swiping with thumbs

There are different keyboard input methods for smartphones:

• Normal typing

• Thumb typing

• Normal swiping

• Compact (T9) typing

Double input swiping has been explored very little. The only keyboard that I have found to implement a good working solution is keyboard69.

Why is it so uncommon?

• Implementation is hard. Multiple input means there are async processes filling an input buffer that has to be queried for completion candidates on each new event.

• It requires some learning from the user, this make it unattractive, since the higher the learning curve the lesser the user retention.