Keyboard Accessibility

[jbb01]

I want to address three issues related to keyboard accessibility of the fixed header here. All of them can be seen in datatables_fixed_header_keyboard.zip.

1. When activating a sort button in the fixed header using the keyboard, focus is lost.
2. When tabbing through the complete page, the header is encountered twice, first in-place and then floating. This is because the fixed header is placed at the end of the body. Ideally, the fixed header should appear at the position in the tab order as the original header. When tabbing through the page in reverse order while the page is scrolled to the top, neither of the two headers will receive focus.
3. Focus is not retained when switching between in-place and fixed header.

[AllanJard]

Thanks for posting this. All good points! The transition from one "mode" to the other is where this should be handled. I'd certainly welcome a pull request to address these points, or I'll get to them when possible.