////////////////////////////////////////////////////////////////////////
//
// Copyright (C) 2009-2021 The Octave Project Developers
//
// See the file COPYRIGHT.md in the top-level directory of this
// distribution or <https://octave.org/copyright/>.
//
// This file is part of Octave.
//
// Octave is free software: you can redistribute it and/or modify it
// under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// Octave 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 General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with Octave; see the file COPYING.  If not, see
// <https://www.gnu.org/licenses/>.
//
////////////////////////////////////////////////////////////////////////

#if defined (HAVE_CONFIG_H)
#  include "config.h"
#endif

#include "base-text-renderer.h"
#include "ft-text-renderer.h"

#if defined (HAVE_FREETYPE)

#if defined (HAVE_PRAGMA_GCC_DIAGNOSTIC)
#  pragma GCC diagnostic push
#  pragma GCC diagnostic ignored "-Wold-style-cast"
#endif

#include <ft2build.h>
#include FT_FREETYPE_H
#include FT_GLYPH_H

#if defined (HAVE_FONTCONFIG)
#  include <fontconfig/fontconfig.h>
#endif

#if defined (HAVE_PRAGMA_GCC_DIAGNOSTIC)
#  pragma GCC diagnostic pop
#endif

#include <clocale>
#include <cwchar>
#include <map>
#include <utility>

#include "singleton-cleanup.h"
#include "unistr-wrappers.h"

#include "defaults.h"
#include "error.h"
#include "file-ops.h"
#include "oct-env.h"
#include "pr-output.h"
#include "text-renderer.h"

namespace octave
{
  // FIXME: maybe issue at most one warning per glyph/font/size/weight
  //        combination.

  static void
  warn_missing_glyph (FT_ULong c)
  {
    warning_with_id ("Octave:missing-glyph",
                     "text_renderer: skipping missing glyph for character '%lx'", c);
  }

  static void
  warn_glyph_render (FT_ULong c)
  {
    warning_with_id ("Octave:glyph-render",
                     "text_renderer: unable to render glyph for character '%lx'", c);
  }

#if defined (_MSC_VER)
  // FIXME: is this really needed?
  //
  // This is just a trick to avoid multiple symbol definitions.
  // PermMatrix.h contains a dllexport'ed Array<octave_idx_type>
  // that will cause MSVC not to generate a new instantiation and
  // use the imported one instead.
#  include "PermMatrix.h"
#endif

  // Forward declaration
  static void ft_face_destroyed (void *object);

  class
  ft_manager
  {
  private:

    ft_manager (void)
      : library (), freetype_initialized (false), fontconfig_initialized (false)
    {
      if (FT_Init_FreeType (&library))
        error ("unable to initialize FreeType library");
      else
        freetype_initialized = true;

#if defined (HAVE_FONTCONFIG)
      if (! FcInit ())
        error ("unable to initialize fontconfig library");
      else
        fontconfig_initialized = true;
#endif
    }

  public:

    // No copying!

    ft_manager (const ft_manager&) = delete;

    ft_manager& operator = (const ft_manager&) = delete;

  private:

    ~ft_manager (void)
    {
      if (freetype_initialized)
        FT_Done_FreeType (library);

#if defined (HAVE_FONTCONFIG)
      // FIXME: Skip the call to FcFini because it can trigger the assertion
      //
      //   octave: fccache.c:507: FcCacheFini: Assertion 'fcCacheChains[i] == ((void *)0)' failed.
      //
      // if (fontconfig_initialized)
      //   FcFini ();
#endif
    }

  public:

    static bool instance_ok (void)
    {
      bool retval = true;

      if (! instance)
        {
          instance = new ft_manager ();
          singleton_cleanup_list::add (cleanup_instance);
        }

      return retval;
    }

    static void cleanup_instance (void) { delete instance; instance = nullptr; }

    static FT_Face get_font (const std::string& name, const std::string& weight,
                             const std::string& angle, double size)
    {
      return (instance_ok ()
              ? instance->do_get_font (name, weight, angle, size)
              : nullptr);
    }

    static octave_map get_system_fonts (void)
    {
      return (instance_ok ()
              ? instance->do_get_system_fonts ()
              : octave_map ());
    }

    static void font_destroyed (FT_Face face)
    {
      if (instance_ok ())
        instance->do_font_destroyed (face);
    }

  private:

    static ft_manager *instance;

    typedef std::pair<std::string, double> ft_key;
    typedef std::map<ft_key, FT_Face> ft_cache;

