yeuch

drawLine.pde

/*
click and start line
 click and end line
 */

boolean lineStarted, lineFinished;
PVector p0, p1;

void setup() {
  size(300, 300);
  background(0);
  stroke(255);
  lineStarted = false;
  lineFinished = false;
}

void draw() {
  background(0);
  if (lineFinished) {
    line(p0.x, p0.y, p1.x, p1.y);
  } 
  else if (lineStarted) {
    line(p0.x, p0.y, mouseX, mouseY);
  }
}

void mousePressed() {
  if (!lineStarted && !lineFinished) {
    p0 = new PVector(mouseX, mouseY);
    lineStarted = true;
    lineFinished = false;
  } 
  else if (lineStarted) {
    p1 = new PVector(mouseX, mouseY);
    lineStarted = false;
    lineFinished = true;
  }
  else {
    lineFinished = false;
  }
}