TextBox.prototype.addCharacter = function (chr) {
    var startStr = "";
    if (this.caretPos > 0) {
        startStr = this.curText.substr(0, this.caretPos);
    }

    var endStr = "";

    if (this.caretPos < this.curText.length) {
        endStr = this.curText.substr(this.caretPos, (this.curText.length - this.caretPos));
    }

    this.curText = startStr + chr + endStr;
    this.caretPos += 1;

    var curTotalLength = UI.measureString(this.curText);
    if (curTotalLength <= 230) {
        this.visibleText = this.curText;
        this.visibleTextStart = 0;
    } else {
        if (this.caretPos === this.curText.length) {
            this.visibleText += chr;
            while (UI.measureString(this.visibleText) > 230) {
                this.visibleText = this.visibleText.substr(1, this.visibleText.length - 1);
                this.visibleTextStart += 1;
            }
        } else if ((this.caretPos - this.visibleTextStart) >= this.visibleText.length) {
            var add = Math.min(this.curText.length - this.visibleTextStart - this.visibleText.length, 3);
            var endIndex = this.visibleTextStart + this.visibleText.length + add;

            this.visibleText = this.curText.substr(this.visibleTextStart, endIndex - this.visibleTextStart);

            while (UI.measureString(this.visibleText) > 230) {
                this.visibleTextStart += 1;
                this.visibleText = this.curText.substr(this.visibleTextStart, endIndex - this.visibleTextStart);
            }
        } else {
            this.visibleText = this.curText.substr(this.visibleTextStart, Math.min(this.curText.length - this.visibleTextStart, this.visibleText.length + 5));

            while (UI.measureString(this.visibleText) > 230) {
                this.visibleText = this.visibleText.substr(0, this.visibleText.length - 1);
            }
        }
    }

    this.updatecaret();
}