    // Cache the fonts loaded by FreeType.  This cache only contains
    // weak references to the fonts, strong references are only present
    // in class text_renderer.
    ft_cache cache;

    static octave_map do_get_system_fonts (void)
    {
      static octave_map font_map;

      if (font_map.isempty ())
        {
#if defined (HAVE_FONTCONFIG)
          FcConfig *config = FcConfigGetCurrent();
          FcPattern *pat = FcPatternCreate ();
          FcObjectSet *os = FcObjectSetBuild (FC_FAMILY, FC_SLANT, FC_WEIGHT,
                                              FC_CHARSET, nullptr);
          FcFontSet *fs = FcFontList (config, pat, os);

          if (fs->nfont > 0)
            {
              // Mark fonts that have at least all printable ASCII chars
              FcCharSet *minimal_charset =  FcCharSetCreate ();
              for (int i = 32; i < 127; i++)
                FcCharSetAddChar (minimal_charset, static_cast<FcChar32> (i));

              string_vector fields (4);
              fields(0) = "family";
              fields(1) = "angle";
              fields(2) = "weight";
              fields(3) = "suitable";

              dim_vector dv (1, fs->nfont);
              Cell families (dv);
              Cell angles (dv);
              Cell weights (dv);
              Cell suitable (dv);

              unsigned char *family;
              int val;
              for (int i = 0; fs && i < fs->nfont; i++)
                {
                  FcPattern *font = fs->fonts[i];
                  if (FcPatternGetString (font, FC_FAMILY, 0, &family)
                      == FcResultMatch)
                    families(i) = std::string (reinterpret_cast<char*> (family));
                  else
                    families(i) = "unknown";

                  if (FcPatternGetInteger (font, FC_SLANT, 0, &val)
                      == FcResultMatch)
                    angles(i) = (val == FC_SLANT_ITALIC
                                 || val == FC_SLANT_OBLIQUE)
                                ? "italic" : "normal";
                  else
                    angles(i) = "unknown";

                  if (FcPatternGetInteger (font, FC_WEIGHT, 0, &val)
                      == FcResultMatch)
                    weights(i) = (val == FC_WEIGHT_BOLD
                                  || val == FC_WEIGHT_DEMIBOLD)
                                 ? "bold" : "normal";
                  else
                    weights(i) = "unknown";

                  FcCharSet *cset;
                  if (FcPatternGetCharSet (font, FC_CHARSET, 0, &cset)
                      == FcResultMatch)
                    suitable(i) = (FcCharSetIsSubset (minimal_charset, cset)
                                   ? true : false);
                  else
                    suitable(i) = false;
                }

              font_map = octave_map (dv, fields);

              font_map.assign ("family", families);
              font_map.assign ("angle", angles);
              font_map.assign ("weight", weights);
              font_map.assign ("suitable", suitable);

              if (fs)
                FcFontSetDestroy (fs);
            }
#endif
        }

      return font_map;
    }

    FT_Face do_get_font (const std::string& name, const std::string& weight,
                         const std::string& angle, double size)
    {
      FT_Face retval = nullptr;

#if defined (HAVE_FT_REFERENCE_FACE)
      // Look first into the font cache, then use fontconfig.  If the font
      // is present in the cache, simply add a reference and return it.

      ft_key key (name + ':' + weight + ':' + angle, size);
      ft_cache::const_iterator it = cache.find (key);

      if (it != cache.end ())
        {
          FT_Reference_Face (it->second);
          return it->second;
        }
#endif

      static std::string fonts_dir;

      if (fonts_dir.empty ())
        {
          fonts_dir = sys::env::getenv ("OCTAVE_FONTS_DIR");

          if (fonts_dir.empty ())
#if defined (SYSTEM_FREEFONT_DIR)
            fonts_dir = SYSTEM_FREEFONT_DIR;
#else
            fonts_dir = config::oct_fonts_dir ();
#endif
        }


      // Default font file
      std::string file;

      if (! fonts_dir.empty ())
        {
          file = fonts_dir + sys::file_ops::dir_sep_str () + "FreeSans";

          if (weight == "bold")
            file += "Bold";

          if (angle == "italic" || angle == "oblique")
            file += "Oblique";

          file += ".otf";
        }

#if defined (HAVE_FONTCONFIG)
      if (name != "*" && fontconfig_initialized)
        {
          int fc_weight, fc_angle;

          if (weight == "bold")
            fc_weight = FC_WEIGHT_BOLD;
          else
            fc_weight = FC_WEIGHT_NORMAL;

          if (angle == "italic")
            fc_angle = FC_SLANT_ITALIC;
          else if (angle == "oblique")
            fc_angle = FC_SLANT_OBLIQUE;
          else
            fc_angle = FC_SLANT_ROMAN;

          FcPattern *pat = FcPatternCreate ();

          FcPatternAddString (pat, FC_FAMILY,
                              (reinterpret_cast<const FcChar8 *>
                               (name.c_str ())));

          FcPatternAddInteger (pat, FC_WEIGHT, fc_weight);
          FcPatternAddInteger (pat, FC_SLANT, fc_angle);
          FcPatternAddDouble (pat, FC_PIXEL_SIZE, size);

          if (FcConfigSubstitute (nullptr, pat, FcMatchPattern))
            {
              FcResult res;
              FcPattern *match;

