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This reference is for Processing 3.0+. If you have a previous version, use the reference included with your software in the Help menu. If you see any errors or have suggestions, please let us know. If you prefer a more technical reference, visit the Processing Core Javadoc and Libraries Javadoc.

Name | ### mouseWheel()
Examples |
    void setup() {
      size(100, 100);
    }

    void draw() {}

    void mouseWheel(MouseEvent event) {
      float e = event.getCount();
      println(e);
    }
Description | The code within the mouseWheel() event function is run when the mouse wheel is moved. (Some mice don't have wheels and this function is only applicable with mice that have a wheel.) The getCount() function used within mouseWheel() returns positive values when the mouse wheel is rotated down (toward the user), and negative values for the other direction (up or away from the user). On OS X with "natural" scrolling enabled, the values are opposite. Mouse and keyboard events only work when a program has draw(). Without draw(), the code is only run once and then stops listening for events.
Syntax |
    mouseWheel(event)
Parameters |
event | MouseEvent: the MouseEvent
Returns | void
Related | mouseX mouseY pmouseX pmouseY mousePressed mousePressed() mouseReleased() mouseClicked() mouseMoved() mouseDragged() mouseButton

Updated on January 9, 2020 00:33:08pm EST