// fadetoy
//    -- experiments with transparency and fading
//
//  Scott "Jerry" Lawrence
//  http://www.cis.rit.edu/~jerry/Software/p5
//

// previous mouse positions
int px = 0;
int py = 0;

boolean start = true; // first time through loop()?

// set up our junk
void setup()
{
  size( 200, 200 );
  noBackground(); // don't clear with each frame

  colorMode( RGB, 255, 255, 255, 255 ); // note the 4th '255' for transparency/alpha
  ellipseMode( CENTER_DIAMETER ); // draw ellipses from the center

  // clear the screen
  fill( 0, 0, 0, 255 );
  rect( 0,0, width, height );  
}


// do some stuff
void loop()
{
  int x = mouseX;
  int y = mouseY;
  
  if( start )  // this eliminates the "ellipse from 0,0" bug
  {
    px = x; py = y;
    start = false;
  }
  
  // draw lines if the button is down, otherwise draw ellipses
  if( mousePressed )
  {
    stroke( 0, 255, 255, 255 );
    line( px, py, x, y );
  } else {
    fill( 255, 0, 255, 100 );
    ellipse( x, y, abs(px-x)+2, abs(py-y)+2 );
  }
  
  // try a transparency fade
  noStroke();
  int s = second();
  if( (s&7) > 3 )
  {
    // fade to white
    fill( 255,255,255, 10 ); // increase 10 to speed it up, decrease to slow down
    // due to integer transparency, (255,50,0,10) will leave lingering shadows
  } else {
    // fade to black
    fill( 0, 0, 0, 10 );
  }
  rect( 0, 0, width, height ); // draw it
  
  // store our mouse positions for the next iteration
  px = x;
  py = y;
  
  // screengrab stuff
  /*
  if( keyPressed )
  {
    if( key == 'G' )
       screenGrab();
  } */
}