Add GDExtension compatibility methods

[RedworkDE]

Requires #76446. Split into many commit to make it possible to cherry pick only the relevant bits (assuming that #76446 gets backported). I will add a commit with compat bindings for #75779, if that becomes possible. looks like that's not happening (for now)

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Compared to 4.0.2 this leaved one reported issue:

Validate extension JSON: API was removed: classes/AnimationTrackEditPlugin

Which was completely useless and intentionally removed.

Compared to 4.0.1 a whole bunch of additional issues appear, that are all the hash changes that can't have compat methods atm:

Validate extension JSON: Error: Hash mismatch for 'classes/AnimatedSprite2D/methods/play'. This means that the function has changed and no compatibility function was provided.
Validate extension JSON: Error: Hash mismatch for 'classes/AnimatedSprite3D/methods/play'. This means that the function has changed and no compatibility function was provided.
Validate extension JSON: Error: Hash mismatch for 'classes/Animation/methods/compress'. This means that the function has changed and no compatibility function was provided.
Validate extension JSON: Error: Hash mismatch for 'classes/AnimationPlayer/methods/play'. This means that the function has changed and no compatibility function was provided.
Validate extension JSON: Error: Hash mismatch for 'classes/AudioStreamPlayer/methods/play'. This means that the function has changed and no compatibility function was provided.
Validate extension JSON: Error: Hash mismatch for 'classes/AudioStreamPlayer2D/methods/play'. This means that the function has changed and no compatibility function was provided.
Validate extension JSON: Error: Hash mismatch for 'classes/AudioStreamPlayer3D/methods/play'. This means that the function has changed and no compatibility function was provided.
Validate extension JSON: Error: Hash mismatch for 'classes/CanvasItem/methods/draw_set_transform'. This means that the function has changed and no compatibility function was provided.
Validate extension JSON: Error: Hash mismatch for 'classes/Curve2D/methods/sample_baked'. This means that the function has changed and no compatibility function was provided.
Validate extension JSON: Error: Hash mismatch for 'classes/Curve2D/methods/sample_baked_with_rotation'. This means that the function has changed and no compatibility function was provided.
Validate extension JSON: Error: Hash mismatch for 'classes/Curve2D/methods/tessellate_even_length'. This means that the function has changed and no compatibility function was provided.
Validate extension JSON: Error: Hash mismatch for 'classes/Curve3D/methods/sample_baked'. This means that the function has changed and no compatibility function was provided.
Validate extension JSON: Error: Hash mismatch for 'classes/Curve3D/methods/sample_baked_with_rotation'. This means that the function has changed and no compatibility function was provided.
Validate extension JSON: Error: Hash mismatch for 'classes/Curve3D/methods/tessellate_even_length'. This means that the function has changed and no compatibility function was provided.
Validate extension JSON: Error: Hash mismatch for 'classes/DisplayServer/methods/tts_speak'. This means that the function has changed and no compatibility function was provided.
Validate extension JSON: Error: Hash mismatch for 'classes/Font/methods/find_variation'. This means that the function has changed and no compatibility function was provided.
Validate extension JSON: Error: Hash mismatch for 'classes/GridMap/methods/make_baked_meshes'. This means that the function has changed and no compatibility function was provided.
Validate extension JSON: Error: Hash mismatch for 'classes/Image/methods/save_jpg_to_buffer'. This means that the function has changed and no compatibility function was provided.
Validate extension JSON: Error: Hash mismatch for 'classes/Image/methods/save_webp_to_buffer'. This means that the function has changed and no compatibility function was provided.
Validate extension JSON: Error: Hash mismatch for 'classes/Image/methods/bump_map_to_normal_map'. This means that the function has changed and no compatibility function was provided.
Validate extension JSON: Error: Hash mismatch for 'classes/PhysicsBody2D/methods/move_and_collide'. This means that the function has changed and no compatibility function was provided.
Validate extension JSON: Error: Hash mismatch for 'classes/PhysicsBody3D/methods/move_and_collide'. This means that the function has changed and no compatibility function was provided.
Validate extension JSON: Error: Hash mismatch for 'classes/PhysicsBody3D/methods/test_move'. This means that the function has changed and no compatibility function was provided.
Validate extension JSON: Error: Hash mismatch for 'classes/RandomNumberGenerator/methods/randfn'. This means that the function has changed and no compatibility function was provided.
Validate extension JSON: Error: Hash mismatch for 'classes/RenderingServer/methods/environment_set_ambient_light'. This means that the function has changed and no compatibility function was provided.
Validate extension JSON: Error: Hash mismatch for 'classes/RenderingServer/methods/canvas_item_set_canvas_group_mode'. This means that the function has changed and no compatibility function was provided.
Validate extension JSON: Error: Hash mismatch for 'classes/RenderingServer/methods/force_draw'. This means that the function has changed and no compatibility function was provided.
Validate extension JSON: Error: Hash mismatch for 'classes/Window/methods/popup_centered_ratio'. This means that the function has changed and no compatibility function was provided.
Validate extension JSON: Error: Hash mismatch for 'classes/Window/methods/popup_centered_clamped'. This means that the function has changed and no compatibility function was provided.

