Example 0 3

[Examples 0] 0 1 2 3 4 5 6 7 8 9
// line between two points
// one fixed, one draggable

int x1 = 120;
int y1 = 80;

int x2 = 240;
int y2 = 160;

void setup() {
  size(360, 240);
  smooth();
  stroke(0);
} //setup

void draw() {
  background(207);
  strokeWeight(3);
  line(x1, y1, x2, y2);
  strokeWeight(1);
  fill(255, 255, 0);
  ellipse(x1, y1, 5, 5);
  fill(255, 0, 0);
  ellipse(x2, y2, 5, 5);
} //draw

void mouseDragged()
{
  x1 = mouseX;
  y1 = mouseY;
} //mouseDragged
Drag one end of line.