XChangePointerControl, XGetPointerControl - control pointer
int XChangePointerControl(Display *display, Bool
    do_accel, Bool do_threshold, int accel_numerator, int
    accel_denominator, int threshold);
int XGetPointerControl(Display *display, int
    *accel_numerator_return, int *accel_denominator_return, int
    *threshold_return);
  - accel_denominator
- Specifies the denominator for the acceleration multiplier.
- accel_denominator_return
- Returns the denominator for the acceleration multiplier.
- accel_numerator
- Specifies the numerator for the acceleration multiplier.
- accel_numerator_return
- Returns the numerator for the acceleration multiplier.
- display
- Specifies the connection to the X server.
- do_accel
- Specifies a Boolean value that controls whether the values for the
      accel_numerator or accel_denominator are used.
- do_threshold
- Specifies a Boolean value that controls whether the value for the
      threshold is used.
- threshold
- Specifies the acceleration threshold.
- threshold_return
- Returns the acceleration threshold.
The XChangePointerControl function defines how the pointing device moves.
  The acceleration, expressed as a fraction, is a multiplier for movement. For
  example, specifying 3/1 means the pointer moves three times as fast as normal.
  The fraction may be rounded arbitrarily by the X server. Acceleration only
  takes effect if the pointer moves more than threshold pixels at once and only
  applies to the amount beyond the value in the threshold argument. Setting a
  value to -1 restores the default. The values of the do_accel and do_threshold
  arguments must be True for the pointer values to be set, or the
  parameters are unchanged. Negative values (other than -1) generate a
  BadValue error, as does a zero value for the accel_denominator
  argument.XChangePointerControl can generate a BadValue
  error.
The XGetPointerControl function returns the pointer's
    current acceleration multiplier and acceleration threshold.
  - BadValue
- Some numeric value falls outside the range of values accepted by the
      request. Unless a specific range is specified for an argument, the full
      range defined by the argument's type is accepted. Any argument defined as
      a set of alternatives can generate this error.
Xlib - C Language X Interface