#define LCD_SCROLL_SPEED 20

struct Lcd
{
  char text[4][21];
  char scrollText[4][100];
  int scrollIndex[4];
  int scroll[4]; //0 don't scroll, count up 500 code loops and then increment scrollIndex
  bool updateLine[4];
  bool update;
};

struct Lcd lcd;

char test[] = "Main Cue List this is some text which is more than to characters long";

void setup() {
  // put your setup code here, to run once:
  Serial.begin(115200);
  Serial.println("Hello, ESP32!");

  snprintf(lcd.scrollText[0], 100, "Main Cue List this is some text which is more than to characters long");
  lcd.scroll[0] = 1;
}

void loop() {
  // put your main code here, to run repeatedly:
  delay(10); // this speeds up the simulation
  serviceLcdScroll();
}

void serviceLcdScroll()
{
  for (int i = 0; i < 4; i++)
  {
    if (lcd.scroll[i] > 0)
    {
      lcd.scroll[i]++;
    }
    if (lcd.scroll[i] == LCD_SCROLL_SPEED )
    {
      if (lcd.scrollIndex[i] < strlen(lcd.scrollText[i]) + 19) //scrollIndex runs for the length of the text + length of lcd -1
      {
        lcd.scrollIndex[i]++;
      }
      else {
        lcd.scrollIndex[i] = 0;
      }
      for (int j = 0; j < 20; j++)
      {
        int k = j + lcd.scrollIndex[i];
        if (k > strlen(lcd.scrollText[i]) + 19) //keep going until the last character is on the left most character of the screen.
        {
          k = k - strlen(lcd.scrollText[i])-19;//adjust k to put the first character on the right most character of the screen.
        }
        if (k >= 20) //fill lcd.text with part of scrollText
        {
          lcd.text[i][j] = lcd.scrollText[i][k-20];
        }
        else { //fill lcd.text with spaces
          lcd.text[i][j] = ' ';
        }
      }
      Serial.println(lcd.text[0]);
      lcd.update = 1;
      lcd.scroll[i] = 1;
    }
  }
}