A multi-touch system is disclosed that recognizes simultaneous touchdown
of four fingers on, above, or below the home row of keys as a modifier
chord and applies modifiers such as Shift, Ctrl, or Alt to subsequent
touch activity until none of the chord fingertips remain touching.
Touches by the thumb of the modifier chord hand that occur before any
modifiable typing or clicking activity cause the modifier chord to be
canceled and reinterpreted as hand resting. The Shift modifier may be
released temporarily during thumb keypresses that are intermixed with
typing of capitalized characters. Distributing the modifier chord touches
across different zones or key rows selects multiple modifiers. In an
alternative embodiment, different modifiers can be selected with
different arrangements of the fingers relative to one another within the
chord, irrespective of absolute hand alignment with the touch surface.