// An extremely minimal text editor, it can only insert
// and remove characters from a single line
PFont font;
String letters = "";

void setup() {
  size(100, 100);
  font = loadFont("Eureka-24.vlw");
  textFont(font);
  stroke(255);
  fill(0);
}

void draw() {
  background(204);
  float cursorPosition = textWidth(letters);
  line(cursorPosition, 0, cursorPosition, 100);
  text(letters, 0, 50);
}

void keyPressed() {
  if (key == BACKSPACE) { // Backspace
    if (letters.length() > 0) {
      letters = letters.substring(0, letters.length()-1);
    }
  } else if (textWidth(letters+key) < width){
    letters = letters+key;
  }
}