How can you add a triangle to the Buttons example ? heres the LINK for the example - http://processing.org/learning/topics/button.html 

 

I tried doing it using the method :

 

int rectX, rectY;      // Position of square button
int circleX, circleY;  // Position of circle button
int triangX, triangY;  // Position of triangle button
int rectSize = 50;     // Diameter of rect
int circleSize = 53;   // Diameter of circle
int triangleSize = 53; // Diameter of triangle
color rectColor, circleColor,triangColour, baseColor;
color rectHighlight, circleHighlight, colour triangHighLight;
color currentColor;
boolean rectOver = false;
boolean circleOver = false;
boolean triangOver = false;

void setup()
{
  size(200, 200 , 200);
  smooth();
  rectColor = color(0);
  rectHighlight = color(51);
  circleColor = color(255);
  circleHighlight = color(204);
  triangColour = colour(47);
  trinagHighlight = colour(102);
  baseColor = color(102);
  currentColor = baseColor;
  circleX = width/2+circleSize/2+10;
  circleY = height/2;
  rectX = width/2-rectSize-10;
  rectY = height/2-rectSize/2;
  triangX = width/2-triangSize-10;
  triangY = height/2-triangSize/2;
  ellipseMode(CENTER);
}

void draw()
{
  update(mouseX, mouseY);
  background(currentColor);
 
  if(rectOver) {
    fill(rectHighlight);
  } else {
    fill(rectColor);
  }
  stroke(255);
  rect(rectX, rectY, rectSize, rectSize);
 
  if(circleOver) {
    fill(circleHighlight);
  } else {
    fill(circleColor);
  }
  stroke(0);
  ellipse(circleX, circleY, circleSize, circleSize);
 
  if(triangOver) {
    fill(triangHighlight);
  } else {
    fill(rectColor);
  }
  stroke(102);
  rect(triangX, triangY, triangSize, triangSize);
}

void update(int x, int y)
{
  if( overCircle(circleX, circleY, circleSize) ) {
    circleOver = true;
    rectOver = false;
    triangOver = false;
  } else if ( overRect(rectX, rectY, rectSize, rectSize) ) {
    rectOver = true;
    circleOver = false;
    triangOver = false;
  } else if (overTriang(triangX, triangY, triangSize, triangSize) ) {
    triangOver = true;
    rectOver = false;
    circleOver = false;
  } else {
    circleOver = rectOver = triangOver = false;
  }
}

void mousePressed()
{
  if(circleOver) {
    currentColor = circleColor;
  }
  if(rectOver) {
    currentColor = rectColor;
  }
  if(triangOver) {
    currentColour = triangColour;
  }
}

boolean overRect(int x, int y, int width, int height)
{
  if (mouseX >= x && mouseX <= x+width &&
      mouseY >= y && mouseY <= y+height) {
    return true;
  } else {
    return false;
  }
}

boolean overCircle(int x, int y, int diameter)
{
  float disX = x - mouseX;
  float disY = y - mouseY;
  if(sqrt(sq(disX) + sq(disY)) < diameter/2 ) {
    return true;
  } else {
    return false;
  }
 
  boolean overTriang(int x, int y, int width, int height)
{
  if (mouseX >= x && mouseX <= x+width &&
      mouseY >= y && mouseY <= y+height) {
    return true;
  } else {
    return false;
  }
}