              FcDefaultSubstitute (pat);
              match = FcFontMatch (nullptr, pat, &res);

              // FIXME: originally, this test also required that
              // res != FcResultNoMatch.  Is that really needed?
              if (match)
                {
                  unsigned char *tmp;

                  FcPatternGetString (match, FC_FILE, 0, &tmp);
                  file = reinterpret_cast<char *> (tmp);
                }
              else
                ::warning ("could not match any font: %s-%s-%s-%g, using default font",
                           name.c_str (), weight.c_str (), angle.c_str (),
                           size);

              if (match)
                FcPatternDestroy (match);
            }

          FcPatternDestroy (pat);
        }
#endif

      if (file.empty ())
        ::warning ("unable to find default font files");
      else
        {
          if (FT_New_Face (library, file.c_str (), 0, &retval))
            ::warning ("ft_manager: unable to load font: %s", file.c_str ());
#if defined (HAVE_FT_REFERENCE_FACE)
          else
            {
              // Install a finalizer to notify ft_manager that the font is
              // being destroyed.  The class ft_manager only keeps weak
              // references to font objects.

              retval->generic.data = new ft_key (key);
              retval->generic.finalizer = ft_face_destroyed;

              // Insert loaded font into the cache.
              if (FT_Reference_Face (retval) == 0)
                cache[key] = retval;
            }
#endif
        }

      return retval;
    }

    void do_font_destroyed (FT_Face face)
    {
      if (face->generic.data)
        {
          ft_key *pkey = reinterpret_cast<ft_key *> (face->generic.data);

          cache.erase (*pkey);
          delete pkey;
          face->generic.data = nullptr;
          FT_Done_Face (face);
        }
    }

  private:
    FT_Library library;
    bool freetype_initialized;
    bool fontconfig_initialized;
  };

  ft_manager *ft_manager::instance = nullptr;

  static void
  ft_face_destroyed (void *object)
  {
    ft_manager::font_destroyed (reinterpret_cast<FT_Face> (object));
  }

  class
  OCTINTERP_API
  ft_text_renderer : public base_text_renderer
  {
  public:

    enum
    {
      MODE_BBOX   = 0,
      MODE_RENDER = 1
    };

    enum
    {
      ROTATION_0   = 0,
      ROTATION_90  = 1,
      ROTATION_180 = 2,
      ROTATION_270 = 3
    };

  public:

    ft_text_renderer (void)
      : base_text_renderer (), font (), bbox (1, 4, 0.0), halign (0),
        xoffset (0), line_yoffset (0), yoffset (0), mode (MODE_BBOX),
        color (dim_vector (1, 3), 0), m_do_strlist (false), m_strlist (),
        line_xoffset (0), m_ymin (0), m_ymax (0), m_deltax (0),
        m_max_fontsize (0), m_antialias (true)
    { }

    // No copying!

    ft_text_renderer (const ft_text_renderer&) = delete;

    ft_text_renderer& operator = (const ft_text_renderer&) = delete;

    ~ft_text_renderer (void) = default;

    void visit (text_element_string& e);

    void visit (text_element_list& e);

    void visit (text_element_subscript& e);

    void visit (text_element_superscript& e);

    void visit (text_element_color& e);

    void visit (text_element_fontsize& e);

    void visit (text_element_fontname& e);

    void visit (text_element_fontstyle& e);

    void visit (text_element_symbol& e);

    void visit (text_element_combined& e);

    void reset (void);

    uint8NDArray get_pixels (void) const { return pixels; }

    Matrix get_boundingbox (void) const { return bbox; }

    uint8NDArray render (text_element *elt, Matrix& box,
                         int rotation = ROTATION_0);

    Matrix get_extent (text_element *elt, double rotation = 0.0);
    Matrix get_extent (const std::string& txt, double rotation,
                       const caseless_str& interpreter);

    void set_anti_aliasing (bool val) { m_antialias = val; };

    void set_font (const std::string& name, const std::string& weight,
                   const std::string& angle, double size);

    octave_map get_system_fonts (void);

    void set_color (const Matrix& c);

    void set_mode (int m);

    void text_to_pixels (const std::string& txt,
                         uint8NDArray& pxls, Matrix& bbox,
                         int halign, int valign, double rotation,
                         const caseless_str& interpreter,
                         bool handle_rotation);

  private:

    int rotation_to_mode (double rotation) const;

    // Class to hold information about fonts and a strong
    // reference to the font objects loaded by FreeType.

    class ft_font : public text_renderer::font
    {
    public:

      ft_font (void)
        : text_renderer::font (), face (nullptr) { }

      ft_font (const std::string& nm, const std::string& wt,
               const std::string& ang, double sz, FT_Face f = nullptr)
        : text_renderer::font (nm, wt, ang, sz), face (f)
      { }

      ft_font (const ft_font& ft);

