Yet another GTK3 - SDL2 topic

This question has been asked many times, but could not find a solution.
I would like to use GTK3 to open some modal (configuration) dialogs in a SDL2 app.

After reading

I can get a gtk dialog to open, but when I close it, the window does not go away.

Tried to add

while (gtk_events_pending()) // are there GTK events to handle

but it is not make any difference.

Is this possible at all?
Should one instead use embed SDL into GTK?
Are there any (good) example out there?

I am not looking for a full integration, but simply a way to get (modal) configuration dialogs available.


The code for my gtk dialog is here