This almost works like I wanted it to. The "problem" is this:
1. Type text until box is full
2. Move cursor to the middle of the text
3. Type one character
Result: character is added in the middle of the string, last character of the string is deleted
Expected: should not be able to type that character in the middle.
I believe I'll manage to make it work by using some instance variable to store the "last known good" string, but I think a "MAXLENGTH" property would be great to have on text boxes.