How to direct the mouse wheel input to control under cursor instead of focused?

Question

I use a number of scrolling controls: TTreeViews, TListViews, DevExpress cxGrids and cxTreeLists, etc. When the mouse wheel is spun, the control with focus receives the input no matter what control the mouse cursor is over.

How do you direct the mouse wheel input to whatever control the mouse cursor is over? The Delphi IDE works very nicely in this regard.

Answer 1

Try overriding your form's MouseWheelHandler method like this (I have not tested this thoroughly):

procedure TMyForm.MouseWheelHandler(var Message: TMessage);
var
  Control: TControl;
begin
  Control := ControlAtPos(ScreenToClient(SmallPointToPoint(TWMMouseWheel(Message).Pos)), False, True, True);
  if Assigned(Control) and (Control <> ActiveControl) then
  begin
    Message.Result := Control.Perform(CM_MOUSEWHEEL, Message.WParam, Message.LParam);
    if Message.Result = 0 then
      Control.DefaultHandler(Message);
  end
  else
    inherited MouseWheelHandler(Message);

end;