Firemonkey TVertScrollBox mouse position - delphi

Question

I have form (Height = 500) and TVertScrollBox on it (align set to TAlignLayout.Client and range is 5000px). I wrote simple method, which show position of mouse when I click on scroll box.
procedure TformMain.VertScrollBox1MouseDown(Sender: TObject;
Button: TMouseButton; Shift: TShiftState; X, Y: Single);
begin
ShowMessage(FloatToStr(X) + ' ' + FloatToStr(Y));
end;
When the scroll bar is on top and I click on top of the scroll box, Y in message is 0. That's right. But when I scroll down to the half and click on top of the scroll box, Y in message is 0, too (not 2500). How can I get the position relative to scroll box?
This is my FMX code for TForm and TVertScrollBox:
object formMain: TformMain
Left = 0
Top = 0
BorderIcons = [biSystemMenu, biMinimize]
BorderStyle = Single
Caption = 'Gear Studio 1.0'
ClientHeight = 600
ClientWidth = 450
Position = DesktopCenter
StyleBook = StyleBookPanel
FormFactor.Width = 320
FormFactor.Height = 480
FormFactor.Devices = [Desktop]
OnCreate = FormCreate
OnCloseQuery = FormCloseQuery
DesignerMasterStyle = 0
object VertScrollBox1: TVertScrollBox
Align = Client
Size.Width = 450.000000000000000000
Size.Height = 576.000000000000000000
Size.PlatformDefault = False
StyleLookup = 'VertScrollBox1Style1'
TabOrder = 1
OnMouseDown = VertScrollBox1MouseDown
Viewport.Width = 450.000000000000000000
Viewport.Height = 576.000000000000000000
end
...
...
end
That's how I am adding panels:
SetLength(MyItems, i+1);
MyItems[i] := TItem.Create(i);
with MyItems[i] do begin
...
end;
constructor TItem.Create(number: integer);
var
ThisItem: TItem;
begin
inherited Create(nil);
ThisItem := Self;
with ThisItem do begin
if number = -1 then begin
... //not important
end;
end else if number > 0 then begin
Width := 370;
Height := 35;
...
end;
Position.X := 10;
Parent := formMain.VertScrollBox1;
PopupMenu := formMain.PopupMenu1;
OnDblClick := DblClick;
OnMouseEnter := MouseEnter;
OnMouseLeave := MouseLeave;
end;
end;
MyItems is dynamical array of TItem (it is normal TPanel with added some properties).

Answer 1

You need to add VertScrollBox1.ViewportPosition.Y property to get the absolute coordinate.
ShowMessage(FloatToStr(X) + ' ' + FloatToStr(VertScrollBox1.ViewportPosition.Y+Y));
shows correct result.