node categories

[kamirr]

• Add CategoryTrait that gives a name to a category of nodes. Provide implementations for String, &str and ().
• Add NodeTemplateTrait::node_finder_categories to list categories to which the template belongs, defaults to an empty Vec.
• Node finder now displays at the top a collapsible header for each category and corresponding nodes inside of them. Nodes without a category are displayed below, so the behavior of programs that don't adapt to use categories remains the same. The collapsible headers behave as follows:
  • For empty query, all categories are collapsed
  • Otherwise:
    1. Categories that contain no matching nodes are ommited.
    2. Matching categories are now opened by default -- it's assumed that filtered results are more manageable and can now be unwrapped.
    3. The user can normally un/collapse each category, but if the query is changed, the default is applied.
• Update the example to use this feature.

This change will break all existing programs and the simplest fix to that is adding type CategoryType = (); in the implementation of NodeTemplateTrait. Default associated types are not supported, so this can't be avoided with this design.

[kamirr]

Demo of the adapted example app: egui_ex.webm