text: /**
   * Lightweight Status Screen for the RepRapDiscount Full
   * Graphics Smart Controller (ST7920-based 128x64 LCD)
   *
   * (c) 2017 Aleph Objects, Inc.
   *
   * The code in this page is free software: you can
   * redistribute it and/or modify it under the terms of the GNU
   * General Public License (GNU GPL) as published by the Free Software
   * Foundation, either version 3 of the License, or (at your option)
   * any later version.  The code is distributed WITHOUT ANY WARRANTY;
   * without even the implied warranty of MERCHANTABILITY or FITNESS
   * FOR A PARTICULAR PURPOSE.  See the GNU GPL for more details.
   *
   */
  
  /**
   * Implementation of a Status Screen for the RepRapDiscount
   * Full Graphics Smart Controller using native ST7920 commands
   * instead of U8Glib.
   *
   * This alternative Status Screen makes use of the built-in character
   * generation capabilities of the ST7920 to update the Status Screen
   * with less SPI traffic and CPU use. In particular:
   *
   *  - The fan and bed animations are handled using custom characters
   *    that are stored in CGRAM. This allows for the animation to be
   *    updated by writing a single character to the text-buffer (DDRAM).
   *
   *  - All the information in the Status Screen is text that is written
   *    to DDRAM, so the work of generating the bitmaps is offloaded to
   *    the ST7920 rather than being render by U8Glib on the MCU.
   *
   *  - The graphics buffer (GDRAM) is only used for static graphics
   *    elements (nozzle and feedrate bitmaps) and for the progress
   *    bar, so updates are sporadic.
   */
  
  //
  // status_screen_lite_ST7920.cpp
  // Lightweight Status Screen for Graphical Display
  //
  
  #include "../../inc/MarlinConfigPre.h"
  
  #if ENABLED(LIGHTWEIGHT_UI)
  
  #include "status_screen_lite_ST7920.h"
  
  #include "../ultralcd.h"
  #include "../fontutils.h"
  #include "../lcdprint.h"
  #include "../../libs/duration_t.h"
  #include "../../module/motion.h"
  #include "../../module/printcounter.h"
  #include "../../module/temperature.h"
  
  #if ENABLED(SDSUPPORT)
    #include "../../sd/cardreader.h"
  #endif
  
  #if ENABLED(LCD_SHOW_E_TOTAL)
    #include "../../MarlinCore.h" // for printingIsActive
  #endif
  
  #define TEXT_MODE_LCD_WIDTH 16
  
  #define BUFFER_WIDTH   256
  #define BUFFER_HEIGHT  32
  
  #define DDRAM_LINE_1   0x00
  #define DDRAM_LINE_2   0x10
  #define DDRAM_LINE_3   0x08
  #define DDRAM_LINE_4   0x18
  
  ST7920_Lite_Status_Screen::st7920_state_t ST7920_Lite_Status_Screen::current_bits;
  
  void ST7920_Lite_Status_Screen::cmd(const uint8_t cmd) {
    if (!current_bits.synced || !current_bits.cmd) {
      current_bits.synced = true;
      current_bits.cmd    = true;
      sync_cmd();
    }
    write_byte(cmd);
  }
  
  void ST7920_Lite_Status_Screen::begin_data() {
    if (!current_bits.synced || current_bits.cmd) {
      current_bits.synced = true;
      current_bits.cmd    = false;
      sync_dat();
    }
  }
  
  void ST7920_Lite_Status_Screen::write_str(const char *str) {
    while (*str) write_byte(*str++);
  }
  
  void ST7920_Lite_Status_Screen::write_str(const char *str, uint8_t len) {
    while (*str && len--) write_byte(*str++);
  }
  
  void ST7920_Lite_Status_Screen::write_str_P(PGM_P const str) {
    PGM_P p_str = (PGM_P)str;
    while (char c = pgm_read_byte(p_str++)) write_byte(c);
  }
  
