MultiStateButton

class MultiStateButton :
{
  attributes {
    graphicalState : Int = 0;
    boundingBox : Rect;
    onClick : Action;
  }
  operations {
    hitTest(coord : Coord) : Bool {
      return boundingBox.hitTest(coord);
    }
    draw() {
      switch (graphicalState) {
        case (0) {
          // draw unfocused button
        }
        case (1) {
          // draw focused button
        }
        case (2) {
          // draw down button
        }
        default {
          throw new Exception("invalid graphical state");
        }
      }
    }
    updateGraphicalState(nState : int) {
      if (nState != graphicalState) {
        graphicalState = nState;
        draw();
      }
    }
  }
  states
  {
    unfocusedState(e : UnfocusedEvent) {
      entry {
        UpdateGraphicalState(0);
      }
      transitions {
        MouseMoveEvent -> focusingState;
      }
    }
    focusingState(e : MouseMoveEvent) {
      entry {
        if (hitTest(e.coord))
          this.send(FocusedEvent);
        else
          this.send(UnfocusedEvent);
      }
      transitions {
        FocusedEvent -> focusedState;
        UnfocusedEvent -> unfocusedState;
      }
    }
    focusedState(e : FocusedEvent) {
      entry {
        updateGraphicalState(1);
      }
      transitions {
        MouseMoveEvent -> focusingState;
        ButtonDownEvent -> downState;
      }
    }
    downAndFocusedState(e : ButtonDownEvent ) {
      entry {
        updateGraphicalState(2);
      }
      transitions {
        MouseMoveEvent -> movingWhileDownState;
        MouseUpEvent -> clickedState;
      }
    }
    movingWhileDownState(e : MouseMoveEvent) {
      entry {
        if (hitTest(e.coord))
          this.send(downAndFocusedEvent);
        else
          this.send(downAndUnfocusedEvent);
      }
      transitions {
        FocusedEvent -> focusedState;
        UnfocusedEvent -> unfocussedState;
      }
    }
    downAndUnfocusedState(e : ButtonDownEvent ) {
      entry {
        updateGraphicalState(0);
      }
      transitions {
        MouseMoveEvent -> movingWhileDownState;
        MouseUpEvent -> unfocusedState;
      }
    }
    clickedState(e : ButtonUpEvent) {
      entry {
        onClick.invoke(this);
        this.send(UnfocusedEvent);
      }
      transitions {
        UnfocusedEvent -> unfocusedState;
      }
    }
  }
}