laogeodritt

A couple variations on my test cases earlier could get caught up with the linked article’s regex. Since it’s more specific, it’s less likely to happen “in the wild”, but the same idea of “the tag doesn’t match, but (.*?) can match the closing of a tag and opening of a new one” applies.

The code in the linked article adds the rel after the detected href/anchor file type. This position is important to determine what cases will not quite match properly but substitute properly, versus those that will actually fail.

<a href="(.*?).(jpg|jpeg|png|gif|bmp|ico)"><img(.*?)class="(.*?)wp-image-(.*?)" \/><\/a>

A few examples:

<a href="/not/an/image">text</a> more text... later on, an <a href="/image.jpg"><img src="/wp-content/upload/blah.jpg" class="wp-image-111" /></a> – this one technically matches ALL of this text (which is not correct), but still works because the rel gets added to the end of the second <a> opening tag.

<a href="/image.jpg"><img src="image.jpg" /></a> shouldn't be lightboxed (the img doesn't have a class) but is, and then later there's <a href="/image2.jpg"><img src="/image2.jpg" class="wp-image-111" /></a> one of these that should be lightboxed but isn't.

<a href="/image.jpg"><img src="image.jpg" class="not-the-right-class" /></a> shouldn't be lightboxed (the img has the wrong class) but is, and then later there's <a href="/image2.jpg"><img src="/image2.jpg" class="wp-image-111" /></a> one of these that should be lightboxed but isn't.

You can find another example that forces the last (.*?) to match too widely again. The “simple” (but again not 100%) solution to fix this kind of regex would be to use a character class instead of the dot: for example, if you’re inside quotation marks, ([^"]*?) would cover a much larger number of situations (since it can never match outside the ending quotation mark). If you’re inside an HTML tag, ([^>]*?) will never go beyond the tag’s end (but if an attribute value contains a >, which is valid IIRC for some attributes, this one will break).

Also note that this regex does not match single quotes around an attribute value, which are valid in HTML5.

I would honestly recommend not matching only “wp-image-*” classes, though, as power users may write their own markup or include images uploaded elsewhere via FTP, rather than necessarily use the Media Manager. (For example, I personally use the Media Manager for images included in blog posts, but I manually upload images that go into Pages so I can better organize them, while still wanting the lightbox plugin to affect it.)

As for the backtrack limit, honestly it’s not very likely for most users, since the default is 100,000 (kind of low, but not going to be hit unless someone has a gigantic article), and in I think PHP 5.3+ it’s 1 or 10 million (probably not even a concern for any realistic article size). It’s good practice to catch errors if they do happen (as in my case), but the low backtrack limit was just an oversight on my part when I was editing the php.ini settings.

For the error, trigger_error with a warning might be good enough for technically experienced WordPress/PHP users. However, if you can somehow report it on the page or in the admin panel (and take measures so that the error doesn’t break that page entirely), that’d probably be better for the majority of users.

Best regards,

Laogeodritt

Hi Nick, thanks for the reply. (Oops, did I get your name wrong earlier? Looking back I have no idea where I got ‘Phil’ from. Sorry!)

The problem in the linked thread is an add to Google/iCal export for each independent event (where the Event Builder can be used). In this case we’d like to just link to the Calendar as a whole, to add our calendar to the user’s own list of calendars (“Other Calendars” on the GCal page).

Like I mentioned, we have it working with an external text widget for the sidebar containing a link, and just a manual link on the pages that contain the calendar shortcode. This solution is fine for us.

I mentioned this as a feature request because I thought it might be a nice convenience, and one that may be useful to a good proportion of users, to have it as an option to automatically generate that link before/after the events display (calendar, list, etc.) itself, rather than placing it manually.

Regards,

Laogeodritt