  void ST7920_Lite_Status_Screen::write_number(const int16_t value, const uint8_t digits/*=3*/) {
    char str[7];
    PGM_P fmt;
    switch (digits) {
      case 6: fmt = PSTR("%6d"); break;
      case 5: fmt = PSTR("%5d"); break;
      case 4: fmt = PSTR("%4d"); break;
      case 3: fmt = PSTR("%3d"); break;
      case 2: fmt = PSTR("%2d"); break;
      case 1: fmt = PSTR("%1d"); break;
      default: return;
    }
    sprintf_P(str, fmt, value);
    write_str(str);
  }
  
  void ST7920_Lite_Status_Screen::display_status(const bool display_on, const bool cursor_on, const bool blink_on) {
    extended_function_set(false);
    cmd(0b00001000 |
      (display_on ? 0b0100 : 0) |
      (cursor_on  ? 0b0010 : 0) |
      (blink_on   ? 0b0001 : 0)
    );
  }
  
  // Sets the extended and graphics bits simultaneously, regardless of
  // the current state. This is a helper function for extended_function_set()
  // and graphics()
  void ST7920_Lite_Status_Screen::_extended_function_set(const bool extended, const bool graphics) {
    cmd(  0b00100000 |
      (extended   ? 0b00000100 : 0) |
      (graphics   ? 0b00000010 : 0)
    );
    current_bits.extended = extended;
    current_bits.graphics = graphics;
  }
  
  void ST7920_Lite_Status_Screen::extended_function_set(const bool extended) {
    if (extended != current_bits.extended)
      _extended_function_set(extended, current_bits.graphics);
  }
  
  void ST7920_Lite_Status_Screen::graphics(const bool graphics) {
    if (graphics != current_bits.graphics)
      _extended_function_set(current_bits.extended, graphics);
  }
  
  void ST7920_Lite_Status_Screen::entry_mode_select(const bool ac_increase, const bool shift) {
    extended_function_set(false);
    cmd(0b00000100 |
      (ac_increase ? 0b00000010 : 0) |
      (shift       ? 0b00000001 : 0)
    );
  }
  
  // Sets the sa bit regardless of the current state. This is a helper
  // function for scroll_or_addr_select()
  void ST7920_Lite_Status_Screen::_scroll_or_addr_select(const bool sa) {
    extended_function_set(true);
    cmd(0b00000010 | (sa ? 0b00000001 : 0));
    current_bits.sa = sa;
  }
  
  void ST7920_Lite_Status_Screen::scroll_or_addr_select(const bool sa) {
    if (sa != current_bits.sa)
      _scroll_or_addr_select(sa);
  }
  
  void ST7920_Lite_Status_Screen::set_ddram_address(const uint8_t addr) {
    extended_function_set(false);
    cmd(0b10000000 | (addr & 0b00111111));
  }
  
  void ST7920_Lite_Status_Screen::set_cgram_address(const uint8_t addr) {
    extended_function_set(false);
    cmd(0b01000000 | (addr & 0b00111111));
  }
  
  void ST7920_Lite_Status_Screen::set_gdram_address(const uint8_t x, const uint8_t y) {
    extended_function_set(true);
    cmd(0b10000000 | (y & 0b01111111));
    cmd(0b10000000 | (x & 0b00001111));
  }
  
  void ST7920_Lite_Status_Screen::clear() {
    extended_function_set(false);
    cmd(0x00000001);
    delay(15);                 //delay for CGRAM clear
  }
  
  void ST7920_Lite_Status_Screen::home() {
    extended_function_set(false);
    cmd(0x00000010);
  }
  
  /* This fills the entire text buffer with spaces */
  void ST7920_Lite_Status_Screen::clear_ddram() {
    set_ddram_address(DDRAM_LINE_1);
    begin_data();
    for (uint8_t i = 64; i--;) write_byte(' ');
  }
  
  /* This fills the entire graphics buffer with zeros */
  void ST7920_Lite_Status_Screen::clear_gdram() {
    LOOP_L_N(y, BUFFER_HEIGHT) {
      set_gdram_address(0, y);
      begin_data();
      for (uint8_t i = (BUFFER_WIDTH) / 16; i--;) write_word(0);
    }
  }
  
  void ST7920_Lite_Status_Screen::load_cgram_icon(const uint16_t addr, const void *data) {
    const uint16_t *p_word = (const uint16_t *)data;
    set_cgram_address(addr);
    begin_data();
    for (uint8_t i = 16; i--;)
      write_word(pgm_read_word(p_word++));
  }
  
