Hi Frank.

>omyForm = CREATEOBJECT("Form")
>omyForm.Dockable = 1 && the form is automatically made visible here!
>?'Top1 ' + trans(omyForm.Top)
>?'Left1 ' + trans(omyForm.Left)
>omyForm.Visible = .f.
>omyForm.Visible = .T. && the form has now moved down from where it was originally
>?'Top2 ' + trans(omyForm.Top)
>?'Left2 ' + trans(omyForm.Left)

Interesting. It turns out Top is moved down by SYSMETRIC(4) (the height of the window frame) + SYSMETRIC(34) (the height of a half-height caption, since dockable forms use that) and Left is moved over by SYSMETRIC(3) (the width of the window frame). Something you may not have noticed is that Height and Width are reduced accordingly. You can see that visually with this code:

omyForm1 = createobject('Form')
omyForm1.HalfHeightCaption = .T.
omyForm1.Visible = .T.

omyForm = CREATEOBJECT("Form")
omyForm.Dockable = 1 && the form is automatically made visible here!
?'Top1 ' + trans(omyForm.Top)
?'Left1 ' + trans(omyForm.Left)
suspend

omyForm.Visible = .f.
omyForm.Visible = .T. && the form has now moved down from where it was originally
?'Top2 ' + trans(omyForm.Top)
?'Left2 ' + trans(omyForm.Left)

suspend

Notice that initially the dockable form is the same height as the non-dockable, but after you type RESUME in the Command window, it exactly fits inside the client area of the non-dockable form.

I think this is by design. Dockable forms have a lot of weird issues. To control visibility, I usually set Dockable to .T. in the Show method so it does become visible until just before the form would have anyway.

Doug