And finally 4.0.0 has a few more changes where no compat code can be created:

Validate extension JSON: Error: Field 'classes/MenuBar/properties/start_index': type changed value in new API, from "bool" to "int".
Validate extension JSON: Error: Field 'native_structures/PhysicsServer3DExtensionMotionCollision': format changed value in new API, from "Vector3 position;Vector3 normal;Vector3 collider_velocity;real_t depth;int local_shape;ObjectID collider_id;RID collider;int collider_shape" to "Vector3 position;Vector3 normal;Vector3 collider_velocity;Vector3 collider_angular_velocity;real_t depth;int local_shape;ObjectID collider_id;RID collider;int collider_shape".
Validate extension JSON: Error: Field 'native_structures/PhysicsServer3DExtensionMotionResult': format changed value in new API, from "Vector3 travel;Vector3 remainder;real_t collision_safe_fraction;real_t collision_unsafe_fraction;PhysicsServer3DExtensionMotionCollision collisions[32];int collision_count" to "Vector3 travel;Vector3 remainder;real_t collision_depth;real_t collision_safe_fraction;real_t collision_unsafe_fraction;PhysicsServer3DExtensionMotionCollision collisions[32];int collision_count".

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Additionally a bunch of virtual methods have changes between 4.0 and 4.1 but they are currently not validated.
Check misc/extension_api_validation/*.expected for up to date details.

[dsnopek]

Thanks, these look great!

I manually tested the compatibility function for RichTextLabel::push_list() and it worked perfectly. I didn't test any of the others, but skimming the code, it all looks good to me :-)

[dsnopek]

Discussed at the GDExtension meeting, and it looks good!

Otherwise this just needs to be rebased after PR #76446 is merged, and then the remaining commits squashed into one commit, and then we'll approve it!

[RedworkDE]

Added more of the same, 3 more PR with similar breaking changes have been merged since.

And #69988 has removed a whole bunch of APIs but I didn't do anything about that (also IIRC these apis were marked experimental before anyways)

[dsnopek]

The latest updates look good to me!

[fire]

@TokageItLab Protected methods were made public, can we check the AnimationNode? Maybe they need to be private.

[YuriSizov]

Needs a rebase, by the way.

[YuriSizov]

2. I added a second commit that avoids polluting the headers with the compatibility methods, by allowing binds with an explicit this parameter ala bind_function for builtin classes. It is a separate commit for now, as I am not sure if the changes in method_bind.h (tho pretty straight forward) are worth it or if these changes should better be moved to a different PR.

This is something I'd like @reduz to sign off on, so I think moving this to a different PR makes sense.

[dsnopek]

Assuming we don't end up reverting PR #77410, we've now pretty completely broken compatibility with GDExtensions built for Godot 4.0, which makes these compatibility methods not very useful for Godot 4.1.

That said, this work in general is still very useful, as it helps figure out exactly how we're going to add these going forward! And I still really support the idea of using the compatibility method system ASAP, so that we can get some valuable practice with using it.

[YuriSizov]

@dsnopek So what do you think we should do with this PR then? Reject it, but return to it post 4.1? Or merge anyway as a reference point?

[dsnopek]

So what do you think we should do with this PR then? Reject it, but return to it post 4.1? Or merge anyway as a reference point?

That's a good question.

Maybe leave it be for a little while as we watch how things turn out after #77410? But assuming that all turns out good, I'd personally probably lean towards "Reject it, but return to it post 4.1?" It doesn't really make sense to merge code that won't ever get used, and I'm sure we'll have no shortage of compatibility methods to add after 4.1 stable is out.

What do others think?

[YuriSizov]

I guess we can leave it be for now, so when we need to make a 4.1+ version, we have a starting point. I'll turn it into a draft for now.

[RedworkDE]

Closing as there are probably enough compat methods in the engine so that this is no longer needed as reference.

[YuriSizov]

Indeed, but still thanks for work and for providing everyone with a framework!