  /**
   * Draw an icon in GDRAM. Position specified in DDRAM
   * coordinates. i.e., X from 1 to 8, Y from 1 to 4.
   */
  void ST7920_Lite_Status_Screen::draw_gdram_icon(uint8_t x, uint8_t y, const void *data) {
    const uint16_t *p_word = (const uint16_t *)data;
    // Handle display folding
    if (y > 1) y -= 2, x += 8;
    for (int i = 0; i < 16; i++) {
      set_gdram_address(x, i + y * 16);
      begin_data();
      write_word(pgm_read_word(p_word++));
    }
  }
  
  /************************** ICON DEFINITIONS *************************************/
  
  #define CGRAM_ICON_1_ADDR 0x00
  #define CGRAM_ICON_2_ADDR 0x10
  #define CGRAM_ICON_3_ADDR 0x20
  #define CGRAM_ICON_4_ADDR 0x30
  
  #define CGRAM_ICON_1_WORD 0x00
  #define CGRAM_ICON_2_WORD 0x02
  #define CGRAM_ICON_3_WORD 0x04
  #define CGRAM_ICON_4_WORD 0x06
  
  const uint8_t degree_symbol_y_top = 1;
  PROGMEM const uint8_t degree_symbol[] = {
    0b00110000,
    0b01001000,
    0b01001000,
    0b00110000,
  };
  
  const uint16_t nozzle_icon[] PROGMEM = {
    0b0000000000000000,
    0b0000000000000000,
    0b0000111111110000,
    0b0001111111111000,
    0b0001111111111000,
    0b0001111111111000,
    0b0000111111110000,
    0b0000111111110000,
    0b0001111111111000,
    0b0001111111111000,
    0b0001111111111000,
    0b0000011111100000,
    0b0000001111000000,
    0b0000000110000000,
    0b0000000000000000,
    0b0000000000000000
  };
  
  const uint16_t bed_icon[] PROGMEM = {
    0b0000000000000000,
    0b0000000000000000,
    0b0000000000000000,
    0b0000000000000000,
    0b0000000000000000,
    0b0000000000000000,
    0b0000000000000000,
    0b0000000000000000,
    0b0000000000000000,
    0b0000000000000000,
    0b0000000000000000,
    0b0111111111111110,
    0b0111111111111110,
    0b0110000000000110,
    0b0000000000000000,
    0b0000000000000000
  };
  
  const uint16_t heat1_icon[] PROGMEM = {
    0b0000000000000000,
    0b0010001000100000,
    0b0001000100010000,
    0b0000100010001000,
    0b0000100010001000,
    0b0001000100010000,
    0b0010001000100000,
    0b0010001000100000,
    0b0001000100010000,
    0b0000100010001000,
    0b0000000000000000,
    0b0000000000000000,
    0b0000000000000000,
    0b0000000000000000,
    0b0000000000000000,
    0b0000000000000000
  };
  
  const uint16_t heat2_icon[] PROGMEM = {
    0b0000000000000000,
    0b0000100010001000,
    0b0000100010001000,
    0b0001000100010000,
    0b0010001000100000,
    0b0010001000100000,
    0b0001000100010000,
    0b0000100010001000,
    0b0000100010001000,
    0b0001000100010000,
    0b0000000000000000,
    0b0000000000000000,
    0b0000000000000000,
    0b0000000000000000,
    0b0000000000000000,
    0b0000000000000000
  };
  
  const uint16_t fan1_icon[] PROGMEM = {
    0b0000000000000000,
    0b0111111111111110,
    0b0111000000001110,
    0b0110001111000110,
    0b0100001111000010,
    0b0100000110000010,
    0b0101100000011010,
    0b0101110110111010,
    0b0101100000011010,
    0b0100000110000010,
    0b0100001111000010,
    0b0110001111000110,
    0b0111000000001110,
    0b0111111111111110,
    0b0000000000000000,
    0b0000000000000000
  };
  
  const uint16_t fan2_icon[] PROGMEM = {
    0b0000000000000000,
    0b0111111111111110,
    0b0111000000001110,
    0b0110010000100110,
    0b0100111001110010,
    0b0101111001111010,
    0b0100110000110010,
    0b0100000110000010,
    0b0100110000110010,
    0b0101111001111010,
    0b0100111001110010,
    0b0110010000100110,
    0b0111000000001110,
    0b0111111111111110,
    0b0000000000000000,
    0b0000000000000000
  };
  