      ~ft_font (void)
      {
        if (face)
          FT_Done_Face (face);
      }

      ft_font& operator = (const ft_font& ft);

      bool is_valid (void) const { return get_face (); }

      FT_Face get_face (void) const;

    private:

      mutable FT_Face face;
    };

    void push_new_line (void);

    void update_line_bbox (void);

    void compute_bbox (void);

    int compute_line_xoffset (const Matrix& lb) const;

    FT_UInt process_character (FT_ULong code, FT_UInt previous = 0);

  public:

    void text_to_strlist (const std::string& txt,
                          std::list<text_renderer::string>& lst, Matrix& bbox,
                          int halign, int valign, double rotation,
                          const caseless_str& interp);

  private:

    // The current font used by the renderer.
    ft_font font;

    // Used to stored the bounding box corresponding to the rendered text.
    // The bounding box has the form [x, y, w, h] where x and y represent the
    // coordinates of the bottom left corner relative to the anchor point of
    // the text (== start of text on the baseline).  Due to font descent or
    // multiple lines, the value y is usually negative.
    Matrix bbox;

    // Used to stored the rendered text.  It's a 3D matrix with size MxNx4
    // where M and N are the width and height of the bounding box.
    uint8NDArray pixels;

    // Used to store the bounding box of each line.  This is used to layout
    // multiline text properly.
    std::list<Matrix> line_bbox;

    // The current horizontal alignment.  This is used to align multi-line text.
    int halign;

    // The X offset for the next glyph.
    int xoffset;

    // The Y offset of the baseline for the current line.
    int line_yoffset;

    // The Y offset of the baseline for the next glyph.  The offset is relative
    // to line_yoffset.  The total Y offset is computed with:
    // line_yoffset + yoffset.
    int yoffset;

    // The current mode of the rendering process (box computing or rendering).
    int mode;

    // The base color of the rendered text.
    uint8NDArray color;

    // A list of parsed strings to be used for printing.
    bool m_do_strlist;
    std::list<text_renderer::string> m_strlist;

    // The X offset of the baseline for the current line.
    int line_xoffset;

    // Min and max y coordinates of all glyphs in a line.
    FT_Pos m_ymin;
    FT_Pos m_ymax;

    // Difference between the advance and the actual extent of the latest glyph
    FT_Pos m_deltax;

    // Used for computing the distance between lines.
    double m_max_fontsize;

    // Anti-aliasing.
    bool m_antialias;

  };

  void
  ft_text_renderer::set_font (const std::string& name,
                              const std::string& weight,
                              const std::string& angle, double size)
  {
    // FIXME: take "fontunits" into account
    font = ft_font (name, weight, angle, size, nullptr);
  }

  octave_map
  ft_text_renderer::get_system_fonts (void)
  {
    return ft_manager::get_system_fonts ();
  }

  void
  ft_text_renderer::push_new_line (void)
  {
    switch (mode)
      {
      case MODE_BBOX:
        {
          // Create a new bbox entry based on the current font.

          FT_Face face = font.get_face ();

          if (face)
            {
              Matrix bb (1, 5, 0.0);

              line_bbox.push_back (bb);

              xoffset = yoffset = 0;
              m_ymin = m_ymax = m_deltax = 0;
            }
        }
        break;

      case MODE_RENDER:
        {
          // Move to the next line bbox, adjust xoffset based on alignment
          // and yoffset based on the old and new line bbox.

          Matrix old_bbox = line_bbox.front ();
          line_bbox.pop_front ();
          Matrix new_bbox = line_bbox.front ();

          xoffset = line_xoffset = compute_line_xoffset (new_bbox);
          line_yoffset -= (-old_bbox(1) + math::round (0.4 * m_max_fontsize)
                           + (new_bbox(3) + new_bbox(1)));
          yoffset = 0;
          m_ymin = m_ymax = m_deltax = 0;
        }
        break;
      }
  }

  int
  ft_text_renderer::compute_line_xoffset (const Matrix& lb) const
  {
    if (! bbox.isempty ())
      {
        switch (halign)
          {
          case 0:
            return 0;
          case 1:
            return (bbox(2) - lb(2)) / 2;
          case 2:
            return (bbox(2) - lb(2));
          }
      }

    return 0;
  }

  void
  ft_text_renderer::compute_bbox (void)
  {
    // Stack the various line bbox together and compute the final
    // bounding box for the entire text string.

