What problem does this solve or what need does it fill?

If I want to use this library in my project I need to build and maintain a tree of layout nodes even when I have
some tree already.

What solution would you like?

I propose introducing a trait, called LayoutTree with methods for traversing & accessing the styles. Something like this:

What alternative(s) have you considered?

morphorm is already using similar abstraction, just in a little different flavor. https://github.com/vizia/morphorm/blob/main/src/hierarchy.rs

Additional context

I think there is also another option, in a sense of visitor pattern, so instead of implementing some Tree trait, one could implement TreeVisitor which could look like this:

pub trait LayoutVisitor {
  fn open_node(&mut self, style: &LayoutStyle, dirty_flags: Xxx) -> bool;

  fn close_node(&mut self, result: &mut LayoutResult);

  fn visit_text(&mut self, paragraph: &dyn Paragraph, result: &mut LayoutResult);
}

This way we wouldn't need any Tree::NodeRef because the client is rather supposed to implement internal iteration for this library, including writing the results which means we don't need any id/ref and data can be stored anywhere/anyhow.

BTW: original discussion on reddit https://www.reddit.com/r/rust/comments/v9en4v/comment/ic6pfx9/?utm_source=share&utm_medium=web2x&context=3