[WIP] Add basic import shader support

[fire]

Implements godotengine/godot-proposals#944. Also see #17303. This salvages #17797.

The syntax is import "res://new_shader.shader";

[fire]

Import Shader Project.zip

Example project.

Remaining problems:

1. Caching is incorrect.
2. Nested includes needs a better method.
3. The highlighter sees "res://" as a comment rather as a string.
4. implement as shader_type import;
5. Add compiler errors.

[fire]

@clayjohn mentioned a proposal to make a new shader type import.

shader_type import;

<ClayJohn> [It] can only be included by other shaders. It wouldn't be allowed to have render modes or processor functions.
<ClayJohn> Includes also completely break error reporting. So we would need a more robust shader editor to track errors in included files.

Edited: Don't have much effort on today 2020-08-28. So I'll circle back to the topic at a later date.

Edited:

Changed include to import.

[Ansraer]

Since you have mentioned #17303 and #17797, do you have any intentions to add preprocessor directives to this PR?

[fire]

No.

You can use uniforms and variables for #define and if else statements are already in the language.

[fire]

This needs to be ported to the latest master. It is salvageable, but I am currently lacking effort on it.

The last tasks are to make sure the include detection handles multiple layers correctly.

[MagdielM]

I am interested in salvaging this. As of right now, I've managed to port the changes to c0d01dc and at least gotten around import not being recognized as a shader type. I'll admit I'm not too familiar with how the parser works as of yet, but I care enough about this feature to put in the time.

[CsloudX]

I need this feature too.

[fire]

@MagdielM did you post your work anywhere?

[MagdielM]

@MagdielM did you post your work anywhere?

Oh sorry, after three-or-so weeks of trying to get multiple nesting levels to work and not getting very far, other responsibilities started piling up and I had to put this in the backburner for the time being. I apologize for not mentioning this earlier.

[Calinou]

Oh sorry, after three-or-so weeks of trying to get multiple nesting levels to work and not getting very far, other responsibilities started piling up and I had to put this in the backburner for the time being. I apologize for not mentioning this earlier.

Could you push your updated code to a branch in your fork and link it here? It would likely be helpful if someone is willing to continue this.

Also, I'd argue that even supporting a single level of #include is much better than supporting zero 🙂

[MagdielM]

My work includes a small dependency graph that is supposed to update all included shaders, but I couldn't quite figure out why the parser fails to nest the #includes, so ultimately it doesn't do much.
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