Support for relative values for $().css setters (#7345)

[brandonaaron]

This is for ticket #7345. Supporting +=/-= for setting values in $().css.

We might want to share the rrelnum regex with the rfxnum regex from effects.js since they are the same.

Also, this patch doesn't really take other units than pixels into consideration.

[csnover]

Is there a way this could be combined with the pre-existing code in effects.js instead of copy-pasting duplicate code?

[csnover]

Closing after 30 days of no response from submitter.

[jswartwood]

Just a thought to get rid of that (parts[1] === "-=" ? -1 : 1) test...

change regex:
rrelnum = /^(?:([+-])=)?([\d+.-]+)(.*)$/,

css.js
value = parseFloat(parts[1] + parts[2]) + jQuery.css(elem, name);

and possibly... effects.js
end = parts[1] ? parseFloat(parts[1] + parts[2]) + start : parseFloat(parts[2])

[danheberden]

A newer version of this pull req can be found at #297 - Changed the way it parses the string and wrote some improved tests.