Blender Git Commit Log

UI: Allow registering File Browser as child of other child windows

E.g. when opening the File Browser from the Preferences window, it would
be the child of the main window the Preferences belong to. Now it can be
a child of the Preferences window itself.
The File Browser always stays on top of its parent window. Which avoids
some issues with OS window management, see T76418 and T72693.
Also removes a now unnecessary workaround to move the child window back
to the front after closing the file browser (opening the file browser
would move the main window and the file browser to the front).

Fixes T76418, T72693.