Dialogs spawned by FileChooser have extra empty space

[junrrein]

First of all, I'm not sure which component I should file this bug against.

It seems that when using a Flatpaked application that uses GtkFileChooserNative, file dialogs are spawned with some extra space on the right, that disappears when a file gets selected:

This happens in an app I develop, but only when running the Flatpaked version. If I run it straight from the compiled sources, this doesn't happen.

I can also replicate this issue with Firefox, which is strange since I'm not using the Flatpaked version.

Using:

• Fedora 31
• xdg-desktop-portal 1.4.2
• xdg-desktop-portal-gtk 1.4.0
• Firefox 74.0

[junrrein]

Thanks a lot!