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# 14.2 Pointer Control

The following paragraphs describe the CLX functions used to:

- Return or change the pointer acceleration and acceleration threshold
- Return or change the mapping of pointer button numbers

change-pointer-control | display &key :acceleration :threshold | Function

| display A display. :acceleration A number for the acceleration ratio. :threshold The number of pixels required for acceleration to take effect. Changes the acceleration and/or the acceleration threshold of the pointer for the display. The :acceleration number is used as a multiplier, typically specified as a rational number of the form C/P, where C is the number of pixel positions of cursor motion displayed for P units of pointer device motion. The acceleration only occurs if the pointer moves more that :threshold pixels at once, and only applies to the motion beyond the :threshold . Either :acceleration or :threshold can be set to :default, that restores the default settings of the server.

pointer-control | display | Function

| display A display. Returns the acceleration and threshold for the display pointer. acceleration, threshold Type number.

pointer-mapping | display &key ( :result-type 'list) | Function

| display A display. :result-type The type of sequence to return. Returns or (with setf) changes the mapping of button numbers for the display pointer. The :result-type is not used when changing the mapping. If element i of the mapping sequence is j, then the events from pointer button j are reported by the server as events for button i+1. (Note that pointer buttons are numbered beginning with one, while the mapping sequence itself is indexed normally from zero.) If element i of the mapping sequence is zero, then button i+1 is disabled and can no longer generate input events. No two elements of the mapping can have the same non-zero value. The length of the mapping sequence indicates the actual number of buttons on the device. When changing the mapping, the new mapping must have this same length. mapping Type sequence or card8.

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