1. A computer implemented method of processing a gesture input on a touch screen display device, the method comprising: receiving a gesture input on the touch screen display; recognizing the gesture as invoking an annotation canvas; determining a height and a width of the annotation canvas; displaying the annotation canvas on the touch screen display; responsive to receiving an input gesture within the annotation canvas, interpreting the gesture as an annotation gesture for input an annotation, and executing the annotation gesture; and responsive to receiving the input gesture outside of the annotation canvas, interpreting the gesture as a navigation input.