// LCD1602 to Arduino Uno connection example

#include <LiquidCrystal.h>

LiquidCrystal lcd(12, 11, 10, 9, 8, 7);

String 
storedMsgTop = "THIS IS TOP MESSAGE!",
storedMsgBtm = "THIS IS BOTTOM MESSAGE!";

String* 
rows[2] = { &storedMsgTop, &storedMsgBtm };

void printMsg() {
  byte 
  l,
  r_len[2] = { rows[0]->length(), rows[1]->length() },
  maxP = ((r_len[0] >= r_len[1] ) ? r_len[0] : r_len[1]) ;
  
  Serial.print("topMsg Len: ");Serial.println(r_len[0]);
  Serial.print("btmMsg Len: ");Serial.println(r_len[1]);
  Serial.print("max scrollLen: ");Serial.println(maxP);

  lcd.clear();

  for (l = 0; l < 2; l++) 
    lcd.setCursor(0,l), lcd.print( rows[l]->substring(0,16));
  
  delay(1000);

  if (maxP > 16) {
    for (byte p = 0; p <= (maxP-16); p++) {
      for (l = 0; l < 2; l++) {
        if ((p + 16) <= r_len[l]) {
          lcd.setCursor(0, l); 
          lcd.print(rows[l]->substring(p, r_len[l]));
        }
      }
      delay(100);
    }
  }

  delay(1000);

/*
  // BOTH LINES (SUBSTRINGS):
  if (maxP > 16) {
    for (byte p = 0; p <= (maxP-16); p++) {
      Serial.println(p); //Serial.print("  ");
      for (l = 0; l < 2; l++) {
        Serial.print("  ");Serial.println(l); Serial.print("    ");
        Serial.print("pos: "),Serial.print((p + 16)), Serial.print("/"),Serial.println(r_len[l]);Serial.print("    ");
        if ((p + 16) <= r_len[l]) {
          //Serial.print("  LINE "), Serial.print(l), 
          
          Serial.println(rows[l]->substring(p, r_len[l]));
        }
      }
      delay(1000);
    }
  }

*/

/*
  // SINGLE LINE:
  if (maxP > 16) {
    for (byte p = 0; p <= (maxP-16); p++) {
      lcd.setCursor(0, 0);
      // Print substring:
      //lcd.print(rows[0]->substring(p, r_len[0]));

      // print each char:
      for (int i = p; i < r_len[0]; i++) {
        char c = (*rows[0])[i];
        //lcd.setCursor(0, 0);
        lcd.print((*rows[0])[i]);
        Serial.print(c);
      }
      delay(1000);
    }
  }
*/

/*
// BOTH LINES
  if (maxP > 16) {
    for (byte p = 0; p < (maxP-16); p++) {
      Serial.print("p:"),Serial.println(p);
      for (l = 0; l < 2; l++) {
        if (r_len[l] > 16) {
          lcd.setCursor(0, l);
          
          char Char = ((p < r_len[0]) ? (*rows[0])[p] : char(" "));
          //Serial.print("c:"), Serial.println(c);
          lcd.print(Char);
          delay(1000);
        }
      }
    }
  }
  */



  /*
  if (maxP > 16) {
    for (byte p = 0; p < maxP; p++) {
      lcd.setCursor(0,0), lcd.print((p < r_len[0]) ? (*rows[0])[p] : " ");  
      lcd.setCursor(0,1), lcd.print((p < r_len[1]) ? (*rows[1])[p] : " "); 
    }    
  }
  */
}
/*
void scrollMsg(byte row, byte start, byte startChar) {
  lcd.setCursor(start, 0);
  for (byte c = startChar; c <= startChar + 15; c++) 
    lcd.print((c < topMsgLength) ? topMsg[c] : char(" ")); 
  delay_func(scrollDelay);
}
*/
void setup() {
  Serial.begin(9600);
  Serial.println("READY!");
  lcd.begin(16, 2);
  lcd.print("Hello World!");
  delay(1000);
}

void loop() {
    printMsg();
}