Unity 6.5 support

[lknlknim]

Feature

With Unity 6000.5.0f1 or 6000.5.1f1 and Cesium For Unity 1.23.3 we have 7 compile errors. All of them are related to TreeView / TreeViewItem / TreeViewState

Library\PackageCache\com.cesium.unity@3ba3c11a7bfa\Source\Editor\IonAssetsTreeView.cs(99,46): error CS0619: 'TreeView' is obsolete: 'TreeView is now deprecated. You can likely now use TreeView<int> instead and not think more about it. But if you were using that identifier to store InstanceID data, you should instead opt to upgrade your TreeViews to use TreeView<InstanceID> to get the proper typing.'

Library\PackageCache\com.cesium.unity@3ba3c11a7bfa\Source\Editor\IonAssetsTreeView.cs(138,28): error CS0619: 'TreeViewItem' is obsolete: 'TreeViewItem is now deprecated. You can likely now use TreeViewItem<int> instead and not think more about it. But if you were using that identifier to store InstanceID data, you should instead opt to upgrade your TreeViews to use TreeViewItem<InstanceID> to get the proper typing.'

Library\PackageCache\com.cesium.unity@3ba3c11a7bfa\Source\Editor\IonAssetsTreeView.cs(147,58): error CS0619: 'TreeViewItem' is obsolete: 'TreeViewItem is now deprecated. You can likely now use TreeViewItem<int> instead and not think more about it. But if you were using that identifier to store InstanceID data, you should instead opt to upgrade your TreeViews to use TreeViewItem<InstanceID> to get the proper typing.'

Library\PackageCache\com.cesium.unity@3ba3c11a7bfa\Source\Editor\IonAssetsTreeView.cs(147,34): error CS0619: 'TreeViewItem' is obsolete: 'TreeViewItem is now deprecated. You can likely now use TreeViewItem<int> instead and not think more about it. But if you were using that identifier to store InstanceID data, you should instead opt to upgrade your TreeViews to use TreeViewItem<InstanceID> to get the proper typing.'

Library\PackageCache\com.cesium.unity@3ba3c11a7bfa\Source\Editor\IonAssetsTreeView.cs(205,48): error CS0619: 'TreeViewItem' is obsolete: 'TreeViewItem is now deprecated. You can likely now use TreeViewItem<int> instead and not think more about it. But if you were using that identifier to store InstanceID data, you should instead opt to upgrade your TreeViews to use TreeViewItem<InstanceID> to get the proper typing.'

Library\PackageCache\com.cesium.unity@3ba3c11a7bfa\Source\Editor\CesiumIonAssetsWindow.cs(32,17): error CS0619: 'TreeViewState' is obsolete: 'TreeViewState is now deprecated. You can likely now use TreeViewState<int> instead and not think more about it. But if you were using that identifier to store InstanceID data, you should instead opt to upgrade your TreeViews to use TreeViewState<InstanceID> to get the proper typing.'

Library\PackageCache\com.cesium.unity@3ba3c11a7bfa\Source\Editor\IonAssetsTreeView.cs(103,34): error CS0619: 'TreeViewState' is obsolete: 'TreeViewState is now deprecated. You can likely now use TreeViewState<int> instead and not think more about it. But if you were using that identifier to store InstanceID data, you should instead opt to upgrade your TreeViews to use TreeViewState<InstanceID> to get the proper typing.'

[timoore]

I took a look at this in the course of testing for #677 . While the errors mentioned in the issue are pretty easy to solve by following the instructions in the error messages, a deeper problem for 6.5 is that instance Ids are firmly deprecated in favor of EntityId. This should not be hard to resolve if we can compare and hash the opaque EntityId, but what's the best way to do that :

• use C# methods like GetHashCode(). What would need to happen to be able to do that in C++?
• Do something gross in C++ with reinterpret_cast<>

@kring, @david-lively ?

[kring]

Calling GetHashCode from C++ is easy - just add it to ConfigureReinterop like anything else.

But if the new EntityID APIs are only available in 6.4+, and the old InstanceID APIs aren't available in 6.5+, then we have a problem, because we only build one version of the Native code that is meant to work across all Unity versions.

To solve this, I suggest we move the EntityID / InstanceID distinction out of our native code completely. Everywhere we currently call GetInstanceID, for example, we should now call a new C# method that we provide. The new method would look something like this (not tested):

public static ulong GetInstanceOrEntityID(UnityEngine.Object o)
{
#if UNITY_6000_4_OR_NEWER
    return EntityId.ToULong(o.GetEntityId());
#else
    return (ulong)o.GetInstanceId();
#endif
}

We may need other similar functions. And add this to ConfigureReinterop so it can be called from C++, of course.

Because the C# code is compiled for each Unity version (unlike the native code), this will allow our plugin to work across Unity versions without needing to add a separate native build for different versions.

[brendan-duncan]

I had looked at this a couple months ago and made a branch to get things building, but I might not have time to make a proper PR.
main...brendan-duncan:cesium-unity:entityid

[brendan-duncan]

Your idea of moving the ID to a single point to minimize branch checks is a good idea.
Don't ask me why they made this change. Probably something to do with getting ready for CoreCLR, it's not an area I know anything about.