Consider providing hash implementation for public types

[dmtrKovalenko]

This will involve some work around the floats to make them hashable. In the case of SVG types I think we can even do the simple .to_bits().hash() with additional check for the NaN value, but also we can use more robust way like https://github.com/reem/rust-ordered-float/blob/master/src/lib.rs

If you accept this I can open a PR

[RazrFalcon]

Can you provide a use case?

[dmtrKovalenko]

Cache individual svg elements rendered canvases based on the declaration

[RazrFalcon]

It would be highly problematic to implement. Not to mention very slow. usvg nodes are very complex. Text alone has like 50 properties.
I would suggest using element IDs, assuming they are present.

In the worst case we could try adding UUID for each node, so it could be used for hash instead.

[dmtrKovalenko]

I already have a fork of your repo with hash implementation and rerendering the element is much slower than hashing every node.

Using ids is not possible because I need to specifically detect if the element was changed.

[RazrFalcon]

Of course rendering is slower, but slow caching isn't a solution either. I will think about it. For now just fork.

Using ids is not possible because I need to specifically detect if the element was changed.

Elements are immutable since recently.