Introduce geometry primitives

[Caellian]

Changes

This PR introduces point and rect primitives and replaces previous value pairs with them. It also replaces output-wayland.cc rectangle as it's effectively doing the same.

This aims to make future changes more consistent and to reduce number of global variables by grouping them. As a side bonus, it allows us to optimize some common operations a little by relying on Vc to make the compiler more aware of available opportunities to parallelize computation. Just grouping things results in significant reduction in number of generated move instructions:

Details

• Added vec and rect structures.
• Added Vc dependency for better SIMD optimization of common vector operations.
  • This was previously done through Eigen, but I removed Eigen as 90% of its functionality wouldn't ever be used by Conky so it only added to maintenance burdain.

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[Caellian]

@brndnmtthws Is it okay to add Eigen as dependency? I can do without it, but it might optimize some instructions. Alternatively, I could make it optional and apply SIMD only if present.

EDIT: We do surprisingly many vector computations while drawing components. I don't use majority of Eigen though. It might be better to simply add a way to provide optimized assembly for certain architectures and data types. 🤷‍♂️ And then someone can easily add optimizations later if they want to.

[Caellian]

Last commit is expected be functionally equivalent to original. Besides noted exceptions.

[brndnmtthws]

👍 , seems like Vc is a better choice than Eigen for our needs.

This is a pretty big change, so it's probably going to have some unintended side effects. There are a few things I'd refactor, but probably better to do it in a separate PR later.

[Caellian]

There are a few things I'd refactor, but probably better to do it in a separate PR later.

Same here 😆, I just tried adding semantics to rectangle via tempates (absolute vs. sized) and realized there's a lot that could be improved. C++ doesn't have traits as Rust does so it's somewhat tricky to get things like swizzling to layer properly and still allow the compiler to optimize code.

I'll probably address those issues at some point, but it's better to have something and I don't want to keep this PR waiting for too long as it will be painful to update.