E-Prime provides support for touchscreens and other touch interfaces (e.g., finger or stylus input on a Tablet PC) through use of the Mouse Device. If no touch-sensitive surface is available during an experiment, touch functionality is disabled.
When a finger or pen/stylus is used for response input on a touch-sensitive surface (i.e., the finger/stylus comes in contact with the surface), the response is processed as a press event (i.e., press of the left mouse button). Loss of contact with the touch-sensitive surface is then processed as a release event. If display of a cursor is turned on, the cursor position is updated to reflect the point of touch/release.
When no finger or stylus is in contact with the screen, the mouse (if present) maintains the ability to move the cursor and generate responses. Typically, if both a mouse and finger/stylus are available, the finger or stylus will take priority over the mouse, but this is hardware and operating system-dependent. E-Prime does not support simultaneous use of the mouse and finger/stylus, and could result in undefined behavior, such as the override of one input source by another, or unexpected cursor behavior.
Additionally, while multi-touch hardware may follow the specification laid out by Microsoft regarding the Primary Contact Point (i.e., first touch point detected), the behavior of multi-touch in an application designed for single touch is operating system-dependent. Multi-touch is not supported by E-Prime, and may result in undefined behavior, such as inaccurate recognition of release events.
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