    bbox = Matrix ();

    switch (line_bbox.size ())
      {
      case 0:
        break;

      case 1:
        bbox = line_bbox.front ().extract (0, 0, 0, 3);
        break;

      default:
        for (const auto& lbox : line_bbox)
          {
            if (bbox.isempty ())
              bbox = lbox.extract (0, 0, 0, 3);
            else
              {
                double delta = math::round (0.4 * m_max_fontsize) + lbox(3);
                bbox(1) -= delta;
                bbox(3) += delta;
                bbox(2) = math::max (bbox(2), lbox(2));
              }
          }
        break;
      }
  }

  void
  ft_text_renderer::update_line_bbox (void)
  {
    // Called after a font change, when in MODE_BBOX mode, to update the
    // current line bbox with the new font metrics.  This also includes the
    // current yoffset, that is the offset of the current glyph's baseline
    // the line's baseline.

    if (mode == MODE_BBOX)
      {
        Matrix& bb = line_bbox.back ();
        bb(1) = m_ymin;
        // Add one pixel to the bbox height to avoid occasional text clipping.
        // See bug #55328.
        bb(3) = (m_ymax + 1) - m_ymin;
        if (m_deltax > 0)
          bb(2) += m_deltax;
      }
  }

  void
  ft_text_renderer::set_mode (int m)
  {
    mode = m;

    switch (mode)
      {
      case MODE_BBOX:
        xoffset = line_yoffset = yoffset = 0;
        m_max_fontsize = 0.0;
        bbox = Matrix (1, 4, 0.0);
        line_bbox.clear ();
        push_new_line ();
        break;

      case MODE_RENDER:
        if (bbox.numel () != 4)
          {
            ::error ("ft_text_renderer: invalid bounding box, cannot render");

            xoffset = line_yoffset = yoffset = 0;
            pixels = uint8NDArray ();
          }
        else
          {
            dim_vector d (4, octave_idx_type (bbox(2)),
                          octave_idx_type (bbox(3)));
            pixels = uint8NDArray (d, static_cast<uint8_t> (0));
            xoffset = compute_line_xoffset (line_bbox.front ());
            line_yoffset = -bbox(1);
            yoffset = 0;
          }
        break;

      default:
        error ("ft_text_renderer: invalid mode '%d'", mode);
        break;
      }
  }
  bool is_opaque (const FT_GlyphSlot &glyph, const int x, const int y)
  {
    // Borrowed from https://stackoverflow.com/questions/14800827/
    //    indexing-pixels-in-a-monochrome-freetype-glyph-buffer
    int pitch = std::abs (glyph->bitmap.pitch);
    unsigned char *row = &glyph->bitmap.buffer[pitch * y];
    char cvalue = row[x >> 3];

    return ((cvalue & (128 >> (x & 7))) != 0);
  }

  FT_UInt
  ft_text_renderer::process_character (FT_ULong code, FT_UInt previous)
  {
    FT_Face face = font.get_face ();
    FT_UInt glyph_index = 0;

    if (face)
      {
        glyph_index = FT_Get_Char_Index (face, code);

        if (code != '\n' && code != '\t'
            && (! glyph_index
                || FT_Load_Glyph (face, glyph_index, FT_LOAD_DEFAULT)))
          {
            glyph_index = 0;
            warn_missing_glyph (code);
          }
        else if ((code == '\n') || (code == '\t'))
          {
            glyph_index = FT_Get_Char_Index (face, ' ');
            if (! glyph_index
                || FT_Load_Glyph (face, glyph_index, FT_LOAD_DEFAULT))
              {
                glyph_index = 0;
                warn_missing_glyph (' ');
              }
            else if (code == '\n')
              push_new_line ();
            else
              {
                // Advance to next multiple of 4 times the width of the "space"
                // character.
                int x_tab = 4 * (face->glyph->advance.x >> 6);
                xoffset = (1 + std::floor (1. * xoffset / x_tab)) * x_tab;
              }
          }
        else
          {
            switch (mode)
              {
              case MODE_RENDER:
                if (FT_Render_Glyph (face->glyph, (m_antialias
                                                   ? FT_RENDER_MODE_NORMAL
                                                   : FT_RENDER_MODE_MONO)))
                  {
                    glyph_index = 0;
                    warn_glyph_render (code);
                  }
                else
                  {
                    FT_Bitmap& bitmap = face->glyph->bitmap;
                    int x0, y0;

                    if (previous)
                      {
                        FT_Vector delta;

                        FT_Get_Kerning (face, previous, glyph_index,
                                        FT_KERNING_DEFAULT, &delta);
                        xoffset += (delta.x >> 6);
                      }

                    x0 = xoffset + face->glyph->bitmap_left;
                    y0 = line_yoffset + yoffset + (face->glyph->bitmap_top - 1);

