MDI: QDialog modality locks Application instead parent QMdiSubWindow only

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Hi!
I need to work with QMdiSubWindow example even if another is lock at this time.
My app inheritance structure:

MainWindow
-- QMdiArea
----QMdiSubWindow
--------MyWidget (QWidget)
------------MyDialog (QDialog)

MyDialog shows only when user have to wait. MyDialog is a my own analogue of QProgressDialog.
MyDialog flags: Qt::FramelessWindowHint, Qt::CustomizeWindowHint, Qt::SubWindow, Qt::Tool.

Problems:

1. If i don't set a modality, user has availability to move this subwindow and MyDialog will stay at old position as a result.
2. MyDialog and MyWidget doesn't recieve move event if i move its QMdiSubWindow
3. If i set WindowModality for MyDialog, an application will be locked, not a QMdiSubwindow.

Thanks for any advice.