RFR: 8345188: Support tree-structural pseudo-classes [v10]

[John Hendrikx]

On Thu, 9 Jan 2025 18:53:39 GMT, Michael Strauß <mstrauss at openjdk.org> wrote:

> This outcome is what I would expect, and it puts an upper limit on the number of nodes that you can front-insert one by one into a container (the time complexity grows quadratically, so you'll pretty soon freeze the application).
> 
> Note that back-inserting, or bulk-inserting nodes should have no noticeable performance impact.
> 
> I think our options are the following:
> 
> 1. Discard this feature.
> 2. Accept that this particular way of adding nodes to a container has a prohibitive time complexity for many nodes.
> 3. Do something clever, for example only toggle the pseudo-classes once per pulse. The disadvantage of this approach would be that the pseudo-classes of a node may be wrong after it is added to a container, and would then later fix themselves in the next pulse.
> 4. Do something even more clever, for example only set the pseudo-classes when someone is actually listening or retrieving their value.

It may be possible to have these simply be synthetic (including first/only/last child).  If the index of a child is known, and the size of its container, these can be trivially be computed on demand instead of fully materialized and made part of a list.  I couldn't find how browsers generally do this, but I suspect it will be highly optimized.

-------------

PR Comment: https://git.openjdk.org/jfx/pull/1652#issuecomment-2581289531