                    // 'w' seems to have a negative -1
                    // face->glyph->bitmap_left, this is so we don't index out
                    // of bound, and assumes we've allocated the right amount of
                    // horizontal space in the bbox.
                    if (x0 < 0)
                      x0 = 0;

                    for (int r = 0; static_cast<unsigned int> (r) < bitmap.rows; r++)
                      for (int c = 0; static_cast<unsigned int> (c) < bitmap.width; c++)
                        {
                          unsigned char pix
                            = (m_antialias
                               ? bitmap.buffer[r*bitmap.width+c]
                               : (is_opaque (face->glyph, c, r) ? 255 : 0));

                          if (x0+c < 0 || x0+c >= pixels.dim2 ()
                              || y0-r < 0 || y0-r >= pixels.dim3 ())
                            {
                              // ::warning ("ft_text_renderer: x %d,  y %d",
                              //            x0+c, y0-r);
                            }
                          else if (pixels(3, x0+c, y0-r).value () == 0)
                            {
                              pixels(0, x0+c, y0-r) = color(0);
                              pixels(1, x0+c, y0-r) = color(1);
                              pixels(2, x0+c, y0-r) = color(2);
                              pixels(3, x0+c, y0-r) = pix;
                            }
                        }

                    xoffset += (face->glyph->advance.x >> 6);
                  }
                break;

              case MODE_BBOX:
                Matrix& bb = line_bbox.back ();

                // If we have a previous glyph, use kerning information.  This
                // usually means moving a bit backward before adding the next
                // glyph.  That is, "delta.x" is usually < 0.
                if (previous)
                  {
                    FT_Vector delta;

                    FT_Get_Kerning (face, previous, glyph_index,
                                    FT_KERNING_DEFAULT, &delta);

                    xoffset += (delta.x >> 6);
                  }

                // Extend current X offset box by the width of the current
                // glyph.  Then extend the line bounding box if necessary.

                xoffset += (face->glyph->advance.x >> 6);
                bb(2) = math::max (bb(2), xoffset);

                // Store the actual bbox vertical coordinates of this character
                FT_Glyph glyph;
                if (FT_Get_Glyph (face->glyph, &glyph))
                  warn_glyph_render (code);
                else
                  {
                    FT_BBox  glyph_bbox;
                    FT_Glyph_Get_CBox (glyph, FT_GLYPH_BBOX_UNSCALED,
                                       &glyph_bbox);
                    m_deltax = (glyph_bbox.xMax - face->glyph->advance.x) >> 6;
                    m_ymin = math::min ((glyph_bbox.yMin >> 6) + yoffset,
                                        m_ymin);
                    m_ymax = math::max ((glyph_bbox.yMax >> 6) + yoffset,
                                        m_ymax);
                    FT_Done_Glyph (glyph);
                    update_line_bbox ();
                  }
                break;
              }
          }
      }

    return glyph_index;
  }

  void
  ft_text_renderer::text_to_strlist (const std::string& txt,
                                     std::list<text_renderer::string>& lst,
                                     Matrix& box,
                                     int ha, int va, double rot,
                                     const caseless_str& interp)
  {
    uint8NDArray pxls;

    // First run text_to_pixels which will also build the string list

    m_strlist = std::list<text_renderer::string> ();

    unwind_protect frame;
    frame.protect_var (m_do_strlist);
    frame.protect_var (m_strlist);
    m_do_strlist = true;

    text_to_pixels (txt, pxls, box, ha, va, rot, interp, false);

    lst = m_strlist;
  }

  void
  ft_text_renderer::visit (text_element_string& e)
  {
    if (font.is_valid ())
      {
        m_max_fontsize = std::max (m_max_fontsize, font.get_size ());
        FT_UInt glyph_index, previous = 0;

        std::string str = e.string_value ();
        const uint8_t *c = reinterpret_cast<const uint8_t *> (str.c_str ());
        uint32_t u32_c;

        std::size_t n = str.size ();
        std::size_t icurr = 0;
        std::size_t ibegin = 0;

        // Initialize a new string
        std::string fname = font.get_face ()->family_name;
        text_renderer::string fs (str, font, xoffset, yoffset);
        std::vector<double> xdata;

        while (n > 0)
          {
            // Retrieve the length and the u32 representation of the current
            // character
            int mblen = octave_u8_strmbtouc_wrapper (&u32_c, c + icurr);
            if (mblen < 1)
              {
                // This is not an UTF-8 character, use a replacement character
                mblen = 1;
                u32_c = 0xFFFD;
              }

            n -= mblen;

            if (m_do_strlist && mode == MODE_RENDER)
              {
                if (u32_c == 10)
                  {
                    // Finish previous string in m_strlist before processing
                    // the newline character
                    fs.set_y (line_yoffset + yoffset);
                    fs.set_color (color);

                    std::string s = str.substr (ibegin, icurr - ibegin);
                    if (! s.empty ())
                      {
                        fs.set_string (s);
                        fs.set_y (line_yoffset + yoffset);
                        fs.set_xdata (xdata);
                        fs.set_family (fname);
                        m_strlist.push_back (fs);
                      }
                  }
                else
                  xdata.push_back (xoffset);
              }

