Yes indeed, this also applies to the other default-font properties. When resolved at run-time, they resolve against the Window of the preview itself, not the Window in the user's Slint code :-(

I'm not sure how to solve that best yet...

We could change the signatures of say fn layout_info(..., window_adapter: &Rc<dyn WindowAdapter>) to something like fn layout_info(..., window_context: &WindowContext) and let WindowContext be a struct with a ref to the window adapter as well as the Pin<&WindowItem>. But besides the difficulty of implementing that, it also wouldn't help for render() itself, when we have to do the same resolution step inside the specific renderer and certainly don't know which WindowItem to pick.

Unless......... perhaps the other way of doing this is - at resolution time - to walk /up/ the item tree, starting at self_rc and then parent() until... we find the Window. That's not great, but it would be correct.

Another slightly related issue is that if one use default-font-size, it will not work when previewing sub components.
Perhaps default-font-size should be a "project" property (#267)? But we would still need to solve the problem on where to get the default font.

I guess the short term solution is indeed to walk up the item tree. But that is a fairly slow operation, we might not want to do that for every rendering of every Text. Adding some kind of WindowContext might not be a bad idea either.

OIivier had a great idea for an optimisation here: We have to walk up the tree, but instead of traversing item by item we can traverse from component to component and just check if item at index 0 is a WindowItem. If it isn't, continue the walk.