/***********************************************************************
* ftermlinux.cpp - Contains the Linux terminal functions               *
*                                                                      *
* This file is part of the FINAL CUT widget toolkit                    *
*                                                                      *
* Copyright 2018-2020 Markus Gans                                      *
*                                                                      *
* FINAL CUT is free software; you can redistribute it and/or modify    *
* it under the terms of the GNU Lesser General Public License as       *
* published by the Free Software Foundation; either version 3 of       *
* the License, or (at your option) any later version.                  *
*                                                                      *
* FINAL CUT is distributed in the hope that it will be useful, but     *
* WITHOUT ANY WARRANTY; without even the implied warranty of           *
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the        *
* GNU Lesser General Public License for more details.                  *
*                                                                      *
* You should have received a copy of the GNU Lesser General Public     *
* License along with this program.  If not, see                        *
* <http://www.gnu.org/licenses/>.                                      *
***********************************************************************/

#include <vector>

#include "final/fapplication.h"
#include "final/fc.h"
#include "final/fcharmap.h"
#include "final/flog.h"
#include "final/fsystem.h"
#include "final/fterm.h"
#include "final/ftermcap.h"
#include "final/ftermdetection.h"
#include "final/ftermlinux.h"
#include "final/ftypes.h"

#if defined(__linux__)
  #include <linux/keyboard.h>  // need keyboard modifiers
  #include "../fonts/newfont.h"
  #include "../fonts/unicodemap.h"
  #include "../fonts/vgafont.h"
#endif

namespace finalcut
{

//----------------------------------------------------------------------
// class FTermLinux
//----------------------------------------------------------------------

// constructors and destructor
//----------------------------------------------------------------------
FTermLinux::~FTermLinux()  // destructor
{
#if defined(__linux__)
  if ( screen_font.data )
    delete[] screen_font.data;

  if ( screen_unicode_map.entries )
    delete[] screen_unicode_map.entries;
#endif  // defined(__linux__)
}

// public methods of FTermLinux
//----------------------------------------------------------------------
#if defined(__linux__)
fc::linuxConsoleCursorStyle FTermLinux::getCursorStyle() const
{
  // Get the current set cursor style

  return linux_console_cursor_style;
}

//----------------------------------------------------------------------
char* FTermLinux::getCursorStyleString()
{
  // Gets the current cursor style string of the Linux console

  static char buf[16]{};
  std::fill (std::begin(buf), std::end(buf), '\0');
  std::snprintf (buf, sizeof(buf), CSI "?%dc", getCursorStyle());
  return buf;
}

//----------------------------------------------------------------------
bool FTermLinux::setCursorStyle (fc::linuxConsoleCursorStyle style)
{
  // Set cursor style in linux console

  if ( ! fterm_data )
    fterm_data = FTerm::getFTermData();

  if ( ! FTerm::isLinuxTerm() )
    return false;

  linux_console_cursor_style = style;

  if ( fterm_data->isCursorHidden() )
    return false;

  setLinuxCursorStyle(style);
  return true;
}

//----------------------------------------------------------------------
void FTermLinux::setUTF8 (bool enable) const
{
  if ( ! FTerm::isLinuxTerm() )
    return;

  if ( enable )
    FTerm::putstring (ESC "%G");
  else
    FTerm::putstring (ESC "%@");

  std::fflush(stdout);
}

//----------------------------------------------------------------------
#if defined(ISA_SYSCTL_SUPPORT)
bool FTermLinux::setPalette (FColor index, int r, int g, int b)
{
  if ( ! FTerm::isLinuxTerm() )
    return false;

  return setVGAPalette (index, r, g, b);
}
#else
bool FTermLinux::setPalette (FColor, int, int, int)
{
  return false;
}
#endif

//----------------------------------------------------------------------
bool FTermLinux::isLinuxConsole()
{
  // Check if it's a Linux console

  if ( ! fsystem )
    fsystem = FTerm::getFSystem();

  char arg{0};
  const int fd_tty = FTerm::getTTYFileDescriptor();

  // Get keyboard type an compare
  return ( fsystem->isTTY(fd_tty)
        && fsystem->ioctl(fd_tty, KDGKBTYPE, &arg) == 0
        && ((arg == KB_101) || (arg == KB_84)) );
}

//----------------------------------------------------------------------
void FTermLinux::init()
{
  // Initialize Linux console

  if ( ! fsystem )
    fsystem = FTerm::getFSystem();

  if ( ! fterm_data )
    fterm_data = FTerm::getFTermData();

  fsystem = FTerm::getFSystem();
  term_detection = FTerm::getFTermDetection();
  screen_unicode_map.entries = nullptr;
  screen_font.data = nullptr;
  fterm_data->supportShadowCharacter (true);
  fterm_data->supportHalfBlockCharacter (true);

#if defined(ISA_SYSCTL_SUPPORT)
  getVGAPalette();
#endif

  if ( FTerm::openConsole() == 0 )
  {
    term_detection->setLinuxTerm (isLinuxConsole());

    if ( FTerm::isLinuxTerm() )
    {
      getUnicodeMap();
      getScreenFont();