            glyph_index = process_character (u32_c, previous);

            if (u32_c == 10)
              {
                previous = 0;

                if (m_do_strlist && mode == MODE_RENDER)
                  {
                    // Start a new string in m_strlist
                    ibegin = icurr+1;
                    xdata.clear ();
                    fs = text_renderer::string (str.substr (ibegin), font,
                                                line_xoffset, yoffset);
                  }
              }
            else
              previous = glyph_index;

            icurr += mblen;
          }

        if (m_do_strlist && mode == MODE_RENDER && ! fs.get_string ().empty ())
          {
            fs.set_y (line_yoffset + yoffset);
            fs.set_color (color);
            fs.set_xdata (xdata);
            fs.set_family (fname);
            m_strlist.push_back (fs);
          }
      }
  }

  void
  ft_text_renderer::visit (text_element_list& e)
  {
    // Save and restore (after processing the list) the current font and color.

    ft_font saved_font (font);
    uint8NDArray saved_color (color);

    text_processor::visit (e);

    font = saved_font;
    color = saved_color;
  }

  void
  ft_text_renderer::visit (text_element_subscript& e)
  {
    ft_font saved_font (font);
    int saved_line_yoffset = line_yoffset;
    int saved_yoffset = yoffset;

    double sz = font.get_size ();

    // Reducing font size by 70% produces decent results.
    set_font (font.get_name (), font.get_weight (), font.get_angle (),
              std::max (5.0, sz * 0.7));

    if (font.is_valid ())
      {
        // Shifting the baseline by 15% of the font size gives decent results.
        yoffset -= std::ceil (sz * 0.15);

        if (mode == MODE_BBOX)
          update_line_bbox ();
      }

    text_processor::visit (e);

    font = saved_font;
    // If line_yoffset changed, this means we moved to a new line; hence yoffset
    // cannot be restored, because the saved value is not relevant anymore.
    if (line_yoffset == saved_line_yoffset)
      yoffset = saved_yoffset;
  }

  void
  ft_text_renderer::visit (text_element_superscript& e)
  {
    ft_font saved_font (font);
    int saved_line_yoffset = line_yoffset;
    int saved_yoffset = yoffset;

    double sz = font.get_size ();

    // Reducing font size by 70% produces decent results.
    set_font (font.get_name (), font.get_weight (), font.get_angle (),
              std::max (5.0, sz * 0.7));

    if (saved_font.is_valid ())
      {
        // Shifting the baseline by 40% of the font size gives decent results.
        yoffset += std::ceil (sz * 0.4);

        if (mode == MODE_BBOX)
          update_line_bbox ();
      }

    text_processor::visit (e);

    font = saved_font;
    // If line_yoffset changed, this means we moved to a new line; hence yoffset
    // cannot be restored, because the saved value is not relevant anymore.
    if (line_yoffset == saved_line_yoffset)
      yoffset = saved_yoffset;
  }

  void
  ft_text_renderer::visit (text_element_color& e)
  {
    if (mode == MODE_RENDER)
      set_color (e.get_color ());
  }

  void
  ft_text_renderer::visit (text_element_fontsize& e)
  {
    double sz = e.get_fontsize ();

    // FIXME: Matlab documentation says that the font size is expressed
    //        in the text object FontUnit.

    set_font (font.get_name (), font.get_weight (), font.get_angle (), sz);

    if (mode == MODE_BBOX)
      update_line_bbox ();
  }

  void
  ft_text_renderer::visit (text_element_fontname& e)
  {
    set_font (e.get_fontname (), font.get_weight (), font.get_angle (),
              font.get_size ());

    if (mode == MODE_BBOX)
      update_line_bbox ();
  }

  void
  ft_text_renderer::visit (text_element_fontstyle& e)
  {
    switch (e.get_fontstyle ())
      {
      case text_element_fontstyle::normal:
        set_font (font.get_name (), "normal", "normal", font.get_size ());
        break;

      case text_element_fontstyle::bold:
        set_font (font.get_name (), "bold", "normal", font.get_size ());
        break;

      case text_element_fontstyle::italic:
        set_font (font.get_name (), "normal", "italic", font.get_size ());
        break;

      case text_element_fontstyle::oblique:
        set_font (font.get_name (), "normal", "oblique", font.get_size ());
        break;
      }

    if (mode == MODE_BBOX)
      update_line_bbox ();
  }

  void
  ft_text_renderer::visit (text_element_symbol& e)
  {
    uint32_t code = e.get_symbol_code ();

    std::vector<double> xdata (1, xoffset);
    text_renderer::string fs ("-", font, xoffset, yoffset);

