Partial line highlighting

[kmckee]

Could we add support for partial line highlighting?

Suppose I had the following code block...

for(var i = 0; i<= 10; i++) {
}

I'd like to be able to highlight just the initializer (var i = 0;) using something like this:

<p class="fragment" data-code-focus="1" data-code-focus-columns="4-13">
  Commentary on initializer goes here
</p>

[kmckee]

Or, perhaps the data-code-focus string just becomes a little more complex instead:

<p class="fragment" data-code-focus="1[4-13]">
  Commentary on initializer goes here
</p>

1[4-13] = Columns 4 thru 13 on row 1

[bnjmnt4n]

This seems like a useful feature - but we'll have to rework a lot of the internals and the CSS styling. Currently we just wrap each line with a <span>, and do minimal work on the HTML to avoid messing up highlight.js's own <span> tags. To enable selective highlighting of specific ranges, we'll have to figure out a clean and minimal method of detecting tags and opening them where necessary to avoid overlapping.