// include the library
#include <LCD.h>

// =============================================
// Adjust this block of code if you have another LCD (e.g. direct connected)
#include <LiquidCrystal_I2C.h>

#define I2C_ADDR    0x3f
#define BACKLIGHT_PIN     3
#define En_pin  2
#define Rw_pin  1
#define Rs_pin  0
#define D4_pin  4
#define D5_pin  5
#define D6_pin  6
#define D7_pin  7

LiquidCrystal_I2C    lcd(I2C_ADDR, En_pin, Rw_pin, Rs_pin, D4_pin, D5_pin, D6_pin, D7_pin, BACKLIGHT_PIN, POSITIVE);
// =============================================

// it's a 16x2 LCD so...
int screenWidth = 16;
int screenHeight = 2;

int countMovement = 0;
int stringStart = 0;
int stringStop = 0;
int scrollCursor = 0;

void setup() {
  Serial.begin(9600);
  lcd.begin(screenWidth, screenHeight);
}

void loop() {

  lcd.clear();
  lcd.setCursor(0, 1);
  lcd.print("Scroll-row0");
  scroll(0, "The quick brown fox jumps over the lazy dog",200);
  delay(2000);

  lcd.clear();
  lcd.setCursor(0, 0);
  lcd.print("Scroll-row1");
  scroll(1, "This line scrolls normal (200ms delay)", 200 );
  delay(2000);


  lcd.clear();
  lcd.setCursor(0, 0);
  lcd.print("Scroll-row1");
  scroll(1, "This line scrolls fast (100ms delay)", 100 );
  delay(2000);

}

// ==========================================
void scroll(int row, String line, int speed) {
  countMovement = 0;
  stringStart = 0;
  stringStop = 0;
  scrollCursor = 0;

  // Serial.print(countMovement); Serial.print("-"); Serial.println(line.length() + 1);
  while ( ( countMovement ) < (line.length() + 2 )  )
  {
    lcd.setCursor(scrollCursor, row);
    // Serial.print("Cursor: "); Serial.print(scrollCursor); Serial.print(" "); Serial.println(row);
    lcd.print(line.substring(stringStart, stringStop));
    // Serial.println( line.substring(stringStart, stringStop) );
    delay(speed);

    if (stringStart == 0 && scrollCursor > 0) {
      // Serial.println(scrollCursor);
      scrollCursor--;
      stringStop++;
    } else if (stringStart == stringStop) {
      stringStart = stringStop = 0;
      scrollCursor = screenWidth;
    } else if (stringStop == line.length() && scrollCursor == 0) {
      stringStart++;
    } else {
      stringStart++;
      stringStop++;
    }
    countMovement++;
  }
}