#if defined(ISA_SYSCTL_SUPPORT)
      // Enable 16 background colors
      if ( setBlinkAsIntensity(true) == 0 )
        FTermcap::max_color = 16;
      else
        FTermcap::max_color = 8;
#endif
      // Underline cursor
      setCursorStyle (fc::underscore_cursor);

      // Framebuffer color depth in bits per pixel
      framebuffer_bpp = getFramebuffer_bpp();

      // More than 4 bits per pixel and the font uses the blink-bit
      if ( framebuffer_bpp >= 4 && screen_font.charcount <= 256 )
        FTermcap::max_color = 16;
    }

    FTerm::detectTermSize();
    FTerm::closeConsole();
  }
  else
  {
    std::clog << FLog::Error << "Can not open the console." << std::endl;
    std::abort();
  }
}

//----------------------------------------------------------------------
void FTermLinux::initCharMap()
{
  constexpr sInt16 NOT_FOUND = -1;

  if ( new_font || vga_font )
    return;

  if ( screen_unicode_map.entry_ct > 0 && screen_unicode_map.entries )
  {
    for (std::size_t i{0}; i <= fc::last_char_item; i++ )
    {
      const auto ucs = wchar_t(fc::character[i][fc::UTF8]);
      const sInt16 fontpos = getFontPos(ucs);

      // Fix for a non-cp437 Linux console with PC charset encoding
      if ( fontpos > 255 || fontpos == NOT_FOUND )
        fc::character[i][fc::PC] = fc::character[i][fc::ASCII];

      // Character substitutions for missing characters
      if ( fontpos == NOT_FOUND )
      {
        characterFallback (ucs, { L'▲', L'↑', L'^' });
        characterFallback (ucs, { L'▼', L'↓', L'v' });
        characterFallback (ucs, { L'►', L'▶', L'→', L'>' });
        characterFallback (ucs, { L'◄', L'◀', L'←', L'<' });
        characterFallback (ucs, { L'●', L'◆', L'⬤', L'*' });
        characterFallback (ucs, { L'•', L'●', L'◆', L'⬤', L'*' });
        characterFallback (ucs, { L'×', L'❌', L'x' });
        characterFallback (ucs, { L'÷', L'➗', L'/' });
        characterFallback (ucs, { L'√', L'✓', L'x' });
        characterFallback (ucs, { L'ˣ', L'ⁿ', L'ˆ', L'`' });
      }
    }
  }

  initSpecialCharacter();
}

//----------------------------------------------------------------------
void FTermLinux::finish()
{
  if ( FTerm::isLinuxTerm() )
  {
#if defined(ISA_SYSCTL_SUPPORT)
    setBlinkAsIntensity (false);
#endif
    setLinuxCursorStyle (fc::default_cursor);
  }
}

//----------------------------------------------------------------------
bool FTermLinux::loadVGAFont()
{
  vga_font = true;
  new_font = false;

  if ( FTerm::openConsole() == 0 )
  {
    if ( isLinuxConsole() )
    {
      // Set the standard vga font 8x16
      const int ret = setScreenFont(fc::__8x16std, 256, 8, 16);

      if ( ret != 0 )
        vga_font = false;

      // Unicode character mapping
      struct unimapdesc unimap;
      unimap.entry_ct = uInt16 ( sizeof(fc::unicode_cp437_pairs)
                               / sizeof(unipair) );
      unimap.entries = const_cast<unipair*>(&fc::unicode_cp437_pairs[0]);
      setUnicodeMap(&unimap);
    }
    else
      vga_font = false;

    FTerm::detectTermSize();
    FTerm::closeConsole();
  }
  else
    vga_font = false;

  if ( vga_font )
  {
    if ( ! fterm_data )
      fterm_data = FTerm::getFTermData();

    fterm_data->supportShadowCharacter (true);
    fterm_data->supportHalfBlockCharacter (true);
  }

  return vga_font;
}

//----------------------------------------------------------------------
bool FTermLinux::loadNewFont()
{
  new_font = true;
  vga_font = false;

  if ( FTerm::openConsole() == 0 )
  {
    if ( isLinuxConsole() )
    {
      // Set the graphical font
      int ret;

      if ( has9BitCharacters() )
        ret = setScreenFont(fc::__9x16graph, 256, 8, 16);  // set 9×16
      else
        ret = setScreenFont(fc::__8x16graph, 256, 8, 16);  // set 8×16

      if ( ret != 0 )
        new_font = false;

      // Unicode character mapping
      struct unimapdesc unimap;
      unimap.entry_ct = uInt16 ( sizeof(fc::unicode_newfont_pairs)
                               / sizeof(unipair) );
      unimap.entries = const_cast<unipair*>(&fc::unicode_newfont_pairs[0]);
      setUnicodeMap(&unimap);
    }
    else
      new_font = false;

