Sometimes, Witch may not list all windows in all applications, though it's not predictable when this may happen. Why is it happening, and what can be done about it?

What's going on?

The problem is caused by how Witch communicates with running applications. Witch uses a public API (Application Programming Interface) known as the Accessibility API to get information about open windows in other programs. Unfortunately, the performance of the Accessibility API is a bit variable at times–most apps reply to our "which windows do you have open?" inquiry in tiny portions of a second, but sometimes, they don't.

If an app doesn't respond quickly, we've got a decision to make: do we wait additional time for the program to answer our query, or do we go ahead without a response from that program? If we wait, that means the Witch panel won't appear onscreen until those programs reply...if we don't wait, it means we're not going to be able to show window information for that program, as we don't know the state of its windows. (You may, for example, have manually closed a window in a program that's not responding to our inquiry.)

So Witch tries to strike a balance–it waits what it considers a reasonable amount of time, then goes ahead and displays the panel. By default, the "reasonable amount of time" is two-tenths of a second. Any program that doesn't answer Witch's query in that timeframe won't have its windows listed in Witch's switching panel.

There's another possible cause of this problem, too: the Accessibility API can only get information from windows that have titles. Draft messages in Mail that are saved without a subject line, for instance, won't appear. Sparrow, a Gmail client for the Mac, also doesn't use window titles, so we can't get its information either. Basically, if a window doesn't have a title, Witch won't be able to find information about that window.

When does this happen?

It's hard to predict, but in general, you'll see this problem most often with apps that are busy -- Safari with a bunch of tabs open, all running video playback, for example. It also tends to crop up more with apps that have had a long "shelf life" in code, such as iTunes and the Office 2004/2008 apps. In Office 2011, Excel, PowerPoint, and Word all seem to work fine, but Outlook is troublesome. (So much so that it has its own knowledge base entry.)

What can be done about it?

You can try modifying the "App response timeout" slider on the Advanced tab in Witch 4 (on the Behavior tab in Witch 3):

The problem with changing this slider is that as you increase the timeout delay, you're increasing the amount of time before the Witch panel appears. At some point, it just makes sense to give up on the troublesome windows, so you see the switcher in a reasonable amount of time.

How can I help?

If you find programs that vanish, beyond those listed here, please email us; we'll see if we can work with the developers to fix the problem.