// processing IDE 3.5.3
// button tutorial 
// http://kll.engineering-news.org/kllfusion01/articles.php?article_id=166

// we have already a simple class for ONE Button,
// but there is one step more, what brings it closer to the objects / elements you might know from some libraries.
// a button what can draw itself ( no need to call it in/from draw() )
// also has its own key and mouse functions registered

// but all this also has its disadvantages, besides the overhead,
// if you not need it anymore how you stop it? you need to make a add show / hide method ...


Button myButton = new Button(this, 100, 100, 80, 30, false, "text", 0); // make a button of type class Button

void setup() {
  size(300, 300);
}

void draw() {
  background(200, 200, 0);
}

void keyPressed() { // test button disable
  if ( key == 's' ) myButton.setShow(true);  
  if ( key == 'h' ) myButton.setShow(false);
}


public class Button { //________________________________________ begin class BUTTON
  PApplet pa;
  int x, y, w, h, id;
  boolean click=false, sel;
  String atext;

  boolean showit=true;

  Button(PApplet pa, int x, int y, int w, int h, boolean sel, String atext, int id) {
    this.pa = pa;
    this.x = x;
    this.y = y;
    this.w = w;
    this.h = h;
    this.sel = sel;
    this.atext = atext;
    this.id = id;

    pa.registerMethod("draw", this);
    pa.registerMethod("mouseEvent", this);
    pa.registerMethod("keyEvent", this);
  }

  public void draw() {
    if ( this.showit ) {
      if (this.sel)       fill(0, 200, 0); //___________________ ON OFF fill color
      else                fill(0, 0, 200);
      if (this.over())    stroke(200, 0, 200); //_______________ hover stroke color
      else                stroke(0, 200, 200);
      strokeWeight(3);
      rect(this.x, this.y, this.w, this.h); //__________________ button area as rectangle
      noStroke(); //____________________________________________ button text ( here only one )
      fill(200);
      text(this.atext, this.x + 10, this.y + this.h  - 10);
    }
  }

  public void setShow(boolean set) {
    this.showit = set;
  }

  public boolean  over() {
    return (mouseX > this.x && mouseX < this.x + this.w && mouseY > this.y && mouseY < this.y + this.h);
  }

  public void mouseEvent(MouseEvent m) {   // from @quark
    if ( this.over() ) {
      switch (m.getAction()) {
      case MouseEvent.PRESS:
        this.sel = !this.sel; //________________________________ toggle memory
        break;
      case MouseEvent.RELEASE:
        //
        break;
      }
    }
  }

  // the keyboard input we not use, just prepare
  public void keyEvent(KeyEvent e) {   // from @quark
    int keyCode = e.getKeyCode();
    char keyChar = e.getKey();
    int keyID = e.getAction();
    if (keyID == KeyEvent.PRESS  ) keyPressedProcess(keyCode, keyChar);
    if (keyID == KeyEvent.RELEASE) keyReleasedProcess(keyCode, keyChar);
  }
  // here we use .sel like a focus for test
  protected void keyPressedProcess(int keyCode, char keyChar) {
    if ( this.sel ) println("Button: "+this.id+"  keyPressed, key "+keyChar);
  }

  protected void keyReleasedProcess(int keyCode, char keyChar) {
    if ( this.sel ) println("Button: "+this.id+"  keyPressed, key "+keyChar);
  }
} //_____________________________________________________ end class