Maybe the view_wants_decorations() check should be moved too.

This prevents setting the output before map, intended?
From memory that is required for scale notifications to work before map but I am not sure right now. @ahesford might be able to confirm.

Edit:
It was actually introduced via ed19bc4

This prevents setting the output before map, intended?

There is still this code in xdg_toplevel_new():

/*
 * Pick an output for the surface as soon as its created, so that the
 * client can be notified about any fractional scale before it is given
 * the chance to configure itself (and possibly pick its dimensions).
 */
view_set_output(view, output_nearest_to_cursor(server));
if (view->output) {
	wlr_fractional_scale_v1_notify_scale(xdg_surface->surface,
		view->output->wlr_output->scale);
}

Does that address the concern?

I think the assignment of an output in xdg_toplevel_new, which was added to make sure foot sets its initial size based on a correct output scale, is probably sufficient even in cases when a view is initially maximized.

In that case I think we can remove the view_set_output() calls in the fullscreen and maximized handlers as output will always be set via xdg_toplevel_new().

I agree this later assignments of view->output are probably a bit paranoid. I think it's a bit out of scope for this PR to remove them so I think I'll leave them as-is for now.

Alright, PR LGTM, not tested. Feel free to merge if you are satisfied with it.