    FTerm::detectTermSize();
    FTerm::closeConsole();
  }
  else
    new_font = false;

  if ( new_font )
  {
    if ( ! fterm_data )
      fterm_data = FTerm::getFTermData();

    fterm_data->supportShadowCharacter (true);
    fterm_data->supportHalfBlockCharacter (true);
  }

  return new_font;
}

//----------------------------------------------------------------------
bool FTermLinux::loadOldFont()
{
  bool retval{false};

  if ( FTerm::openConsole() == 0 )
  {
    if ( isLinuxConsole() )
    {
      if ( screen_font.data )
      {
        const int ret = setScreenFont ( screen_font.data
                                      , screen_font.charcount
                                      , screen_font.width
                                      , screen_font.height
                                      , true );
        delete[] screen_font.data;
        screen_font.data = nullptr;

        if ( ret == 0 )
          retval = true;
      }

      if ( screen_unicode_map.entries )
      {
        setUnicodeMap (&screen_unicode_map);
        initCharMap();
        delete[] screen_unicode_map.entries;
        screen_unicode_map.entries = nullptr;
      }
    }

    FTerm::detectTermSize();
    FTerm::closeConsole();
  }

  if ( retval )
    vga_font = new_font = false;

  return retval;
}

//----------------------------------------------------------------------
bool FTermLinux::saveColorMap()
{
  if ( ! FTerm::isLinuxTerm() )
    return false;

#if defined(ISA_SYSCTL_SUPPORT)
  return saveVGAPalette();
#else
  return false;
#endif
}

//----------------------------------------------------------------------
bool FTermLinux::resetColorMap()
{
  if ( ! FTerm::isLinuxTerm() )
    return false;

#if defined(ISA_SYSCTL_SUPPORT)
  return resetVGAPalette();
#else
  return false;
#endif
}

//----------------------------------------------------------------------
void FTermLinux::setBeep (int Hz, int ms) const
{
  if ( ! FTerm::isLinuxTerm() )
    return;

  // Range for frequency: 21-32766
  if ( Hz < 21 || Hz > 32766 )
    return;

  // Range for duration:  0-1999
  if ( ms < 0 || ms > 1999 )
    return;

  FTerm::putstringf ( CSI "10;%d]"
                      CSI "11;%d]"
                    , Hz, ms );
  std::fflush(stdout);
}

//----------------------------------------------------------------------
void FTermLinux::resetBeep() const
{
  if ( ! FTerm::isLinuxTerm() )
    return;

  // Default frequency: 750 Hz
  // Default duration:  125 ms
  FTerm::putstring ( CSI "10;750]"
                     CSI "11;125]" );
  std::fflush(stdout);
}

//----------------------------------------------------------------------
FKey FTermLinux::modifierKeyCorrection (const FKey& key_id)
{
  // Get the current modifier key state

  if ( ! fsystem )
    fsystem = FTerm::getFSystem();

  const modifier_key& m = getModifierKey();

  if ( ! (m.shift || m.ctrl || m.alt) )
  {
    return key_id;
  }
  else if ( m.shift && ! m.ctrl && ! m.alt )
  {
    return shiftKeyCorrection(key_id);
  }
  else if ( ! m.shift && m.ctrl && ! m.alt )
  {
    return ctrlKeyCorrection(key_id);
  }
  else if ( ! m.shift && ! m.ctrl && m.alt )
  {
    return altKeyCorrection(key_id);
  }
  else if ( m.shift && m.ctrl && ! m.alt )
  {
    return shiftCtrlKeyCorrection(key_id);
  }
  else if ( m.shift && ! m.ctrl && m.alt )
  {
    return shiftAltKeyCorrection(key_id);
  }
  else if ( ! m.shift && m.ctrl && m.alt )
  {
    return ctrlAltKeyCorrection(key_id);
  }
  else if ( m.shift &&  m.ctrl && m.alt )
  {
    return shiftCtrlAltKeyCorrection(key_id);
  }

  return key_id;
}


// private methods of FTermLinux
//----------------------------------------------------------------------
int FTermLinux::getFramebuffer_bpp()
{
  int fd{-1};
  const char* fb = "/dev/fb/0";
  struct fb_var_screeninfo fb_var{};
  struct fb_fix_screeninfo fb_fix{};

  if ( ! fsystem )
    fsystem = FTerm::getFSystem();

  if ( (fd = fsystem->open(fb, O_RDWR)) < 0 )
  {
    if ( errno != ENOENT && errno != ENOTDIR )
      return -1;

    fb = "/dev/fb0";

    if ( (fd = fsystem->open(fb, O_RDWR)) < 0 )
      return -1;
  }

  if ( fsystem->ioctl(fd, FBIOGET_VSCREENINFO, &fb_var) == 0
    && fsystem->ioctl(fd, FBIOGET_FSCREENINFO, &fb_fix) == 0 )
  {
    fsystem->close(fd);
    return int(fb_var.bits_per_pixel);
  }
  else
  {
    fsystem->close(fd);
  }

  return -1;
}

//----------------------------------------------------------------------
bool FTermLinux::getScreenFont()
{
  struct console_font_op font{};
  const int fd_tty = FTerm::getTTYFileDescriptor();
  int ret{-1};

  if ( fd_tty < 0 )
    return false;

