Optionally leave Unicode characters unescaped in MathML output

[skalee]

This is a feature request. I can provide implementation, but I wanted to discuss things first.

---

MathML does not enforce any particular encoding, UTF-8 is legal, and non-ASCII characters can be used without escaping them [W3C].

However, this gem always encodes non-ASCII characters using numeric XML character references (e.g. é):

asciimath/lib/asciimath/mathml.rb

Lines 234 to 249 in 3a4bbab

	def append_escaped(text)
	text.each_codepoint do |cp|
	if cp == 38
	@mathml << "&amp;"
	elsif cp == 60
	@mathml << "&lt;"
	elsif cp == 62
	@mathml << "&gt;"
	elsif cp > 127
	@mathml << "&#x#{cp.to_s(16).upcase};"
	else
	@mathml << cp
	end
	end
	end
	end

This is safer as it never depends on parent document's encoding, but on the other hand it hampers readability.

My suggestion is to add :escape_non_ascii option to Expression#to_mathml method which would disable this kind of escaping (of course <, >, and & will be escaped anyway). This option should default to false.

Perhaps similar option could be added to Expression#to_html method.

[pepijnve]

I've added the code to do this already. I'm still trying to figure out how I can let users pass options to to_mathml without breaking backwards compatibility. Looks like I've painted myself into a corner there.

[skalee]

Maybe something like:

class Expression
  def to_mathml(prefix = "", attrs = {}, options = {})
  end
end

or:

class Expression
  def to_mathml(prefix = "", attrs_or_escape_non_ascii = nil, attrs_or_nil = nil)
    attrs = #...
    escape_non_ascii = #...
  end
end

or even:

class Expression
  # use like:
  # expr.with_options(escape_non_ascii: false).to_math_ml
  def with_options(options)
    dup.tap do |new_expr|
      # set some options like disabling escaping on expression, which is quite odd, but at least gives reasonable interface
    end
  end
end

Keyword argument would be even better, but I suppose this gem still supports old good Ruby 1.9 for some reason?