  const uint16_t feedrate_icon[] PROGMEM = {
    0b0000000000000000,
    0b0111111000000000,
    0b0110000000000000,
    0b0110000000000000,
    0b0110000000000000,
    0b0111111011111000,
    0b0110000011001100,
    0b0110000011001100,
    0b0110000011001100,
    0b0110000011111000,
    0b0000000011001100,
    0b0000000011001100,
    0b0000000011001100,
    0b0000000011001100,
    0b0000000000000000,
    0b0000000000000000
  };
  
  /************************** MAIN SCREEN *************************************/
  
  /**
   * The ST7920 has no degree character, so draw it to GDRAM.
   * This function takes character position xy
   * i.e., x is [0-15], while the y position is [0-3]
   */
  void ST7920_Lite_Status_Screen::draw_degree_symbol(uint8_t x, uint8_t y, const bool draw) {
    const uint8_t *p_bytes = degree_symbol;
      // Handle display folding
      if (y > 1) y -= 2, x += 16;
      const bool    oddChar = x & 1;
      const uint8_t x_word  = x >> 1,
                    y_top   = degree_symbol_y_top,
                    y_bot   = y_top + COUNT(degree_symbol);
      LOOP_S_L_N(i, y_top, y_bot) {
        uint8_t byte = pgm_read_byte(p_bytes++);
        set_gdram_address(x_word, i + y * 16);
        begin_data();
        if (draw) {
          write_byte(oddChar ? 0x00 : byte);
          write_byte(oddChar ? byte : 0x00);
        }
        else
          write_word(0x0000);
      }
  }
  
  void ST7920_Lite_Status_Screen::draw_static_elements() {
    scroll_or_addr_select(0);
  
    // Load the animated bed and fan icons
    load_cgram_icon(CGRAM_ICON_1_ADDR, heat1_icon);
    load_cgram_icon(CGRAM_ICON_2_ADDR, heat2_icon);
    load_cgram_icon(CGRAM_ICON_3_ADDR, fan1_icon);
    load_cgram_icon(CGRAM_ICON_4_ADDR, fan2_icon);
  
    // Draw the static icons in GDRAM
    draw_gdram_icon(0, 0, nozzle_icon);
    #if HAS_MULTI_HOTEND
      draw_gdram_icon(0, 1, nozzle_icon);
      draw_gdram_icon(0, 2, bed_icon);
    #else
      draw_gdram_icon(0, 1, bed_icon);
    #endif
    draw_gdram_icon(5, 1, feedrate_icon);
  
    // Draw the initial fan icon
    draw_fan_icon(false);
  }
  
  /**
   * Although this is undocumented, the ST7920 allows the character
   * data buffer (DDRAM) to be used in conjunction with the graphics
   * bitmap buffer (CGRAM). The contents of the graphics buffer is
   * XORed with the data from the character generator. This allows
   * us to make the progess bar out of graphical data (the bar) and
   * text data (the percentage).
   */
  void ST7920_Lite_Status_Screen::draw_progress_bar(const uint8_t value) {
    #if HOTENDS == 1
      // If we have only one extruder, draw a long progress bar on the third line
      constexpr uint8_t top     = 1,         // Top in pixels
                        bottom  = 13,        // Bottom in pixels
                        left    = 12,        // Left edge, in 16-bit words
                        width   = 4;         // Width of progress bar, in 16-bit words
    #else
      constexpr uint8_t top     = 16 + 1,
                        bottom  = 16 + 13,
                        left    = 5,
                        width   = 3;
    #endif
    const uint8_t char_pcnt  = 100 / width; // How many percent does each 16-bit word represent?
  
