When node tree `A` is not in the tree, `remove_child(B)` will not
automatically clean up the owners of `B` and `B`'s child nodes.
This is convenient for implementing operations like `replace_by()`,
but may have hidden dangers when manipulating the rest of the tree
`A`.
This commit makes it safe to manipulate the rest of `A` after freeing
`B`.
The associated `ViewportTexture`s will update the `viewport_path`
in time when the `Viewport`'s nodepath is changed (caused by renaming
the node names or moving in the SceneTree dock).
If the target `Viewport` is changed by resetting the `viewport_path`,
the `ViewportTexture`s will be re-setup and emit `changed` signal in
time.
* Node processing works on the concept of process groups.
* A node group can be inherited, run on main thread, or a sub-thread.
* Groups can be ordered.
* Process priority is now present for physics.
This is the first steps towards implementing https://github.com/godotengine/godot-proposals/issues/6424.
No threading or thread guards exist yet in most of the scene code other than Node. That will have to be added later.
* Adding and removing child nodes is now constant time, speed up should be huge.
* Searching for node paths as in ("path/to/node") should be far faster too.
This changes the children management and makes it a hashmap, optimizing most StringName based operations.
Most operations should be severe speed up without breaking compatibility.
This should fix many issues regarding to node access performance, and may also speed up editor start/end, but benchmarks are needed. So if you want to test, please make some benchmarks!
Further performance improvements will be done in the future by removing NOTIFICATION_MOVED_IN_PARENT and replacing by something less laborious.
With change 104392e the code to update node indices on removal was erronously removed.
The out of date indices would cause crashes while selecting nodes in a graph editor (e.g. animation tree) and selected nodes are oftern pushed to beginning or end of the child list for the parent.
* This notification makes node children management very inefficient.
* Replaced by a NOTIFICATION_CHILDREN_CHANGED (and children_changed signal).
* Changed Canvas code (and similar) to use the above signal, to perform more efficiently.
This PR breaks compatibility (although this notification was very rarely used, even within the engine), but provides an alternate way to do the same.
It is required for the changes in #75627 to be entirely effective.
