Test for Technique G21: Ensuring that users are not trapped in content

[hannolans]

http://www.w3.org/TR/2014/NOTE-WCAG20-TECHS-20140408/G21
The objective of this technique is to ensure that keyboard users do not become trapped in a subset of the content that can only be exited using a mouse or pointing device. A common example is content rendered by plug-ins. Plug-ins are user agents that render content inside the user agent host window and respond to all user actions that takes place while the plug-in has the focus. If the plug-in does not provide a keyboard mechanism to return focus to the parent window, users who must use the keyboard may become trapped in the plug-in content.

Procedure

• Tab through content from start to finish.
• Check to see that keyboard focus is not trapped in any of the content.
• If keyboard focus appears to be trapped in any of the content, check that help information is available explaining how to exit the content and can be accessed via the keyboard.

QUAIL

The procedure doesn't describe situations where you enter information (autocomplete etc or enter), that will open modals etc. This test seems focused around plugins. It is a general technique, not a HTMLtechnique. The HTML technque for Flash objects is described in the FLASH17 technique

This technique is describing a failure situation and looks like the counterpart of F10.
As such we can make a doable precondition test:
if no objects or applets are used -> F10 pass, G21 pass
if objects or applets are used: F10 cantell, G21 canttell