    // Draw the progress bar as a bitmap in CGRAM
    LOOP_S_LE_N(y, top, bottom) {
      set_gdram_address(left, y);
      begin_data();
      LOOP_L_N(x, width) {
        uint16_t gfx_word = 0x0000;
        if ((x + 1) * char_pcnt <= value)
          gfx_word = 0xFFFF;                                              // Draw completely filled bytes
        else if ((x * char_pcnt) < value)
          gfx_word = int(0x8000) >> (value % char_pcnt) * 16 / char_pcnt; // Draw partially filled bytes
  
        // Draw the frame around the progress bar
        if (y == top || y == bottom)
          gfx_word = 0xFFFF;        // Draw top/bottom border
        else if (x == width - 1)
          gfx_word |= 0x0001;       // Draw right border
        else if (x == 0)
          gfx_word |= 0x8000;       // Draw left border
        write_word(gfx_word);
      }
    }
  
    // Draw the percentage as text in DDRAM
    #if HOTENDS == 1
      set_ddram_address(DDRAM_LINE_3 + 4);
      begin_data();
      write_byte(' ');
    #else
      set_ddram_address(DDRAM_LINE_2 + left);
      begin_data();
    #endif
  
    // Draw centered
    if (value > 9) {
      write_number(value, 4);
      write_str_P(PSTR("% "));
    }
    else {
      write_number(value, 3);
      write_str_P(PSTR("%  "));
    }
  }
  
  void ST7920_Lite_Status_Screen::draw_fan_icon(const bool whichIcon) {
    set_ddram_address(DDRAM_LINE_1 + 5);
    begin_data();
    write_word(whichIcon ? CGRAM_ICON_3_WORD : CGRAM_ICON_4_WORD);
  }
  
  void ST7920_Lite_Status_Screen::draw_heat_icon(const bool whichIcon, const bool heating) {
    set_ddram_address(
      #if HOTENDS == 1
        DDRAM_LINE_2
      #else
        DDRAM_LINE_3
      #endif
    );
    begin_data();
    if (heating)
      write_word(whichIcon ? CGRAM_ICON_1_WORD : CGRAM_ICON_2_WORD);
    else {
      write_byte(' ');
      write_byte(' ');
    }
  }
  
  #define FAR(a,b) (((a > b) ? (a-b) : (b-a)) > 2)
  
  static struct {
    bool E1_show_target  : 1;
    bool E2_show_target  : 1;
    TERN_(HAS_HEATED_BED, bool bed_show_target : 1);
  } display_state = {
    true, true, TERN_(HAS_HEATED_BED, true)
  };
  
  void ST7920_Lite_Status_Screen::draw_temps(uint8_t line, const int16_t temp, const int16_t target, bool showTarget, bool targetStateChange) {
    switch (line) {
      case 0: set_ddram_address(DDRAM_LINE_1 + 1); break;
      case 1: set_ddram_address(DDRAM_LINE_2 + 1); break;
      case 2: set_ddram_address(DDRAM_LINE_3 + 1); break;
      case 3: set_ddram_address(DDRAM_LINE_3 + 1); break;
    }
    begin_data();
    write_number(temp);
  
    if (showTarget) {
      write_byte('\x1A');
      write_number(target);
    };
  
    if (targetStateChange) {
      if (!showTarget) write_str_P(PSTR("    "));
      draw_degree_symbol(5, line, !showTarget);
      draw_degree_symbol(9, line,  showTarget);
    }
  }
  
  void ST7920_Lite_Status_Screen::draw_extruder_1_temp(const int16_t temp, const int16_t target, bool forceUpdate) {
    const bool show_target = target && FAR(temp, target);
    draw_temps(0, temp, target, show_target, display_state.E1_show_target != show_target || forceUpdate);
    display_state.E1_show_target = show_target;
  }
  
  void ST7920_Lite_Status_Screen::draw_extruder_2_temp(const int16_t temp, const int16_t target, bool forceUpdate) {
    const bool show_target = target && FAR(temp, target);
    draw_temps(1, temp, target, show_target, display_state.E2_show_target != show_target || forceUpdate);
    display_state.E2_show_target = show_target;
  }
  
