Learning Processing: A Beginner's Guide to Programming Images ...

X = �50
fi g. 17.4
float w = textWidth(headline) ;
if (x < -w) {
x = width;
}
Text 313
Example 17-3 is a full example that displays a diff erent headline each time the previous headline leaves
the screen. Th e headlines are stored in a String array .
Example 17-3: Scrolling headlines
// An array of news headlines
String[] headlines = {
" Processing downloads break downloading record. ",
" New study shows computer programming lowers cholesterol. ",
} ;
PFont f; // Global font variable
float x; // Horizontal location
int index = 0;
void setup() {
size(400,200);
f = createFont( "Arial",16,true);
// Initialize headline offscreen
x = width;
}
void draw() {
background(255);
fill (0);
// Display headline at x location
textFont(f,16);
textAlign (LEFT );
text(headlines[index],x,180);
// Decrement x
x = x – 3;
X = 0
Some text
still on screen!
Some text
width = 100 pixels
fi g. 17.5
// If x is less than the negative width,
// then it is off the screen
float w = textWidth(headlines[index]);
if (x < -w) {
x = width;
index = (index + 1) % headlines.length;
}
}
X = �100
Some text
all the way off screen!
If x is less than the negative width, then it is
completely off the screen
Multiple Strings are
stored in an array.
A specifi c String from the array is
displayed according to the value of the
“index” variable.
textWidth() is used to calculate the width
of the current String.
“index“ is incremented when the current
String has left the screen in order to
display a new String.