mousePressed() / Reference / Processing.org

Name

mousePressed()

Description

The mousePressed() function is called once after every time a mouse button is pressed. The mouseButton variable (see the related reference entry) can be used to determine which button has been pressed.

This function can be called with or without a MouseEvent parameter. When called with the parameter, you get access to additional information about the mouse event, including the exact coordinates, which button was pressed, and any modifier keys (Shift, Ctrl, Alt, Meta) that were held down. For most simple interactions, the global variables (mouseX, mouseY, mouseButton) provide sufficient information.

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.

Examples

// Click within the image to change 
// the value of the rectangle

int value = 0;

void draw() {
  fill(value);
  rect(25, 25, 50, 50);
}

void mousePressed() {
  if (value == 0) {
    value = 255;
  } else {
    value = 0;
  }
}

// Example showing MouseEvent parameter usage
// Click with different buttons and modifier keys

void setup() {
  size(200, 200);
  background(220);
}

void draw() {
  fill(0);
  textAlign(CENTER);
  text("Click with different buttons", width/2, 20);
  text("Hold Shift, Ctrl, or Alt", width/2, 35);
}

void mousePressed(MouseEvent event) {
  // Get coordinates from event (unaffected by windowRatio)
  int x = event.getX();
  int y = event.getY();
  
  // Get which button was pressed
  int button = event.getButton();
  
  // Check modifier keys
  boolean shift = event.isShiftDown();
  boolean ctrl = event.isControlDown();
  boolean alt = event.isAltDown();
  
  // Set color based on button
  if (button == LEFT) fill(255, 0, 0);
  else if (button == RIGHT) fill(0, 255, 0);
  else if (button == CENTER) fill(0, 0, 255);
  
  // Modify based on modifiers
  if (shift) fill(red(color(255)), green(color(255)), blue(color(255)), 100);
  
  // Draw circle
  ellipse(x, y, alt ? 40 : 20, alt ? 40 : 20);
  
  // Print info
  println("Button: " + button + " at (" + x + "," + y + ")");
  println("Modifiers: Shift=" + shift + " Ctrl=" + ctrl + " Alt=" + alt);
}

Syntax

mousePressed()
mousePressed(event)

Parameters

event(MouseEvent)the MouseEvent

Return

void

This work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.