// Define a Caption 'class'.
function Caption(message, color, x, y) {

    // Properties.
    this.message = message;
    this.color = color;
    this.x = x;
    this.y = y;

    // Methods.
    this.draw = function() {
        // Draw the caption, using the parameters provided.
        gContextOverlay.beginPath();
        gContextOverlay.rect(this.x, this.y, 180, 40);
        gContextOverlay.fillStyle = this.color;
        gContextOverlay.fill();
        gContextOverlay.lineWidth = 0.5;
        gContextOverlay.strokeStyle = "#505050";
        gContextOverlay.stroke();

        gContextOverlay.font = "10pt Verdana";
        gContextOverlay.fillStyle = "#000000";
        gContextOverlay.fillText(this.message, this.x + 10, this.y + 25);

        /*console.log(gContextOverlay + " Drew caption: "
        + "\'" + this.message + "\' in "
        + this.color + " at " + x + "," + this.y + ".");*/
    };
    this.remove = function() {
        // This actually clears the entire overlay canvas,
        // but this is invoked with {button}.remove() in showCaption(event).
        gContextOverlay.clearRect(0, 0, gDemoOverlay.width, gDemoOverlay.height);
    };
}

/* A new Caption is defined like this: */
var y = new Caption("Y button - Show caption", "#FFFF66", 270, 90);