Splitters gone wild

More on trends in OS X user interface design...

I don’t understand what’s happening to splitter bars. (The part where you grab and drag to resize a split view.)

What the HIG says

Here’s what the Human Interface Guidelines has to say on split views.

The splitter bar displays a circular dimple at its midpoint that indicates to the user that it is draggable...

In a metal window, the width of a splitter bar is 7 pixels...

In a standard Aqua window, the width of the splitter bar is 9 pixels...

No surprise

You’ve probably already noticed that splitter bars come in different sizes. (Compare the iTunes splitter bar to the Finder’s, for instance.)

You may not have noticed a couple other details that I just can’t explain:

1. The dimple in the Finder looks different from the dimple used in iTunes. Here they are, magnified:

Subtle, but, you know, it’s light-source stuff, which Apple has historically mastered.

2. In iTunes there is a light-colored border on either side of the splitter bar—but that’s not true in the Finder. (See second graphic above.)

But those differences aren’t that big, really. At least the splitter is still recognizably a splitter.

Where it gets crazy

This goes back to the goodbye-stripes thing...

You will not find in any of Apple’s apps outside of utilities (or Sherlock) a splitter bar that looks like a standard non-metal splitter bar. You won’t see this:

You would expect to see the above in Mail, because Mail is not metal.

Mail’s horizontal splitter bar looks like this:

The drawing is custom, for Mail only as far as I can tell. (No stripes! Gradient! Cool custom dimple! I like it! No kidding—I really do like it.)

But what is really odd to me is the vertical splitter bar, which looks like this:

It’s a one-pixel-wide line separating an area of blue from an area of white.

I can easily explain this from a coolness factor—but I can’t explain it from a usability standpoint, because it’s very difficult to grab such a narrow target. (And it doesn’t resemble a splitter bar at all, so you don’t necessarily realize that you can grab it.) To make up for it, they’ve added a little grab thing at the bottom of the window which is easy to grab. (Which I also, no kidding, really like.)

Here’s the thing—this isn’t the only non-metal app to completely avoid standard splitter bars.

Look at Keynote, for instance. No splitter bar at all, just a grabber at the bottom. But, though similar, it’s different from Mail—in Keynote you can’t grab the splitter bar at all, you have to use the grabber at the bottom.

And then there’s Xcode—also non-metal, and with yet another custom splitter bar.

The trend

The trend is clearly to avoid standard splitters in non-metal windows.

I have no theory to explain it other than as a coolness thing—stripes are not cool, we must not have stripes.

But even still I have trouble explaining Mail’s vertical splitter, which appears to me to be too much of a triumph of coolness over usability. You might like it—heck, I like it too, it’s cool—but is it too much of a usability hit? When is a cool idea not worth it?

Here’s the thing to remember: developers look to Apple for guidance. If Apple’s UI decisions say that it’s okay to sacrifice usability for a distinctive look, then many developers will do that. It’s a long, long way away—but at the end of that particular road is Windows.