  #if HAS_HEATED_BED
    void ST7920_Lite_Status_Screen::draw_bed_temp(const int16_t temp, const int16_t target, bool forceUpdate) {
      const bool show_target = target && FAR(temp, target);
      draw_temps(TERN(HAS_MULTI_HOTEND, 2, 1), temp, target, show_target, display_state.bed_show_target != show_target || forceUpdate);
      display_state.bed_show_target = show_target;
    }
  #endif
  
  void ST7920_Lite_Status_Screen::draw_fan_speed(const uint8_t value) {
    set_ddram_address(DDRAM_LINE_1 + 6);
    begin_data();
    write_number(value, 3);
    write_byte('%');
  }
  
  void ST7920_Lite_Status_Screen::draw_print_time(const duration_t &elapsed) {
    #if HOTENDS == 1
      set_ddram_address(DDRAM_LINE_3);
    #else
      set_ddram_address(DDRAM_LINE_3 + 5);
    #endif
    char str[7];
    str[elapsed.toDigital(str)] = ' ';
    begin_data();
    write_str(str, 6);
  }
  
  void ST7920_Lite_Status_Screen::draw_feedrate_percentage(const uint16_t percentage) {
    // We only have enough room for the feedrate when
    // we have one extruder
    #if HOTENDS == 1
      set_ddram_address(DDRAM_LINE_2 + 6);
      begin_data();
      write_number(percentage, 3);
      write_byte('%');
    #else
      UNUSED(percentage);
    #endif
  }
  
  void ST7920_Lite_Status_Screen::draw_status_message() {
    const char *str = ui.status_message;
  
    set_ddram_address(DDRAM_LINE_4);
    begin_data();
    #if ENABLED(STATUS_MESSAGE_SCROLLING)
      uint8_t slen = utf8_strlen(str);
  
      if (slen <= TEXT_MODE_LCD_WIDTH) {
        // String fits the LCD, so just print it
        write_str(str);
        while (slen < TEXT_MODE_LCD_WIDTH) { write_byte(' '); ++slen; }
      }
      else {
        // String is larger than the available space in screen.
  
        // Get a pointer to the next valid UTF8 character
        // and the string remaining length
        uint8_t rlen;
        const char *stat = ui.status_and_len(rlen);
        write_str(stat, TEXT_MODE_LCD_WIDTH);
  
        // If the remaining string doesn't completely fill the screen
        if (rlen < TEXT_MODE_LCD_WIDTH) {
          write_byte('.');                        // Always at 1+ spaces left, draw a dot
          uint8_t chars = TEXT_MODE_LCD_WIDTH - rlen;       // Amount of space left in characters
          if (--chars) {                          // Draw a second dot if there's space
            write_byte('.');
            if (--chars) write_str(str, chars);   // Print a second copy of the message
          }
        }
        ui.advance_status_scroll();
      }
  
    #else
  
      uint8_t slen = utf8_strlen(str);
      write_str(str, TEXT_MODE_LCD_WIDTH);
      for (; slen < TEXT_MODE_LCD_WIDTH; ++slen) write_byte(' ');
  
    #endif
  }
  
  void ST7920_Lite_Status_Screen::draw_position(const xyze_pos_t &pos, const bool position_known) {
    char str[7];
    set_ddram_address(DDRAM_LINE_4);
    begin_data();
  
    // If position is unknown, flash the labels.
    const unsigned char alt_label = position_known ? 0 : (ui.get_blink() ? ' ' : 0);
  
    if (TERN1(LCD_SHOW_E_TOTAL, !printingIsActive())) {
      write_byte(alt_label ? alt_label : 'X');
      write_str(dtostrf(pos.x, -4, 0, str), 4);
  
      write_byte(alt_label ? alt_label : 'Y');
      write_str(dtostrf(pos.y, -4, 0, str), 4);
    }
    else {
      #if ENABLED(LCD_SHOW_E_TOTAL)
        char tmp[15];
        const uint8_t escale = e_move_accumulator >= 100000.0f ? 10 : 1; // After 100m switch to cm
        sprintf_P(tmp, PSTR("E%-7ld%cm "), uint32_t(_MAX(e_move_accumulator, 0.0f)) / escale, escale == 10 ? 'c' : 'm'); // 1234567mm
        write_str(tmp);
      #endif
    }
  
    write_byte(alt_label ? alt_label : 'Z');
    write_str(dtostrf(pos.z, -5, 1, str), 5);
  }
  
