I've tested it and it works as expected.

Maybe I would change "Fit Both" to "Fit Page" in the Preferences, since the matching option in the dropdown menu is Page.

Maybe I would change "Fit Both" to "Fit Page" in the Preferences, since the matching option in the dropdown menu is Page.

Done.

I also added preferences for page layout and scrolling:

It's not great UI design, but again my goal for tonight was just to get something in place and working. (Edit: I added some thoughts on what I think would be better under #1414.)

How does this look? I also included the two settings that were moved from "Tools" in #1920, which I hope will make rebasing easier if we decide to merge this PR first.

Looks good to me!

Feel free to merge it when you think it's complete, then I can rebase #1920

@bmjcode I'm commenting in this PR even though you did not add the following line.

Look at this Raster page layout option. What is this?!? Why is it in the section where you can set a single or double page layout?

Look at this Raster page layout option. What is this?!? Why is it in the section where you can set a single or double page layout?

I put it in the preferences dialog because it's in the corresponding section of the Music menu. What it's for I can't tell you. It was there before I got here.

There's a comment in musicviewers.py saying:

These are from qpageview.view.ViewProperties

In fact the code is here.

And the raster layout is explained here.
I think that preference deserves a tooltip and an explanation in the user manual. I'll test it and open a new PR.