  // Initialize unused padding bytes in struct
  std::memset (&font, 0, sizeof(console_font_op));

  font.op = KD_FONT_OP_GET;
  font.flags = 0;
  font.width = 32;
  font.height = 32;
  font.charcount = 512;

  // Initialize with 0
  try
  {
    static constexpr std::size_t data_size = 4 * 32 * 512;
    font.data = new uChar[data_size]();
  }
  catch (const std::bad_alloc&)
  {
    badAllocOutput ("FString");
    return false;
  }

  // Font operation
  if ( fsystem )
    ret = fsystem->ioctl (fd_tty, KDFONTOP, &font);

  if ( ret != 0 )
  {
    if ( font.data )
      delete[] font.data;

    return false;
  }

  screen_font.width = font.width;
  screen_font.height = font.height;
  screen_font.charcount = font.charcount;
  screen_font.data = font.data;
  return true;
}

//----------------------------------------------------------------------
bool FTermLinux::getUnicodeMap()
{
  const int fd_tty = FTerm::getTTYFileDescriptor();
  int ret{-1};

  if ( fd_tty < 0 )
    return false;

  screen_unicode_map.entry_ct = 0;
  screen_unicode_map.entries = nullptr;

  // Get count
  if ( fsystem )
    ret = fsystem->ioctl (fd_tty, GIO_UNIMAP, &screen_unicode_map);

  if ( ret != 0 )
  {
    const std::size_t count = screen_unicode_map.entry_ct;

    if ( errno != ENOMEM || count == 0 )
      return false;

    try
    {
      screen_unicode_map.entries = new struct unipair[count]();
    }
    catch (const std::bad_alloc&)
    {
      badAllocOutput ("unipair[count]");
      return false;
    }

    // Get unicode-to-font mapping from kernel
    if ( fsystem )
      ret = fsystem->ioctl (fd_tty, GIO_UNIMAP, &screen_unicode_map);

    if ( ret != 0 )
      return false;
  }

  return true;
}

//----------------------------------------------------------------------
FTermLinux::modifier_key& FTermLinux::getModifierKey()
{
  // Get Linux console shift state

  char subcode{6};  // Shift state command + return value

  // Fill bit field with 0
  std::memset (&mod_key, 0x00, sizeof(mod_key));

  // TIOCLINUX, subcode = 6 (TIOCL_GETSHIFTSTATE)
  if ( fsystem && fsystem->ioctl(0, TIOCLINUX, &subcode) >= 0 )
  {
    if ( subcode & (1 << KG_SHIFT) )
      mod_key.shift = true;

    if ( subcode & (1 << KG_ALTGR) )
      mod_key.alt_gr = true;

    if ( subcode & (1 << KG_CTRL) )
      mod_key.ctrl = true;

    if ( subcode & (1 << KG_ALT) )
      mod_key.alt = true;
  }

  return mod_key;
}

//----------------------------------------------------------------------
int FTermLinux::setScreenFont ( const uChar fontdata[], uInt count
                              , uInt fontwidth, uInt fontheight
                              , bool direct)
{
  struct console_font_op font{};
  const int fd_tty = FTerm::getTTYFileDescriptor();
  int ret{-1};

  if ( fd_tty < 0 )
    return -1;

  // Initialize unused padding bytes in struct
  std::memset (&font, 0x00, sizeof(console_font_op));

  font.op = KD_FONT_OP_SET;
  font.flags = 0;
  font.width = fontwidth;
  font.height = fontheight;
  font.charcount = count;

  if ( direct )
    font.data = const_cast<uChar*>(fontdata);
  else
  {
    const std::size_t bytes_per_line = font.width / 8;
    const std::size_t data_size = bytes_per_line * 32 * font.charcount;

    try
    {
      font.data = new uChar[data_size]();  // Initialize with 0
    }
    catch (const std::bad_alloc&)
    {
      badAllocOutput ("uChar[data_size]");
      return -1;
    }

    for (std::size_t i{0}; i < count; i++)
      std::memcpy ( font.data + bytes_per_line * 32 * i
                  , &fontdata[i * font.height]
                  , font.height);
  }

  // Font operation
  if ( fsystem )
    ret = fsystem->ioctl (fd_tty, KDFONTOP, &font);

  if ( ret != 0 && errno != ENOSYS && errno != EINVAL )
  {
    if ( ! direct )
      delete[] font.data;

    return -1;
  }

  if ( ! direct )
    delete[] font.data;

  if ( ret == 0 )
    return 0;
  else
    return -1;
}

//----------------------------------------------------------------------
int FTermLinux::setUnicodeMap (struct unimapdesc* unimap)
{
  struct unimapinit advice;
  const int fd_tty = FTerm::getTTYFileDescriptor();
  int ret{-1};

  if ( fd_tty < 0 )
    return -1;

  advice.advised_hashsize = 0;
  advice.advised_hashstep = 0;
  advice.advised_hashlevel = 0;

  do
  {
    // Clear the unicode-to-font table
    if ( fsystem )
      ret = fsystem->ioctl (fd_tty, PIO_UNIMAPCLR, &advice);

    if ( ret != 0 )
      return -1;

