How to detect current Left and Top of Form when dragging (in Delphi)?

Question

I need to detect the Left and Top value of the Form (in real time) by dragging and displaying the values in Spinedits (Sedtx and Sedty).

I am using the code below, but without success:

 private
   { Private declarations }
   procedure WMNCHitTest(var M: TWMNCHitTest);

Procedure:

procedure TFrmMain.WMNCHitTest(var M: TWMNCHitTest);
begin
 inherited;
    if M.Result = htCaption then
    //Ao arrastar o Form atualiza os SpinEdits
    SEdtX.Value := FrmMain.Left;
    SEdtY.Value := FrmMain.Top;
end;

What should I change?

Answer 1

The problem is in the method declaration. It expects a operating system message to fire it. Failed to declare which message he is waiting for, the correct statement would be:

procedure WMNCHitTest(var Message: TWMNCHitTest); message WM_NCHITTEST;

Updating:

The most appropriate message for this purpose is WM_WINDOWPOSCHANGING, this captures in real time the motion of the screen.

procedure WMPosChanging(var Msg: TWmWindowPosChanging); message WM_WINDOWPOSCHANGING;