As I had long suspected, building large hierarchies is fiendishly
expensive (at least O(N^2)). However, this is because the hierarchies
are structured such that adding high-level nodes results in a lot of
copying due to the flattened (breadth-first) layout (which does make for
excellent breadth-first performance when working with a hierarchy).
Using tree mode allows adding new nodes to be O(1) (I guess O(N) for the
size of the sub-tree being added, but that's not supported yet) and
costs only an additional 8 bytes per node. Switching from flat mode to
tree mode is very cheap as only the additional tree-related indices need
to be fixed up (they're almost entirely ignored in flat mode). Switching
from tree to flat mode is a little more expensive as the entire tree
needs to be copied, but it seems to be an O(N) (size of the tree).
With this, building the style editor window went from about 25% to about
5% (and most of that is realloc!), with a 1.3% cost for switching from
tree mode to flat mode.
There's still a lot of work to do (supporting removal and tree inserts).
Subpools are for grouping components by some criterion. Any component
that has a rangeid callback will be grouped with other components that
return the same render id. Note that the ordering of components within a
group will be affected by adding a component into a group that comes
before that group (or removing a component).
Component pools can have multiple groups, added and removed dynamically,
but removing a group should (currently) be done only when empty.
The hierarchy-specific tests from the transform tests have been moved
into the ecs tests and the transform tests renamed appropriately. As
part of the process, hierarchies can now have a null type (ie, no
additional components maintained by the hierarchy). This should make
sorting out the issues highlighted by sbar a bit easier.
While the libraries are probably getting a little out of hand, the
separation into its own directory is probably a good thing as an ECS
should not be tied to scenes. This should make the ECS more generally
useful.
