This allows components to display themselves in the UI. Because the
component meta-data is copied into the registry, the function pointer
can be updated by systems (eg, the renderers) to display system-specific
interpretations of the component.
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.
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.
There's now a main ecs.h file that includes the sub-system headers,
removing the need to explicitly include several header files, but the
sub-systems are a less cluttered.
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).
While simple component pools can be cleared simply by zeroing their
counts, ones that have a delete function need that function to be called
for all the components in the pool otherwise leaks can happen.
It should have always been here, but when I first created the hierarchy
and transform objects, I didn't know where things would go. Having two
chunks of code for setting an entity's parent was too already too much,
and I expect to have other hierarchy types. Doesn't fix the issues
encountered with sbar, of course.
As the bookkeeping data is spread between three arrays, sorting a
component pool is not trivial and thus not something to duplicate around
the codebase.
It doesn't check that the entity itself is valid, but it does at least
check that the index fetched from the sparse array is valid. Fixes a
segfault when a valid entity never had the component.
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.