    // Put the new unicode-to-font mapping in kernel
    if ( fsystem )
      ret = fsystem->ioctl (fd_tty, PIO_UNIMAP, unimap);

    if ( ret != 0 )
      advice.advised_hashlevel++;
  }
  while ( ret != 0 && errno == ENOMEM && advice.advised_hashlevel < 100);

  if ( ret == 0 )
    return 0;
  else
    return -1;
}

//----------------------------------------------------------------------
void FTermLinux::setLinuxCursorStyle (CursorStyle style) const
{
  FTerm::putstringf (CSI "?%dc", style);
}

#if defined(ISA_SYSCTL_SUPPORT)
//----------------------------------------------------------------------
inline uInt16 FTermLinux::getInputStatusRegisterOne()
{
  // Gets the VGA input-status-register-1

  if ( ! fsystem )
    fsystem = FTerm::getFSystem();

  // Miscellaneous output (read port)
  static constexpr uInt16 misc_read = 0x3cc;
  const uChar misc_value = fsystem->inPortByte(misc_read);
  const uInt16 io_base = ( misc_value & 0x01 ) ? 0x3d0 : 0x3b0;
  // 0x3ba : Input status 1 mono/MDA (read port)
  // 0x3da : Input status 1 color/CGA (read port)
  return io_base + 0x0a;
}

//----------------------------------------------------------------------
uChar FTermLinux::readAttributeController (uChar index)
{
  // Reads a byte from the attribute controller from a given index

  if ( ! fsystem )
    fsystem = FTerm::getFSystem();

  // Attribute controller (write port)
  static constexpr uInt16 attrib_cntlr_write = 0x3c0;
  // Attribute controller (read port)
  static constexpr uInt16 attrib_cntlr_read  = 0x3c1;
  const uInt16 input_status_1 = getInputStatusRegisterOne();

  fsystem->inPortByte (input_status_1);  // switch to index mode
  fsystem->outPortByte (index & 0x1f, attrib_cntlr_write);  // selects address register
  const uChar res = fsystem->inPortByte (attrib_cntlr_read);  // read from data register

  // Disable access to the palette and unblank the display
  fsystem->inPortByte (input_status_1);  // switch to index mode
  index = (index & 0x1f) | 0x20;  // set bit 5 (enable display)
  fsystem->outPortByte (index, attrib_cntlr_write);
  fsystem->inPortByte (attrib_cntlr_read);

  return res;
}

//----------------------------------------------------------------------
void FTermLinux::writeAttributeController (uChar index, uChar data)
{
  // Writes a byte from the attribute controller from a given index

  if ( ! fsystem )
    fsystem = FTerm::getFSystem();

  // Attribute controller (write port)
  static constexpr uInt16 attrib_cntlr_write = 0x3c0;
  const uInt16 input_status_1 = getInputStatusRegisterOne();

  fsystem->inPortByte (input_status_1);  // switch to index mode
  fsystem->outPortByte (index & 0x1f, attrib_cntlr_write);  // selects address register
  fsystem->outPortByte (data, attrib_cntlr_write);  // write to data register

  // Disable access to the palette and unblank the display
  fsystem->inPortByte (input_status_1);  // switch to index mode
  index = (index & 0x1f) | 0x20;  // set bit 5 (enable display)
  fsystem->outPortByte (index, attrib_cntlr_write);
  fsystem->outPortByte (data, attrib_cntlr_write);
}

//----------------------------------------------------------------------
inline uChar FTermLinux::getAttributeMode()
{
  // Gets the attribute mode value from the vga attribute controller
  static constexpr uChar attrib_mode = 0x10;
  return readAttributeController(attrib_mode);
}

//----------------------------------------------------------------------
inline void FTermLinux::setAttributeMode (uChar data)
{
  // Sets the attribute mode value from the vga attribute controller
  static constexpr uChar attrib_mode = 0x10;
  writeAttributeController (attrib_mode, data);
}

//----------------------------------------------------------------------
int FTermLinux::setBlinkAsIntensity (bool enable)
{
  // Uses blink-bit as background intensity.
  // That permits 16 colors for background

  if ( ! fsystem )
    fsystem = FTerm::getFSystem();

  const int fd_tty = FTerm::getTTYFileDescriptor();

  // Test if the blink-bit is used by the screen font (512 characters)
  if ( screen_font.charcount > 256 )
    return -1;

  if ( fsystem->getuid() != 0 )  // Direct hardware access requires root privileges
    return -2;

  if ( fd_tty < 0 )
    return -1;

  // Enable access to VGA I/O ports  (from 0x3B4 with num = 0x2C)
  if ( fsystem->ioctl(fd_tty, KDENABIO, 0) < 0 )
    return -1;  // error on KDENABIO

  if ( enable )
    setAttributeMode (getAttributeMode() & 0xF7);  // clear bit 3
  else
    setAttributeMode (getAttributeMode() | 0x08);  // set bit 3

  // Disable access to VGA I/O ports
  if ( fsystem->ioctl(fd_tty, KDDISABIO, 0) < 0 )
    return -1;  // error on KDDISABIO

  return 0;
}

//----------------------------------------------------------------------
bool FTermLinux::has9BitCharacters()
{
  // Are 9-bit wide characters used?