  bool ST7920_Lite_Status_Screen::indicators_changed() {
    // We only add the target temperatures to the checksum
    // because the actual temps fluctuate so by updating
    // them only during blinks we gain a bit of stability.
    const bool       blink             = ui.get_blink();
    const uint16_t   feedrate_perc     = feedrate_percentage;
    const uint16_t   fs                = thermalManager.scaledFanSpeed(0);
    const int16_t    extruder_1_target = thermalManager.degTargetHotend(0);
    #if HAS_MULTI_HOTEND
      const int16_t  extruder_2_target = thermalManager.degTargetHotend(1);
    #endif
    #if HAS_HEATED_BED
      const int16_t  bed_target        = thermalManager.degTargetBed();
    #endif
    static uint16_t last_checksum = 0;
    const uint16_t checksum = blink ^ feedrate_perc ^ fs ^ extruder_1_target
      ^ TERN0(HAS_MULTI_HOTEND, extruder_2_target)
      ^ TERN0(HAS_HEATED_BED, bed_target);
    if (last_checksum == checksum) return false;
    last_checksum = checksum;
    return true;
  }
  
  void ST7920_Lite_Status_Screen::update_indicators(const bool forceUpdate) {
    if (forceUpdate || indicators_changed()) {
      const bool       blink             = ui.get_blink();
      const duration_t elapsed           = print_job_timer.duration();
      const uint16_t   feedrate_perc     = feedrate_percentage;
      const int16_t    extruder_1_temp   = thermalManager.degHotend(0),
                       extruder_1_target = thermalManager.degTargetHotend(0);
      #if HAS_MULTI_HOTEND
        const int16_t  extruder_2_temp   = thermalManager.degHotend(1),
                       extruder_2_target = thermalManager.degTargetHotend(1);
      #endif
      #if HAS_HEATED_BED
        const int16_t  bed_temp          = thermalManager.degBed(),
                       bed_target        = thermalManager.degTargetBed();
      #endif
  
      draw_extruder_1_temp(extruder_1_temp, extruder_1_target, forceUpdate);
      TERN_(HAS_MULTI_HOTEND, draw_extruder_2_temp(extruder_2_temp, extruder_2_target, forceUpdate));
      TERN_(HAS_HEATED_BED, draw_bed_temp(bed_temp, bed_target, forceUpdate));
  
      uint16_t spd = thermalManager.fan_speed[0];
  
      #if ENABLED(ADAPTIVE_FAN_SLOWING)
        if (!blink && thermalManager.fan_speed_scaler[0] < 128)
          spd = thermalManager.scaledFanSpeed(0, spd);
      #endif
  
      draw_fan_speed(thermalManager.fanPercent(spd));
      draw_print_time(elapsed);
      draw_feedrate_percentage(feedrate_perc);
  
      // Update the fan and bed animations
      if (spd) draw_fan_icon(blink);
      TERN_(HAS_HEATED_BED, draw_heat_icon(bed_target > 0 && blink, bed_target > 0));
    }
  }
  
  bool ST7920_Lite_Status_Screen::position_changed() {
    const xyz_pos_t pos = current_position;
    const uint8_t checksum = uint8_t(pos.x) ^ uint8_t(pos.y) ^ uint8_t(pos.z);
    static uint8_t last_checksum = 0, changed = last_checksum != checksum;
    if (changed) last_checksum = checksum;
    return changed;
  }
  
  bool ST7920_Lite_Status_Screen::status_changed() {
    uint8_t checksum = 0;
    for (const char *p = ui.status_message; *p; p++) checksum ^= *p;
    static uint8_t last_checksum = 0;
    bool changed = last_checksum != checksum;
    if (changed) last_checksum = checksum;
    return changed;
  }
  
  bool ST7920_Lite_Status_Screen::blink_changed() {
    static uint8_t last_blink = 0;
    const bool blink = ui.get_blink(), changed = last_blink != blink;
    if (changed) last_blink = blink;
    return changed;
  }
  
