This has use when the order of components in the pool affects draw order
(or has other significance), especially at the subpool level. I plan to
use it for fixing overlapping windows in imui.
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).
The hierarchy leak was particularly troublesome to fix, but now the
hierarchies get updated (and freed) automatically just by removing the
hierarchy reference component from the entity. I suspect there will be
issues with entities that are on multiple hierarchies, but I'll sort
that out later.
I found I needed the subrange start as well as the end, but I liked that
the subpools themselves used only the end of the range, so switching to
just a unint32_t for the value and adding a function to return a tuple
made sense. I had kept the struct because I thought I might want to
store additional information (eg, the entity "owning" the subpool), but
found that I didn't need such information as the systems using subpools
that way would have access to the entity by other means.
Interestingly, the change found a bug in subpool creation: I really
don't know why things worked before, but they work better now :)
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.
While this does require an extra call after registering components, it
allows for multiple component sets (ie, sub-systems) to be registered
before the component pools are created. The base id for the registered
component set is returned so it can be passed to the subsystem as
needed.
This means that the component id used for hierarchy references must be
passed to Hierarchy_New and Hierarchy_Copy, but does all an entity to
have more than one hierarchy, which is useful for canvases (hierarchies
of views) in the 3d world (the canvas root would have a 3d hierarchy
reference and a 2d (view) hierarchy reference).
In the end, it was removal of the old entries that corrupted the parent
indices. Very nicely, most of the fixes involved removing code. Taking
advantage of the ECS to debug the hierarchies was fun, and the resulting
colorized entity names helped no end.
Even 37 objects is a lot, but it's a whole lot better than 180. Most
importantly, it reproduces the problem, which seems to be not all parent
indices getting updated. The child indices seem to be working nice, as
do the reference object indices (ie, the entity components). I suspect
its the parent indices getting corrupted that cause problems on the
second switch of the hud/sbar cvar as the parent indices are used to
find the child indices that need to be updated.
As expected, reparenting a sub-hierarchy such that it (and possibly its
children) move up the arrays fails (this is why sbar needs to first
remove the sub-hierarchy then insert it).
Since test_build_hierarchy2 already tested removal of a sub-hierarchy
(once fixed), it seems test_build_hierarchy3 testing parenting within
the same hierarchy would be a good idea. Reparenting such that
everything moves to later in the arrays works nicely (not very
surprising).
Ugh, things were quite bad, it turns out. It seems a lot of trouble
would have been saved if these tests had worked (however, something is
still not quite right as views are out of place).
This is the bug that sbar found when pulling a sub-hierarchy out of a
larger hierarchy: child indices not getting updated correctly for later
siblings and any niece objects.
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.
Bill Currie