  // 9-bit character:
  //  0xc0...0xdf - copying the eighth pixel into the ninth pixel
  //     The rest - the ninth pixel has the background color

  if ( ! fsystem )
    fsystem = FTerm::getFSystem();

  const int fd_tty = FTerm::getTTYFileDescriptor();

  if ( fsystem->getuid() != 0 )  // Direct hardware access requires root privileges
    return false;

  if ( fd_tty < 0 )
    return false;

  // Enable access to VGA I/O ports  (from 0x3B4 with num = 0x2C)
  if ( fsystem->ioctl(fd_tty, KDENABIO, 0) < 0 )
    return false;  // error on KDENABIO

  const bool nine_bit_char( getAttributeMode() & 0x04 );

    // Disable access to VGA I/O ports
  if ( fsystem->ioctl(fd_tty, KDDISABIO, 0) < 0 )
    return false;  // error on KDDISABIO

  return nine_bit_char;
}

//----------------------------------------------------------------------
void FTermLinux::getVGAPalette()
{
  if ( fsystem && fsystem->ioctl(0, GIO_CMAP, &cmap) != 0 )
    setVGADefaultPalette();  // Fallback, if GIO_CMAP does not work
}

//----------------------------------------------------------------------
void FTermLinux::setVGADefaultPalette()
{
  constexpr rgb defaultColor[16] =
  {
    {0x00, 0x00, 0x00}, {0xaa, 0x00, 0x00},
    {0x00, 0xaa, 0x00}, {0xaa, 0x55, 0x00},
    {0x00, 0x00, 0xaa}, {0xaa, 0x00, 0xaa},
    {0x00, 0xaa, 0xaa}, {0xaa, 0xaa, 0xaa},
    {0x55, 0x55, 0x55}, {0xff, 0x55, 0x55},
    {0x55, 0xff, 0x55}, {0xff, 0xff, 0x55},
    {0x55, 0x55, 0xff}, {0xff, 0x55, 0xff},
    {0x55, 0xff, 0xff}, {0xff, 0xff, 0xff}
  };

  for (std::size_t index{0}; index < 16; index++)
  {
    cmap.color[index].red   = defaultColor[index].red;
    cmap.color[index].green = defaultColor[index].green;
    cmap.color[index].blue  = defaultColor[index].blue;
  }
}

//----------------------------------------------------------------------
bool FTermLinux::setVGAPalette (FColor index, int r, int g, int b)
{
  // Set the vga color map

  if ( r >= 0 && r < 256
    && g >= 0 && g < 256
    && b >= 0 && b < 256 )
  {
    cmap.color[index].red   = uChar(r);
    cmap.color[index].green = uChar(g);
    cmap.color[index].blue  = uChar(b);
  }

  if ( fsystem && fsystem->ioctl(0, PIO_CMAP, &cmap) == 0 )
    return true;
  else
    return false;
}

//----------------------------------------------------------------------
bool FTermLinux::saveVGAPalette()
{
  // Save the current vga color map

  if ( fsystem && fsystem->ioctl(0, GIO_CMAP, &saved_color_map) == 0 )
    has_saved_palette = true;
  else
    has_saved_palette = false;

  return has_saved_palette;
}

//----------------------------------------------------------------------
bool FTermLinux::resetVGAPalette()
{
  // Reset the vga color map

  if ( has_saved_palette )
  {
    if ( fsystem && fsystem->ioctl (0, PIO_CMAP, &saved_color_map) )
      return false;
  }
  else
  {
    setVGADefaultPalette();

    if ( fsystem && fsystem->ioctl(0, PIO_CMAP, &cmap) != 0 )
      return false;
  }

  return true;
}
#endif  // defined(ISA_SYSCTL_SUPPORT)

//----------------------------------------------------------------------
FKey FTermLinux::shiftKeyCorrection (const FKey& key_id) const
{
  switch ( key_id )
  {
    case fc::Fkey_up:
      return fc::Fkey_sr;         // Shift+Up

    case fc::Fkey_down:
      return fc::Fkey_sf;         // Shift+Down

    case fc::Fkey_left:
      return fc::Fkey_sleft;      // Shift+Left

    case fc::Fkey_right:
      return fc::Fkey_sright;     // Shift+Right

    case fc::Fkey_ic:
      return fc::Fkey_sic;        // Shift+Ins

    case fc::Fkey_dc:
      return fc::Fkey_sdc;        // Shift+Del

    case fc::Fkey_home:
      return fc::Fkey_shome;      // Shift+Home

    case fc::Fkey_end:
      return fc::Fkey_send;       // Shift+End

    case fc::Fkey_ppage:
      return fc::Fkey_sprevious;  // Shift+PgUp

    case fc::Fkey_npage:
      return fc::Fkey_snext;      // Shift+PgDn

    default:
      return key_id;
  }
}

//----------------------------------------------------------------------
FKey FTermLinux::ctrlKeyCorrection (const FKey& key_id) const
{
  switch ( key_id )
  {
    case fc::Fkey_up:
      return fc::Fckey_up;     // Ctrl+Up

