/*
長篇文之展示
ILI9341  規格:240 × 320 (TFT)
寬：240/8=30字，高：320/8=40字
中文字佔2BYTES
*/
#include "SPI.h"
#include "Adafruit_GFX.h"
#include "Adafruit_ILI9341.h"
#include "U8g2_for_Adafruit_GFX.h"

#define TFT_DC 21
#define TFT_CS 22

Adafruit_ILI9341 display = Adafruit_ILI9341(TFT_CS, TFT_DC);

U8G2_FOR_ADAFRUIT_GFX u8g2;

#define FONT u8g2_font_wqy16_t_gb2312b

const char c_str[] = 
 
"《桃花庵歌》 唐寅\n\n"
"桃花塢里桃花庵，\n"
"桃花庵下桃花仙。\n"
"桃花仙人種桃樹，\n"
"又摘桃花換酒錢。\n"
"酒醒只在花前坐，\n"
"酒醉還來花下眠。\n"
"半醉半醒日復日，\n"
"花落花開年復年。\n"
"但愿老死花酒間，\n"
"不愿鞠躬車馬前。\n"
"車塵馬足顯者事，\n"
"酒盞花枝隱士緣。\n"
"若將顯者比隱士，\n"
"一在平地一在天。\n"
"若將花酒比車馬，\n"
"彼何碌碌我何閑。\n"
"世人笑我太瘋癲，\n"
"我笑他人看不穿。\n"
"不見五陵豪杰墓，\n"
"無花無酒鋤作田。\n";



char buf[48];      //每行最多8個字，每字2BYTE 
 
uint8_t total_lines;    //總行數
uint8_t line_cnt;       //行計數器
uint8_t start_line=0;     //開始的行數
uint8_t total_page;     //總共要顯示的頁數
uint16_t height=display.height();        // height of the monitor
uint16_t width=display.width();

  

//計算唐詩的總列數，依每列最後的\n統計
uint8_t u8x8_GetStringLineCnt(const char *str)
{
  char e;
  uint8_t line_cnt = 1;
  if ( str == NULL )
    return 0;
  for(;;)
  {
    e = *str;
    if ( e == '\0' )
      break;
    str++;
    if ( e == '\n' )
      line_cnt++;
  }
  return line_cnt;
}
/* copy until first '\n' or '\0' in str */
/* Important: There is no string overflow check, ensure */
/* that the destination buffer is large enough */
void u8x8_CopyStringLine(char *dest, uint8_t line_idx, const char *str)
{
  if ( dest == NULL )
    return;
  str = u8x8_GetStringLineStart( line_idx, str );
  if ( str != NULL )
  {
    for(;;)
    {
      if ( *str == '\n' || *str == '\0' )
  break;
      *dest = *str;
      dest++;
      str++;
    }
  }
  *dest = '\0';
}


void setup() {
  display.begin();
  display.setRotation(0);
  display.fillScreen(ILI9341_BLACK);
  u8g2.begin(display);                 // connect u8g2 procedures to Adafruit GFX

  u8g2.setFont(FONT);
  u8g2.setForegroundColor(ILI9341_YELLOW);      // apply Adafruit GFX color
  
  //計算長文的總行數
  total_lines = u8x8_GetStringLineCnt(c_str);
  total_page=total_lines/40;  //每頁最多顯示40行
  
}

void loop() {  

 for(int p=0; p<total_page ;p++){
    display.fillRect(0, 0, 319, 239, ILI9341_BLACK);
    u8g2.setForegroundColor(ILI9341_WHITE);  
    line_cnt=p*40;
    for( int i = line_cnt; i <line_cnt+ 40; i++ )
    {
     /* copy a line of the text to the local buffer */
     u8x8_CopyStringLine(buf, line_cnt, c_str);    
      u8g2.drawUTF8(0, i%40, buf);
    }  
    delay(2000);
  }
  
}

const char *u8x8_GetStringLineStart(uint8_t line_idx, const char *str )
{
  char e;
  uint8_t line_cnt = 1;
  
  if ( line_idx == 0 )
    return str;

  for(;;)
  {
    e = *str;
    if ( e == '\0' )
      break;
    str++;
    if ( e == '\n' )
    {
      if ( line_cnt == line_idx )
  return str;
      line_cnt++;
    }
  }
  return NULL;  /* line not found */
}