On Thu, Dec 10, 2015 at 4:42 AM, Neil C Smith <neilcsmith.net@googlemail.com> wrote:

The UI toolkit I use for Praxis LIVE starts off as single window, but allows the user to drag features around inside the main window, or outside into a new window.

Thus duplicating the functions of a window manager both inside and outside your application, and causing cognitive dissonance for the user if the external WM behaves differently from the internal one. It is cool, but I'm not sure it is wise.

Surely that's a feature of most UI toolkits that support MDI, and actually meets both requirements above?

Most UI toolkits do not support MIDI. Most UI toolkits do not allow the user to edit layouts at run-time.