    case fc::Fkey_down:
      return fc::Fckey_down;   // Ctrl+Down

    case fc::Fkey_left:
      return fc::Fckey_left;   // Ctrl+Left

    case fc::Fkey_right:
      return fc::Fckey_right;  // Ctrl+Right

    case fc::Fkey_ic:
      return fc::Fckey_ic;     // Ctrl+Ins

    case fc::Fkey_dc:
      return fc::Fckey_dc;     // Ctrl+Del

    case fc::Fkey_home:
      return fc::Fckey_home;   // Ctrl+Home

    case fc::Fkey_end:
      return fc::Fckey_end;    // Ctrl+End

    case fc::Fkey_ppage:
      return fc::Fckey_ppage;  // Ctrl+PgUp

    case fc::Fkey_npage:
      return fc::Fckey_npage;  // Ctrl+PgDn

    default:
      return key_id;
  }
}

//----------------------------------------------------------------------
FKey FTermLinux::altKeyCorrection (const FKey& key_id) const
{
  switch ( key_id )
  {
    case fc::Fkey_up:
      return fc::Fmkey_up;     // Meta+Up

    case fc::Fkey_down:
      return fc::Fmkey_down;   // Meta+Down

    case fc::Fkey_left:
      return fc::Fmkey_left;   // Meta+Left

    case fc::Fkey_right:
      return fc::Fmkey_right;  // Meta+Right

    case fc::Fkey_ic:
      return fc::Fmkey_ic;     // Meta+Ins

    case fc::Fkey_dc:
      return fc::Fmkey_dc;     // Meta+Del

    case fc::Fkey_home:
      return fc::Fmkey_home;   // Meta+Home

    case fc::Fkey_end:
      return fc::Fmkey_end;    // Meta+End

    case fc::Fkey_ppage:
      return fc::Fmkey_ppage;  // Meta+PgUp

    case fc::Fkey_npage:
      return fc::Fmkey_npage;  // Meta+PgDn

    default:
      return key_id;
  }
}

//----------------------------------------------------------------------
FKey FTermLinux::shiftCtrlKeyCorrection (const FKey& key_id) const
{
  switch ( key_id )
  {
    case fc::Fkey_up:
      return fc::Fckey_sup;     // Shift+Ctrl+Up

    case fc::Fkey_down:
      return fc::Fckey_sdown;   // Shift+Ctrl+Down

    case fc::Fkey_left:
      return fc::Fckey_sleft;   // Shift+Ctrl+Left

    case fc::Fkey_right:
      return fc::Fckey_sright;  // Shift+Ctrl+Right

    case fc::Fkey_ic:
      return fc::Fckey_sic;     // Shift+Ctrl+Ins

    case fc::Fkey_dc:
      return fc::Fckey_sdc;     // Shift+Ctrl+Del

    case fc::Fkey_home:
      return fc::Fckey_shome;   // Shift+Ctrl+Home

    case fc::Fkey_end:
      return fc::Fckey_send;    // Shift+Ctrl+End

    case fc::Fkey_ppage:
      return fc::Fckey_sppage;  // Shift+Ctrl+PgUp

    case fc::Fkey_npage:
      return fc::Fckey_snpage;  // Shift+Ctrl+PgDn

    default:
      return key_id;
  }
}

//----------------------------------------------------------------------
FKey FTermLinux::shiftAltKeyCorrection (const FKey& key_id) const
{
  switch ( key_id )
  {
    case fc::Fkey_up:
      return fc::Fmkey_sup;     // Shift+Meta+Up

    case fc::Fkey_down:
      return fc::Fmkey_sdown;   // Shift+Meta+Down

    case fc::Fkey_left:
      return fc::Fmkey_sleft;  // Shift+Meta+Left

    case fc::Fkey_right:
      return fc::Fmkey_sright;   // Shift+Meta+Right

    case fc::Fkey_ic:
      return fc::Fmkey_sic;     // Shift+Meta+Ins

    case fc::Fkey_dc:
      return fc::Fmkey_sdc;     // Shift+Meta+Del

    case fc::Fkey_home:
      return fc::Fmkey_shome;   // Shift+Meta+Home

    case fc::Fkey_end:
      return fc::Fmkey_send;    // Shift+Meta+End

    case fc::Fkey_ppage:
      return fc::Fmkey_sppage;  // Shift+Meta+PgUp

    case fc::Fkey_npage:
      return fc::Fmkey_snpage;  // Shift+Meta+PgDn

    default:
      return key_id;
  }
}

//----------------------------------------------------------------------
FKey FTermLinux::ctrlAltKeyCorrection (const FKey& key_id) const
{
  switch ( key_id )
  {
    case fc::Fkey_up:
      return fc::Fcmkey_up;     // Ctrl+Meta+Up

