Processing: Creative Coding and Computational Art

PROCESSING: CREATIVE CODING AND COMPUTATIONAL ART
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detect which mouse button is pressed (left, right, or center), using Processing’s
mouseButton system variable. With a little help from Java, it can also detect multiple button
clicks, which I’ll illustrate in a sketch at the end of the chapter.
Following is a better mouse event example, in which a rectangle on the screen is moved to
the position of the mouse when the mouse button is pressed. The mouseX and mouseY
properties are used to get the respective x and y positions of the mouse.
// mousePressed function
// example 1
// declare x, y
float x, y;
// declare and initialize w, h
float w = 20.0, h = 20.0;
void setup(){
size(400, 400);
// initialize x, y
x = width/2.0;
y = height/2.0;
rectMode(CENTER);
}
void draw(){
background(255);
rect(x, y, w, h);
}
void mousePressed() {
x = mouseX;
y = mouseY;
}
This example utilizes a function called mousePressed(). Remember, the void in front of
the function identifier just means that the function doesn’t return a value. Processing also
provides an alternative mousePressed Boolean variable that detects whether the mouse is
pressed. The variable is equal to true if the mouse is pressed and false if it’s not. As the
following code shows, the previous sketch can be easily changed to use the mousePressed
variable instead of the mousePressed() function:
// mousePressed variable
// example 2
// declare x, y
float x, y;
// declare and initialize w, h
float w = 20.0, h = 20.0;