CodeRay

It turns out that a simple, line-based version was quite easy to implement. Commit follows.

We need nicer token color blending for this (eg. strings on insertions), as the new Alpha style provides.

It determines the language based on the filename in the header, and looks awesome - see screenshot.

The only thing missing for now is Tokens#split_into_lines.

Maybe what we need is more like Tokens#each_line?

Rather than having it as a title text would it be possible for it to just highlight the change similar to the way github does it: http://github.com/rails/rails/commit/4e75cc59e70947b794c96894d39c015f9e1cb96c#L0L143
?

That might be possible, but it would be necessary to implement a diff mechanism into the scanner. Also, with the new code-inside-diff highlighting, the change could begin or end in the middle of a token that is served by another scanner, which makes it more complicated.

I think this should be another ticket. Can you open one?

I really like your idea! It has to be carefully combined with other features of CodeRay. Most importantly, it may not be a good idea to highlight the changed portion with a background tint, like github does - because, with the new file-based highlighting inside the diff code, we already have a tint for the changed line (red or green) and possibly for strings, strings inside strings, and so on. Using the new Alpha style (which uses CSS 3 colors) it's technically possible to stack three or more of those transparent background colors, but I think there's a better way.

This way is using boxes. A thin red or green border around the change could highlight it without changing the background color. I haven't been able to find a nice diff library for Ruby, though. Diff-LCS and differ don't seem work with strings like this.

Looking at GitHub's diff highlighting, I noticed several things:

• It doesn't highlight inline changes in gists, only for changesets.
• Only single-line changes seem to be handled this way. If a change covers two or more consecutive lines, it doesn't highlight the changes inline.
• There seems to be only one highlighted part per line, and it's determined by matching the lines from the beginning and from the end until a difference is detected. It's a quite simple algorithm, yet quite useful, as you pointed out.

Kornelius Kalnbach wrote:

That might be possible, but it would be necessary to implement a diff mechanism into the scanner. Also, with the new code-inside-diff highlighting, the change could begin or end in the middle of a token that is served by another scanner, which makes it more complicated.

I think this should be another ticket. Can you open one?

New ticket here: #227

The new Diff scanner now has all the features I planned, but it'll need more testing.