Anchors on figures and listings

[elbow-jason]

I have noticed that there are anchor tags on sections and subsections. It would be nice to have anchor tags on the figures' names as well. For example (from the book):

Listing 5-15: Implementing the can_hold method on Rectangle that takes another Rectangle instance as a parameter

The text Listing 5-15 would be a clickable/fragment-navigable link just like sections and subsections.

[carols10cents]

Yep! I've often wanted this myself. I'm not sure the best way to implement this, and since this doesn't affect print at all, it'll be a while before Steve or I has time to work on this. So if someone wants to help out on this, that would be awesome!

[pduzinki]

I'd like to claim this one.

[Michael-F-Bryan]

Would it make sense to incorporate this into mdbook's HTML renderer? For example, whenever including images we could also automatically insert an anchor tag or id which uses a "slugified" version of the figure's alt text.

For example,

![Listing 5-15](img/listing_5_15.png)

would be translated into

<img src="img/listing_5_15.png" alt="Listing 5-15" id="listing-5-15" />

Then whenever you want to refer to that image you'd be able to use its id

For example, as seen in [Listing 5-15](#listing-5-15), blah blah blah.

cc: #1092

[carols10cents]

The problem is these aren't usually images, they're code blocks, and it's not every code block :-/

[Michael-F-Bryan]

I had a feeling that'd be the case when I saw the word "listing", but it was worth a shot :)

[steveklabnik]

The fix for this had to be reverted, so I'm re-opening it.

[mianlang]

Hi everyone, I think I've added anchors to the listings in #4271. Would anyone like to review it?