HTML unicode escaping sequences

[Dakror]

Like discussed in #399 , implementing HTML unicode unescaping seems more sensible right now than CSS-based.

This PR implements both decimal and hex decoding of html entities.

[mikke89]

Nice work, this will be good to have!

Did you try to benchmark this? I don't expect any major trouble, but it would be nice to be sure, especially for documents with a lot of text. We could also avoid copies by taking strings by value and moving, but let's see what the profiler says first.

[Dakror]

I performed a benchmark with a modified version of the element benchmark and verified no performance decrease

[mikke89]

Thank you!
I did some profiling earlier, and I got around 4% performance impact for the decoder during SetInnerRml (6% if we include when it runs for attributes). I think this is acceptable as it shouldn't make a huge difference in practical cases, although it would be something to try to improve later.

I was about to merge this, but I just thought about a potential issue. The decoding happens before checking for RML tags. So if I am correct, submitting e.g. <p> will actually create a new <p> element. It is also recursive, so if we e.g. submit <p>&amp;lt;</p> it will turn into a <p> element with the text < instead of <. And so on...

[Dakror]

I think my latest commit fixes that issue. What do you think?

[mikke89]

Yup, I think it does!

However, the new test actually demonstrates another issue:

CHECK(StringUtilities::StripWhitespace(document->GetInnerRML()) == "<p>&lt;span/&gt;</p>");

This would be correct if we returned the inner text (you can use ElementText::GetText for that). However, this is supposed to return the RML - but if you pass this back to SetInnerRml then this creates a <p> element containing the text. I think we need to RML-encode the value returned from a text element's GetInnerRml.

[Dakror]

True, we need to reverse the decoding to stay correct

[mikke89]

Here we go, thanks!

[xland]

Should Document be updated?

[mikke89]

You're right, the documentation should be updated. I just made some changes and additions to the RML documentation. In particular, I wrote a new page on the RML syntax.