The following code will track the mouse X position but only print it out if it has changed.

1. int px;
2. 
   
3. public void setup() {
4.   size(300, 300);
5.   px = mouseX;
6. }
7. 
   
8. public void draw() {
9.   background(255);
10.   if (px != mouseX) {
11.     println(px);
12.     px = mouseX;
13.   }
14. }

really cool ! thanks_
an other little question: how could it be possible to make absdiff of a value:
I mean something like: if the value doesn't change, the output is 0. if it 's change, the output is the difference of the value at state : frame+1 and frame0 for instance.
I'm pretty newbie in those things, thanks in advance

deltaX keeps track of the absolute value of the change in px

1. int px;
2. int deltaX;
3. 
   
4. public void setup() {
5.   size(300, 300);
6.   px = mouseX;
7. }
8. 
   
9. public void draw() {
10.   background(255);
11.   if (px != mouseX) {
12.     deltaX = abs(px - mouseX); // absolute difference
13.     println(px + " absoulte change is " + deltaX);
14.     px = mouseX;
15.   }
16.   else {
17.     deltaX = 0;
18.   }
19. }

really clear !
thx