feat: Add a Render Context API

[luanpotter]

Description

This provides a "context" API for components to share render-time information with indirect descendants.

Use cases can include:

• the currentCamera value which is currently handled as a global list
• shader rendering information (to replace the custom Canvas implementation from feat: Post Process API #3404)

Checklist

• I have followed the Contributor Guide when preparing my PR.
• I have updated/added tests for ALL new/updated/fixed functionality.
• I have updated/added relevant documentation in docs and added dartdoc comments with ///.
• I have updated/added relevant examples in examples or docs.

Breaking Change?

• Yes, this PR is a breaking change.
• No, this PR is not a breaking change.

[renancaraujo]

Looking good. API wise it is good enough as an approach that it is not a breaking change.

It seems specific to the render phase, so I would add user-friendly error messages for when users try to access the context outside of render.
Also, should we name it RenderContext since it is so specific?

[luanpotter]

@renancaraujo agree with both!

[spydon]

I'd just like some benchmark of the implication of adding this, other than that I think it looks good!

[github-actions]

Benchmark Results

Package flame:

Benchmarks	Current Branch [luan.context-api]	Base Branch [main]	Diff
Render Components Benchmark	1100.824 μs	1119.342 μs	🟢 -1.654 %
Updating Components Benchmark	387592.667 μs	399562.833 μs	🟢 -2.996 %

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Benchmarks provided with 💙 by Dart Benchmark Action.

[luanpotter]

(note: I will add a bench specifically about rendering when I have some time. this was just testing the waters with the action)

[renancaraujo]

Merge eet

[luanpotter]

@renancaraujo I changed the name - but any idea how I could add a message if findRenderContext is called outside the render phase? only thing I can think of is to create a global counter or something 🙈

[spydon]

@renancaraujo I changed the name - but any idea how I could add a message if findRenderContext is called outside the render phase? only thing I can think of is to create a global counter or something 🙈

I think this is something we can handle by docs instead. So that we mention in both the dartdocs and the docs on the site that it should only be called from within the render-loop. I doubt many end-users will use the render context directly anyways?

[luanpotter]

@spydon agreed. all concerns addressed, should we merge then?

[spydon]

@spydon agreed. all concerns addressed, should we merge then?

🚢-eeeeet!!