Allow the footnote backlink glyph to be changed

[bdesham]

Kramdown uses “↩” (U+21A9) to link from footnotes back to the main text. Under OS X 10.10.3 and iOS 8.3, though, this character appears in Emoji form (↩️, if your browser supports it). Like John Gruber, I’d like to replace the bare U+21A9 with the two-character sequence U+21A9 U+FE0E, which will force it to render in “text style”. (That’s what I did in the the first sentence of this paragraph.)

Would it be possible to add a configuration option so that kramdown uses ↩︎ as its footnote backlink “character”? Alternately, it might make sense just to make this sequence the default; I’d guess that more people prefer the old style symbol to the emoji symbol.

(This feature request is copied from this Stack Overflow question.)

[bdesham]

If you want to go the “change the symbol by default” route, pull request #248 does that.

[gettalong]

I'm sorry that Apple decided to do some bad things. However, if I follow the reasoning I would need to replace, for example, the digit "2" with the sequence "\u0032\uFE0E" because Apple might decide to display the "2" character as emoji... See http://www.unicode.org/Public/UCD/latest/ucd/StandardizedVariants.html

So your reasoning for introducing a new option doesn't quite convince me. If Apple introduced the bug, it should fix it.

However, since this is a real problem for you at this moment, you can change the default output of the HTML converter in one of two ways:

• Post-process the output, which in your use case would look like Kramdown::Document.new(text).to_html.gsub(/\u21a9/, "\u21a9\ufe0e")
• Create a new custom HTML converter that creates the HTML output you want by default.

[gettalong]

Btw. this is how it is supposed to look like in my opinion, ie. the standard codepoint rendered normally and the one with the emoji variant rendered as emoji (browser is Firefox):

[bdesham]

I agree that the non-emoji form should be the default for symbols that were present in Unicode before emoji were added. My feature request was pragmatic, not idealistic 😄

[ole]

I’d just like to add my vote to this request. I understand @gettalong’s reasoning to blame Apple for this and to not change the default, but beside the variation selector I imagine there are many valid reasons why someone would like to change the string that is used as the footnote backlink. For example, someone might not like the arrow symbol at all and prefer a text link like "Go back".

I’d love it if this was a configuration option.

[gettalong]

The way to change the default HTML output of kramdown is to subclass the HTML converter and change what you need. If you are not directly using kramdown but via another library or application it is their job to provide output customizability.

If I provide an option for changing the footnote backlink, I would also need to provide other options for customizing other, static parts of the HTML output (or more correctly, if someone asked for such an option there would be no good reason not to implement it because of the precedent) - and these options can lead to performance penalties.

If I find a good way (I'm open for suggestions!) to handle such cases, this may change in the next major version.

[bdesham]

Are there really many other “static parts of the HTML output”? I mean, the vast majority of the HTML output is dictated by HTML’s syntactic and semantic constraints; the backlink indicator is the only one I can think of that’s more or less arbitrary.

(You could argue that we use ↩︎ out of convention, but in that case we should add the text-mode selector so that the display remains the same even as browsers change how they render things.)

[gettalong]

@bdesham Actually, you are right, there aren't that many static parts - I should have looked at the code first (this is what happens when you don't work with your own code for some time ;-).

The only static parts are in the TOC and footnote output. So if we can agree that the overall output of those two can only be changed by subclassing and not by an option, we could add an option for the footnote backlink.

However, there is a big but: What should be allowed? I guess the option may just contain text, no formatting because otherwise there could be script injection problems. - Any thoughts?

[ole]

Sounds great to me (but I’m biased because I like the option to customize the footnote backlink). I also think text only for the content is a good strategy.