ini:
MouseControl=Управление режимом отображения графиков с помощью мыши|4|0|TrueXY,TrueX,TrueY,False

code:
procedure THIPlotter._onMouseWheel;
var h:real;
i:real;
begin
inherited;
if _prop_MouseControl=3 then exit;
i := (integer(Mouse.Shift) / $1000)*0.0001;
if ((_prop_MouseControl=0) or (_prop_MouseControl=2)) then
begin
h := _prop_MaxH - (_prop_MaxH - _prop_MinH) * (FStartPos.y - _prop_TopMargin)/(Control.Height - _prop_TopMargin - _prop_BottomMargin);
_prop_MaxH := _prop_MaxH - i*(_prop_MaxH - h);
_prop_MinH := _prop_MinH - i*(_prop_MinH - h);
end;
if ((_prop_MouseControl=0) or (_prop_MouseControl=1)) then
begin
h := _prop_MinW + (_prop_MaxW - _prop_MinW) * (FStartPos.x - _prop_LeftMargin)/(Control.Width - _prop_LeftMargin - _prop_RightMargin);
_prop_MaxW := _prop_MaxW - i*(_prop_MaxW - h);
_prop_MinW := _prop_MinW - i*(_prop_MinW - h);
end;
ReDraw;
end;