  #ifndef STATUS_EXPIRE_SECONDS
    #define STATUS_EXPIRE_SECONDS 20
  #endif
  
  void ST7920_Lite_Status_Screen::update_status_or_position(bool forceUpdate) {
  
    #if STATUS_EXPIRE_SECONDS
      static uint8_t countdown = 0;
    #endif
  
    /**
     * There's only enough room for either the status message or the position,
     * so draw one or the other. When the status message changes, show it for
     * a few seconds, then return to the position display once the head moves.
     *
     *  countdown > 1  -- Show status
     *  countdown = 1  -- Show status, until movement
     *  countdown = 0  -- Show position
     *
     * If STATUS_EXPIRE_SECONDS is zero, only the status is shown.
     */
    if (forceUpdate || status_changed()) {
      TERN_(STATUS_MESSAGE_SCROLLING, ui.status_scroll_offset = 0);
      #if STATUS_EXPIRE_SECONDS
        countdown = ui.status_message[0] ? STATUS_EXPIRE_SECONDS : 0;
      #endif
      draw_status_message();
      blink_changed(); // Clear changed flag
    }
    #if !STATUS_EXPIRE_SECONDS
      else if (TERN0(STATUS_MESSAGE_SCROLLING, blink_changed()))
        draw_status_message();
    #else
      else if (blink_changed()) {
        if (countdown > 1) {
          countdown--;
          TERN_(STATUS_MESSAGE_SCROLLING, draw_status_message());
        }
        else if (countdown > 0) {
          if (position_changed()) {
            countdown--;
            forceUpdate = true;
          }
          TERN_(STATUS_MESSAGE_SCROLLING, draw_status_message());
        }
      }
  
      if (countdown == 0 && (forceUpdate || position_changed()
        #if DISABLED(DISABLE_REDUCED_ACCURACY_WARNING)
          || blink_changed()
        #endif
      )) {
        draw_position(current_position, true
          #if DISABLED(DISABLE_REDUCED_ACCURACY_WARNING)
            && all_axes_known()
          #endif
        );
      }
    #endif
  }
  
  void ST7920_Lite_Status_Screen::update_progress(const bool forceUpdate) {
    #if EITHER(LCD_SET_PROGRESS_MANUALLY, SDSUPPORT)
  
      // Since the progress bar involves writing
      // quite a few bytes to GDRAM, only do this
      // when an update is actually necessary.
  
      static uint8_t last_progress = 0;
      const uint8_t progress = ui.get_progress_percent();
      if (forceUpdate || last_progress != progress) {
        last_progress = progress;
        draw_progress_bar(progress);
      }
  
    #else
  
      UNUSED(forceUpdate);
  
    #endif // LCD_SET_PROGRESS_MANUALLY || SDSUPPORT
  }
  
  void ST7920_Lite_Status_Screen::update(const bool forceUpdate) {
    cs();
    update_indicators(forceUpdate);
    update_status_or_position(forceUpdate);
    update_progress(forceUpdate);
    ncs();
  }
  
  void ST7920_Lite_Status_Screen::reset_state_from_unknown() {
    _extended_function_set(true, true); // Do it twice as only one bit
    _extended_function_set(true, true); // get set at a time.
    _scroll_or_addr_select(false);
  }
  
  void ST7920_Lite_Status_Screen::on_entry() {
    cs();
    reset_state_from_unknown();
    clear();
    clear_gdram();
    draw_static_elements();
    update(true);
    ncs();
  }
  
  void ST7920_Lite_Status_Screen::on_exit() {
    cs();
    clear();
    _extended_function_set(true, true); // Restore state to what u8g expects.
    ncs();
  }
  
  // Called prior to the KILL screen to
  // clear the screen, preventing a garbled display.
  void ST7920_Lite_Status_Screen::clear_text_buffer() {
    cs();
    reset_state_from_unknown();
    clear();
    _extended_function_set(true, true); // Restore state to what u8g expects.
    ncs();
  }
  
  void MarlinUI::draw_status_screen() {
    ST7920_Lite_Status_Screen::update(false);
  }
  
  // This method is called before each screen update and
  // fires on_entry() and on_exit() events upon entering
  // or exiting the Status Screen.
  void MarlinUI::lcd_in_status(const bool inStatus) {
    static bool lastInStatus = false;
    if (lastInStatus == inStatus) return;
    if ((lastInStatus = inStatus))
      ST7920_Lite_Status_Screen::on_entry();
    else
      ST7920_Lite_Status_Screen::on_exit();
  }
  
  #endif // LIGHTWEIGHT_UI
  