Behind unavoidable apps like Photoshop, xScope is one of those tools that nearly every Web designer needs. But even if you haven’t come across the app before, xScope’s measuring, inspecting & testing tools are definitely worth a look if you work for the Internet.

id447661441 xScope: The must have measuring toolkit for Web designers gets a Retina updateNow, creators Iconfactory and ARTIS Software have released a new update for this $29.99 app, bringing in Retina support, as well as subtle changes like invertable ruler colors (for measuring on dark backgrounds), full-screen app support and a number of bug fixes. Of course, the company’s simple description still rings true:

Quickly available via the Mac OS X menubar, xScope’s flexible tools float above desktop windows and UI elements making measuring a breeze

Iconfactory Principal / Designer Gedeon Maheux and Principal / Senior Software Engineer Craig Hockenberry, went into great detail on the challenges they faced while developing this app. You’d think that a Retina update would only involve swapping out high resolution graphics, but some interesting problems came up, particularly involving mouse input, window positioning, pixel alignment and so on. From Hockenberry:

Today we released an update for xScope that supports the Retina display. As I alluded to on Episode 14 of The Talk Show, this update was harder than most. The 68k to PowerPC, Carbon to Cocoa, and PowerPC to Intel transitions were no walk in the park, but this update really kicked my butt. Here’s hoping that sharing some of the things I learned along the way will help you with your own Retina work.

For most developers who are working strictly in window points, an update for the Retina display is a fairly straightforward process. xScope, however, does a lot of work with both pixels and points. And that’s where the fun begins…

Read more for an inside look: here and here.

Screen Shot 2012 09 14 at 12.36.35 PM 520x328 xScope: The must have measuring toolkit for Web designers gets a Retina update

Now, this app costs a sizable $29.99, so if you’re looking for something simpler, you might want to check out SnapRuler ($9.99), which TNW reviewed here. Still, we can’t help but encourage power users to check out xScope via the link below.

➤ xScope, $29.99 in the App Store