lcOutExtY > 0)
                packet->pkY = ptr->context.lcOutExtY - packet->pkY;
            else if (ptr->context.lcOutExtY < 0)
                packet->pkY = abs(ptr->context.lcOutExtY + packet->pkY);

This even works correctly for negative TopX/Y values and out of bounds BottomXY
values, which can map the entire tablet area to a portion of the screen.

I have a few questions however. Where do OutOrg and OutExt get set, and why is
OutExtY always negative ? And most importantly, are the above changes correct?