Bug Info:
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I was trying to reduce the height or width of jdailog window,it allows until all the components hide in the container but while compare with native dailog it allows the user to reduce the height or width at some extant and its not allowing the user to hide the dialog container components.

Please check the attached images for compare.

Steps to Reproduce:
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1. Open any dialog demo apps with GTK Look And Feel.
2. Place the cursor on top of the window and the cursor shape changes to allow the resize.
3. Reduce the dailog screen height.

It allows the user until the top window title bar reaches the bottom and it hides the dailog container.But while compare with native it has some minimum and maximum bounds.