Carbon has

LM_MOUSEWHEEL:

       begin
         y := PLMMouseEvent(@AMessage)^.Y;
         x := PLMMouseEvent(@AMessage)^.X;
       end;

but need one more: LM_MOUSEWHEEL_HORZ, maybe. Mac trackpad can scroll view with 2 fingers: vert scroll already does lm_mousewheel, and horz scroll....? Does nothing. It does 1/n part of mousewheel, and so my app scrolls vertical. App must scroll horizontal only. Can we have new LM?

I wanted this change:
- Carbon WS can read horz mouse wheel. it sends e.g. LM_WHEELSCROLL_HORZ
- LCL generates as usual OnMouseWheel (....Up/Down), but if it is horiz wheel move, then
it adds flag ssScrollHorz to Shift parameter.
- app can detect horiz wheel move, by ssScrollHorz

No need to add new events OnMouseWheelHorz, only add item to Shift. What do you think.
Alexey