Provide opportunity to forbid resize window.
Can you give an example of a use case where fixed size windows are required? Note that some platform always allow window resizing, notably mobiles and certain Linux window managers.
Hm, I'm not sure when it could be required, it's personal preference for dialogs.
P.S. I am Windows-only user and didn't know about such limitations in other platforms. In this case how about resize limitations? I mean setting minimum (or maximum) possible size?
Resize ranges are not possible to enforce in general either.
The feature may still be a good addition for platforms that can support it, and that's why I ask for the use-cases where resize limitations are important.