I am creating desktop app with master/details view situation.
In a predefined ratio and size it looks fine.
When I resize window to full screen it looks something like this:
What would be a good solution for full screen?
You have a number of options...
Also, since full-screen landscape forms are the norm for tablets, move your submit and cancel buttons up and to the right, leaving the bottom half of the screen free for the on screen keyboard.
Seems like that the only thing you can do here is expand the width of the text input fields to 100% and put the buttons in the lower right corner.
You simply don't have enough material to make a full screen look good.
Or just disable full screen on that view.