F. APPPENDIX F — Using the Simple Pointer Protocol

The Simple Pointer Protocol is intended to provide a simple mechanism for an application to interact with the user with some type of pointer device. To keep this interface simple, many of the custom controls that are typically present in an OS-present environment were left out. This includes the ability to adjust the double-click speed and the ability to adjust the pointer speed. Instead, the recommendations for how the Simple Pointer Protocol should be used are listed here.

X-Axis Movement:

If the Simple Pointer Protocol is being used to move a pointer or cursor around on an output display, the movement along the x-axis should move the pointer or cursor horizontally.

Y-Axis Movement:

If the Simple Pointer Protocol is being used to move a pointer or cursor around on an output display, the movement along the y-axis should move the pointer or cursor vertically.

Z-Axis Movement:

If the Simple Pointer Protocol is being used to move a pointer or cursor around on an output display, and the application that is using the Simple Pointer Protocol supports scrolling, then the movement along the z-axis should scroll the output display.

Double Click Speed:

If two clicks of the same button on a pointer occur in less than 0.5 seconds, then a double-click event has occurred. If a the same button is pressed with more than 0.5 seconds between clicks, then this is interpreted as two single-click events.

Pointer Speed:

The Simple Pointer Protocol returns the movement of the pointer device along an axis in counts. The Simple Pointer Protocol also contains a set of resolution fields that define the number of counts that will be received for each millimeter of movement of the pointer device along an axis. From these two values, the consumer of this protocol can determine the distance the pointer device has been moved in millimeters along an axis. For most applications, movement of a pointer device will result in the movement of a pointer on the screen. For each millimeter of motion by the pointer device in the x-axis, the pointer on the screen will be moved 2 percent of the screen width. For each millimeter of motion by the pointer device in the y-axis, the pointer on the screen will be moved 2 percent of the screen height.