Core: safeBlur breaks in IE11

[Jörn Zaefferer]

This is a regression from a recent change ( ​https://github.com/jquery/jquery-ui/commit/f33027840cdac5152599da66635981bbe68c6bda ), causing three test suites to fail in IE11. From a recent build:

• Dialog: ​http://swarm.jquery.org/result/81652
• Draggable: ​http://swarm.jquery.org/result/80673
• Droppable: ​http://swarm.jquery.org/result/80668

The error is the same for each:

Unable to get property 'toLowerCase' of undefined or null reference

Source: ​https://github.com/jquery/jquery-ui/blob/8bcd363ae640bbefc28b720c1ab58b7992ea7044/ui/core.js#L74

Only dialog and draggable use safeBlur. Can't yet tell why element is defined, but element.nodeName isn't.

[Scott González]

I can't reproduce the failures even when using the TestSwarm URLs.

[Jörn Zaefferer]

Probably related to the iframe TestSwarm uses. There the error is showing up pretty consistently over multiple builds.

[Scott González]

Core: Handle IE11 bug with document.activeElement in iframes

Fixes #11539 Closes gh-1518

Changeset: 76c27556f48bea48d3787c241d35e190d46c3245

[Scott González]

I spent a while trying to reduce this as much as I could, but I gave up after a while. Here's what I came up with: ​http://jsbin.com/fejituname/1/. It still has a dependency on jQuery Core, but it reliably reproduces the bug.

[dmethvin]

What should I see from that test case?

[Scott González]

You should see an alert with an error message in IE11.

[dmethvin]

I don't see an alert in either real Win8.1+IE11 on Windows or on Win7+IE11 Browserstack.

Did I mention I hate focus?

[Scott González]

That's because of the new live preview time limit in jsbin :-/ It loads the editor instead of the actual page now.

[Scott González]

​http://jsbin.com/towote/1 is a new clone of the bin with a registered account, so it should work forever.