void PrefabUtility::updateFromPrefab(const HSceneObject& so)
{
HSceneObject topLevelObject = so;
while (topLevelObject != nullptr)
{
if (!topLevelObject->mPrefabLinkUUID.empty())
break;
if (topLevelObject->mParent != nullptr)
topLevelObject = topLevelObject->mParent;
else
topLevelObject = nullptr;
}
Stack<HSceneObject> todo;
todo.push(topLevelObject);
// Find any prefab instances
Vector<HSceneObject> prefabInstanceRoots;
while (!todo.empty())
{
HSceneObject current = todo.top();
todo.pop();
if (!current->mPrefabLinkUUID.empty())
prefabInstanceRoots.push_back(current);
UINT32 childCount = current->getNumChildren();
for (UINT32 i = 0; i < childCount; i++)
{
HSceneObject child = current->getChild(i);
todo.push(child);
}
}
// Stores data about the new prefab instance and its original parent and link id
// (as those aren't stored in the prefab diff)
struct RestoredPrefabInstance
{
HSceneObject newInstance;
HSceneObject originalParent;
SPtr<PrefabDiff> diff;
UINT32 originalLinkId;
};
Vector<RestoredPrefabInstance> newPrefabInstanceData;
// For each prefab instance load its reference prefab from the disk and check if it changed. If it has changed
// instantiate the prefab and destroy the current instance. Then apply instance specific changes stored in a
// prefab diff, if any, as well as restore the original parent and link id (link id of the root prefab instance
// belongs to the parent prefab if any). Finally fix any handles pointing to the old objects so that they now point
// to the newly instantiated objects. To the outside world it should be transparent that we just destroyed and then
// re-created from scratch the entire hierarchy.
// Need to do this bottom up to ensure I don't destroy the parents before children
for (auto iter = prefabInstanceRoots.rbegin(); iter != prefabInstanceRoots.rend(); ++iter)
{
HSceneObject current = *iter;
HPrefab prefabLink = static_resource_cast<Prefab>(gResources().loadFromUUID(current->mPrefabLinkUUID, false, false));
if (prefabLink.isLoaded(false) && prefabLink->getHash() != current->mPrefabHash)
{
// Save IDs, destroy original, create new, restore IDs
SceneObjectProxy soProxy;
UnorderedMap<UINT32, GameObjectInstanceDataPtr> linkedInstanceData;
recordInstanceData(current, soProxy, linkedInstanceData);
HSceneObject parent = current->getParent();
SPtr<PrefabDiff> prefabDiff = current->mPrefabDiff;
current->destroy(true);
HSceneObject newInstance = prefabLink->_clone();
// When restoring instance IDs it is important to make all the new handles point to the old GameObjectInstanceData.
// This is because old handles will have different GameObjectHandleData and we have no easy way of accessing it to
// change to which GameObjectInstanceData it points. But the GameObjectManager ensures that all handles deserialized
// at once (i.e. during the ::instantiate() call above) will share GameObjectHandleData so we can simply replace
// to what they point to, affecting all of the handles to that object. (In another words, we can modify the
// new handles at this point, but old ones must keep referencing what they already were.)
restoreLinkedInstanceData(newInstance, soProxy, linkedInstanceData);
restoreUnlinkedInstanceData(newInstance, soProxy);
newPrefabInstanceData.push_back({ newInstance, parent, prefabDiff, newInstance->getLinkId() });
}
}
// Once everything is instantiated, apply diffs, restore old parents & link IDs for root.
for (auto& entry : newPrefabInstanceData)
{
// Diffs must be applied after everything is instantiated and instance data restored since it may contain
// game object handles within or external to its prefab instance.
if (entry.diff != nullptr)
entry.diff->apply(entry.newInstance);
entry.newInstance->mPrefabDiff = entry.diff;
entry.newInstance->setParent(entry.originalParent, false);
entry.newInstance->mLinkId = entry.originalLinkId;
}
gResources().unloadAllUnused();
}