    case fc::Fkey_down:
      return fc::Fcmkey_down;   // Ctrl+Meta+Down

    case fc::Fkey_left:
      return fc::Fcmkey_left;   // Ctrl+Meta+Left

    case fc::Fkey_right:
      return fc::Fcmkey_right;  // Ctrl+Meta+Right

    case fc::Fkey_ic:
      return fc::Fcmkey_ic;     // Ctrl+Meta+Ins

    case fc::Fkey_dc:
      return fc::Fcmkey_dc;     // Ctrl+Meta+Del

    case fc::Fkey_home:
      return fc::Fcmkey_home;   // Ctrl+Meta+Home

    case fc::Fkey_end:
      return fc::Fcmkey_end;    // Ctrl+Meta+End

    case fc::Fkey_ppage:
      return fc::Fcmkey_ppage;  // Ctrl+Meta+PgUp

    case fc::Fkey_npage:
      return fc::Fcmkey_npage;  // Ctrl+Meta+PgDn

    default:
      return key_id;
  }
}

//----------------------------------------------------------------------
FKey FTermLinux::shiftCtrlAltKeyCorrection (const FKey& key_id) const
{
  switch ( key_id )
  {
    case fc::Fkey_up:
      return fc::Fcmkey_sup;     // Shift+Ctrl+Meta+Up

    case fc::Fkey_down:
      return fc::Fcmkey_sdown;   // Shift+Ctrl+Meta+Down

    case fc::Fkey_left:
      return fc::Fcmkey_sleft;   // Shift+Ctrl+Meta+Left

    case fc::Fkey_right:
      return fc::Fcmkey_sright;  // Shift+Ctrl+Meta+Right

    case fc::Fkey_ic:
      return fc::Fcmkey_sic;     // Shift+Ctrl+Meta+Ins

    case fc::Fkey_dc:
      return fc::Fcmkey_sdc;     // Shift+Ctrl+Meta+Del

    case fc::Fkey_home:
      return fc::Fcmkey_shome;   // Shift+Ctrl+Meta+Home

    case fc::Fkey_end:
      return fc::Fcmkey_send;    // Shift+Ctrl+Meta+End

    case fc::Fkey_ppage:
      return fc::Fcmkey_sppage;  // Shift+Ctrl+Meta+PgUp

    case fc::Fkey_npage:
      return fc::Fcmkey_snpage;  // Shift+Ctrl+Meta+PgDn

    default:
      return key_id;
  }
}

//----------------------------------------------------------------------
inline void FTermLinux::initSpecialCharacter()
{
  const wchar_t c1 = fc::UpperHalfBlock;
  const wchar_t c2 = fc::LowerHalfBlock;
  const wchar_t c3 = fc::FullBlock;

  if ( ! fterm_data )
    fterm_data = FTerm::getFTermData();

  if ( FTerm::charEncode(c1, fc::PC) == FTerm::charEncode(c1, fc::ASCII)
    || FTerm::charEncode(c2, fc::PC) == FTerm::charEncode(c2, fc::ASCII)
    || FTerm::charEncode(c3, fc::PC) == FTerm::charEncode(c3, fc::ASCII) )
  {
    fterm_data->supportShadowCharacter (false);
  }

  const wchar_t c4 = fc::RightHalfBlock;
  const wchar_t c5 = fc::LeftHalfBlock;

  if ( FTerm::charEncode(c4, fc::PC) == FTerm::charEncode(c4, fc::ASCII)
    || FTerm::charEncode(c5, fc::PC) == FTerm::charEncode(c5, fc::ASCII) )
  {
    fterm_data->supportHalfBlockCharacter (false);
  }
}

//----------------------------------------------------------------------
sInt16 FTermLinux::getFontPos (wchar_t ucs) const
{
  constexpr sInt16 NOT_FOUND = -1;

  for (std::size_t n{0}; n < screen_unicode_map.entry_ct; n++)
  {
    if ( screen_unicode_map.entries[n].unicode == ucs )
      return sInt16(screen_unicode_map.entries[n].fontpos);
  }

  return NOT_FOUND;
}

//----------------------------------------------------------------------
void FTermLinux::characterFallback ( wchar_t ucs
                                   , std::vector<wchar_t> fallback )
{
  constexpr sInt16 NOT_FOUND = -1;

  if ( ! fterm_data )
    fterm_data = FTerm::getFTermData();

  charSubstitution& sub_map = fterm_data->getCharSubstitutionMap();

  if ( fallback.size() < 2 || ucs != fallback[0] )
    return;

  for (auto iter = fallback.begin() + 1; iter != fallback.end(); iter++)
  {
    sInt16 pos = getFontPos(*iter);

    if ( pos != NOT_FOUND )
    {
      sub_map[ucs] = *iter;
      return;
    }
  }
}

#endif  // defined(__linux__)

}  // namespace finalcut