This patch adds a new `BKE_main_ensure_invariants` function. For now it only
ensures node-tree related invariants, but more may be added over time.
The already existing `ED_node_tree_propagate_change` now internally calls
`BKE_main_ensure_invariants`. We can probably remove this indirection at some
point and call the new function directly, but for now it is kept to keep this
patch small.
This is based on a recent discussion in the Core module meeting:
https://devtalk.blender.org/t/2024-12-12-core-meeting/38074
```cpp
/**
* Makes sure that invariants in original DNA data are maintained after changes.
*
* This function has to be idempotent, i.e. after calling it once, additional calls should not
* modify DNA data further. If it would, it would imply that this function does more than
* maintaining invariants.
*
* This has to be called after any kind of change to original DNA data that may be involved in some
* of the maintained invariants. It's possible to do multiple changes in a row and then fixing all
* invariants with a single call in the end. Obviously, the invariants are not maintained in the
* meantime then and functions relying on them might not work.
*
* If nothing is changed, this function does nothing and it should not be slower than checking a
* flag on every data-block in the given bmain.
*
* Sometimes, it is known that only a single or very few data-blocks have been changed (e.g. when a
* node has been inserted in a node tree). Passing in #modified_ids can speed up the function
* because it may avoid the need to iterate over all data-blocks to find modified data-blocks.
*
* Examples of maintained invariants:
* - Group nodes need to have the correct sockets based on the referenced node group.
* - The geometry nodes modifier needs to have the correct inputs based on the referenced group.
*/
void BKE_main_ensure_invariants(Main &bmain,
std::optional<blender::Span<ID *>> modified_ids = std::nullopt);
```
This also adds `windowmanager` as a dependency of `blenkernel` to be able to
send notifiers.
Pull Request: https://projects.blender.org/blender/blender/pulls/132023
1fae5fd8f6