### Bug fixes

Don't use the global `document` variable to track focus, since that doesn't work in another window/frame.

Fix an issue where key handlers that didn't return true were sometimes called twice for the same keypress.

Avoid editing glitches when using deletion keys like ctrl-d on iOS.

Properly treat characters from the 'Arabic Presentation Forms-A' Unicode block as right-to-left.

Work around a Firefox bug that inserts text at the wrong point for specific cross-line selections.