Use compatible text resource format when possible

[timothyqiu]

Use the new format only when saving a resource / scene containing a PackedByteArray with at least 64 elements.

This way, editor settings can be kept, and users can still open most scenes with previous versions of Godot.

This PR is a proof of concept of my suggestion on RocketChat.

Bugsquad edit: Fixes #90846

[KoBeWi]

This makes TileMapLayer save in the old PackedByteArray format, which is wrong.
Tileset does not use PackedByteArray AFAIK.

[timothyqiu]

This makes TileMapLayer save in the old PackedByteArray format, which is wrong.

If you mean the change in TileMapLayer.xml, it's because only resource files are possible to use the new format. In this case, serializing XML still uses the old format indeed.

[KoBeWi]

No I mean I tested with a TileMapLayer in a scene. The whole format change was because of TileMapLayer.

[timothyqiu]

Ah, sorry I missed the recursion part when in VariantWriter. I'll get rid of the setup for TileSet and push again.

[timothyqiu]

It should work correctly now.

prefer_compat_format() is now PackedScene only.

[KoBeWi]

This works correctly and even resolves Resources issue, making my PR irrelevant.

But it's hacky. And also it makes Base64 hard-coded only for TileMapLayer, which means nothing else can benefit from it. I think perfectly scenes/resources should always save under new format if they contain PackedByteArray.

[timothyqiu]

It turns out ResourceFormatSaverTextInstance::_find_resources() goes through every value to be stored. It's a good place to check whether PackedByteArray is used.

Now the resource saver will use the new format if there's a PackedByteArray with at least 64 elements. The hard-coded TileMapLayer check is removed.

The downside is that the format version may change depending on what's inside the resource / scene. Maybe the array size limit is an overthinking, a non-empty check is enough.

[KoBeWi]

Yeah the size check is unecessary. This also means that we have to keep the old PackedByteArray serialization code.
PackedByteArrays are uncommon in scenes/resources and if they exist, they are usually longer. I checked with TileMapLayer and the size is exceeded with just 6 tiles, so it's pointless.

[timothyqiu]

The main reason I added the size check is for potential custom nodes / resources that export PackedByteArray variables.

If the array only contains a few elements, using Base64 won't save much space and is not human readable. Seems not worth breaking compat for.

[KoBeWi]

It's still somewhat hacky, but at least it's no longer hard-coded to one class. It's a nice solution.

[akien-mga]

That approach looks fine to me overall.

I discussed it with @reduz, and we agreed to merge this for now to address the immediate issue, and then:

• Backport support for parsing the new base64 PackedByteArray to 4.1.5 and 4.2.3 (but not saving - so keeping version format 3 there, but being able to parse version 4).
• Eventually consider reverting this compat handling once the currently supported stable versions no longer need it.

[akien-mga]

Thanks!