No icons in development on Big Sur

[Nick Partridge]

Hi ,

When I run Frescobaldi from source (on Mac/Big Sur I should add), the interface is missing all the icons from both the menus and the toolbars - https://drive.google.com/file/d/1npdkuY2xUFDvYXKYbIXOXspKNGNlhjo_/view?usp=sharing

I don't have this problem when running the built application from the releases page `Frescobaldi-3.1.2-x86_64-10.11.dmg`, so I suspect I might be missing some step or dependency that makes the icons work.

I've done some print-debugging in icons/__init__.py, and it looks like the icons are being found and loaded, just showing up blank.

I'm not using the system python, I'm using python 3.8 installed via Nixpkgs (https://github.com/nkpart/frescobaldi/blob/nkpart/drum-score-operations/shell.nix). All the python packages are coming from pipy, except for qpageview which I pull from GitHub.

Is there anything dependency I need to get the icons to render? Do I need to run something before `python frescobaldi` to get the icons packaged? Or, is there another way I should be building/running the application when developing on Mac?

Any help would be appreciated!

Cheers

 - Nick