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The _WHEEL function returns the relative position of a specified wheel number on a controller device.


move = _WHEEL(wheelNumber%)

  • Returns -1 when scrolling up and 1 when scrolling down with 0 indicating no movement since last read.
  • Add consecutive wheel values to determine a cumulative value over time for scrolling or moving objects.
  • wheelNumber% must be a number which does not exceed the number of wheels found by the _LASTWHEEL function.
  • When a mouse indicates it has 3 wheels, the first two are for relative movement reads. The third wheel is for scrolling.
  • The number of _DEVICES must be read before using _DEVICE$, _DEVICEINPUT or _LASTWHEEL.


Example 1: Reading multiple controller device buttons, axis and wheels.

FOR i = 1 TO _DEVICES PRINT STR$(i) + ") " + _DEVICE$(i) + " Buttons:"; _LASTBUTTON(i); ",Axis:"; _LASTAXIS(i); ",Wheel:"; _LASTWHEEL(i) NEXT DO d& = _DEVICEINPUT IF d& THEN ' the device number cannot be zero! PRINT "Found"; d&; FOR b = 1 TO _LASTBUTTON(d&) PRINT _BUTTONCHANGE(b); _BUTTON(b); NEXT FOR a = 1 TO _LASTAXIS(d&) PRINT _AXIS(a); NEXT FOR w = 1 TO _LASTWHEEL(d&) PRINT _WHEEL(w); NEXT PRINT END IF LOOP UNTIL INKEY$ = CHR$(27) 'escape key exit END

Note: When there is no device control to read, a FOR n = 1 TO 0 loop will not run thus avoiding a control function read error.

Example 2: Why does a mouse have 3 wheels? Relative x and y movements can be read using the first 2 _WHEEL reads.

ignore = _MOUSEMOVEMENTX 'dummy call to put mouse into relative movement mode PRINT "Move your mouse and/or your mouse wheel (ESC to exit)" d = _DEVICES ' always read number of devices to enable device input DO: _LIMIT 30 'main loop DO WHILE _DEVICEINPUT(2) 'loop only runs during a device 2 mouse event PRINT _WHEEL(1), _WHEEL(2), _WHEEL(3) LOOP LOOP UNTIL INKEY$ = CHR$(27)

Explanation: Referencing the _MOUSEMOVEMENTX function hides the mouse and sets the mouse to a relative movement mode which can be read by _WHEEL. _DEVICEINPUT(2) returns -1 (true) only when the mouse is moved, scrolled or clicked.

See also

Keyword Reference - Alphabetical
Keyword Reference - By Usage
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