Add helpers to enable stable and controllable collapsed state in hierarchical lists

[abey79]

What

This PR introduces a set of helper objects to assist in producing predictable (and thus stable) egui::Id for various objects of our data model (container, space view, data result, etc.). Since the collapsed state is in general not shared across different UI area, this PR proposes a scoping mechanism (implemented with the type system), so the id for a given item is different depending on, e.g., its appearance in the blueprint tree or the streams tree.

This improves the collapsed state in hierarchical lists in two ways:

• The collapsed state is now preserved when objects move in the hierarchy (e.g. a space view is moved from a container to another). Fixes Improve how collapsed state is saved for space views, containers, and DataResults in the Blueprint Tree UI #5208
• It is now possible to "remotely" change the collapsed state of a given item, in a given scope.

⚠️⚠️ Demo "Expend all/Collapse all" buttons are included in the container selection panel, to be reverted before merging.

stable_collapse_id.mp4

Blocked by:

• Do not duplicate the space origin subtree in the blueprint tree UI #5371

To address in follow-up PRs:

• fine-tune the DataResult representation such as to ensure sufficient specificity in case the DataResult appears multiple times in the space view blueprint sub-tree / cc @Wumpf
• add "collapse all"/"expand all" context menu actions
• improve "double-click focus" to uncollapse the focused items

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[emilk]

Nice! Looking forward to the "double-click to focus and expand everywhere" feature :)

[emilk]

It would be kind of nice to have in the context menu 🤔

Especially if it was just one button, showing "expand all" unless it was already all expanded, in which case it would show "collapse all" instead.

[abey79]

Yes! ...but in a follow up PR. This is blocked on sorting out the DataResult story.

[Wumpf]

double-click to focus and expand everywhere

you keep saying double-click but I thought we said it would be single-click? :). (Relatively easy to change nuance ofc, albeit the way 'focus' and 'selection' works maybe not entirely trivial)

[abey79]

double-click to focus and expand everywhere

you keep saying double-click but I thought we said it would be single-click? :). (Relatively easy to change nuance ofc, albeit the way 'focus' and 'selection' works maybe not entirely trivial)

IIRC, single click would only (sister-)select without messing too much with the UI, and only double-click would "flash" the entire UI into showing the thing of interest.

And yeah, right this minute I'm interested in the infrastructure, so we are unencumbered when iterating on the actual UX.