    if (code != text_element_symbol::invalid_code && font.is_valid ())
      {
        process_character (code);
        if (m_do_strlist && mode == MODE_RENDER)
          {
            fs.set_code (code);
            fs.set_xdata (xdata);
          }
      }
    else if (font.is_valid ())
      ::warning ("ignoring unknown symbol: %d", e.get_symbol ());

    if (m_do_strlist && mode == MODE_RENDER && fs.get_code ())
      {
        fs.set_y (line_yoffset + yoffset);
        fs.set_color (color);
        fs.set_family (font.get_face ()->family_name);
        m_strlist.push_back (fs);
      }
  }

  void
  ft_text_renderer::visit (text_element_combined& e)
  {
    int saved_xoffset = xoffset;
    int max_xoffset = xoffset;

    for (auto *txt_elt : e)
      {
        xoffset = saved_xoffset;
        txt_elt->accept (*this);
        max_xoffset = math::max (xoffset, max_xoffset);
      }

    xoffset = max_xoffset;
  }

  void
  ft_text_renderer::reset (void)
  {
    set_mode (MODE_BBOX);
    set_color (Matrix (1, 3, 0.0));
    m_strlist = std::list<text_renderer::string> ();
  }

  void
  ft_text_renderer::set_color (const Matrix& c)
  {
    if (c.numel () == 3)
      {
        color(0) = static_cast<uint8_t> (c(0)*255);
        color(1) = static_cast<uint8_t> (c(1)*255);
        color(2) = static_cast<uint8_t> (c(2)*255);
      }
    else
      ::warning ("ft_text_renderer::set_color: invalid color");
  }

  uint8NDArray
  ft_text_renderer::render (text_element *elt, Matrix& box, int rotation)
  {
    set_mode (MODE_BBOX);
    elt->accept (*this);
    compute_bbox ();
    box = bbox;

    set_mode (MODE_RENDER);

    if (pixels.numel () > 0)
      {
        elt->accept (*this);

        switch (rotation)
          {
          case ROTATION_0:
            break;

          case ROTATION_90:
            {
              Array<octave_idx_type> perm (dim_vector (3, 1));
              perm(0) = 0;
              perm(1) = 2;
              perm(2) = 1;
              pixels = pixels.permute (perm);

              Array<idx_vector> idx (dim_vector (3, 1));
              idx(0) = idx_vector (':');
              idx(1) = idx_vector (pixels.dim2 ()-1, -1, -1);
              idx(2) = idx_vector (':');
              pixels = uint8NDArray (pixels.index (idx));
            }
            break;

          case ROTATION_180:
            {
              Array<idx_vector> idx (dim_vector (3, 1));
              idx(0) = idx_vector (':');
              idx(1) = idx_vector (pixels.dim2 ()-1, -1, -1);
              idx(2) = idx_vector (pixels.dim3 ()-1, -1, -1);
              pixels = uint8NDArray (pixels.index (idx));
            }
            break;

          case ROTATION_270:
            {
              Array<octave_idx_type> perm (dim_vector (3, 1));
              perm(0) = 0;
              perm(1) = 2;
              perm(2) = 1;
              pixels = pixels.permute (perm);

              Array<idx_vector> idx (dim_vector (3, 1));
              idx(0) = idx_vector (':');
              idx(1) = idx_vector (':');
              idx(2) = idx_vector (pixels.dim3 ()-1, -1, -1);
              pixels = uint8NDArray (pixels.index (idx));
            }
            break;
          }
      }

    return pixels;
  }

  // Note:
  // x-extent accurately measures width of glyphs.
  // y-extent is overly large because it is measured from baseline-to-baseline.
  // Calling routines, such as ylabel, may need to account for this mismatch.

  Matrix
  ft_text_renderer::get_extent (text_element *elt, double rotation)
  {
    set_mode (MODE_BBOX);
    elt->accept (*this);
    compute_bbox ();

    Matrix extent (1, 2, 0.0);

    switch (rotation_to_mode (rotation))
      {
      case ROTATION_0:
      case ROTATION_180:
        extent(0) = bbox(2);
        extent(1) = bbox(3);
        break;

      case ROTATION_90:
      case ROTATION_270:
        extent(0) = bbox(3);
        extent(1) = bbox(2);
      }

    return extent;
  }

  Matrix
  ft_text_renderer::get_extent (const std::string& txt, double rotation,
                                const caseless_str& interpreter)
  {
    text_element *elt = text_parser::parse (txt, interpreter);
    Matrix extent = get_extent (elt, rotation);
    delete elt;

    return extent;
  }

  int
  ft_text_renderer::rotation_to_mode (double rotation) const
  {
    // Clip rotation to range [0, 360]
    while (rotation < 0)
      rotation += 360.0;
    while (rotation > 360.0)
      rotation -= 360.0;

    if (rotation == 0.0)
      return ROTATION_0;
    else if (rotation == 90.0)
      return ROTATION_90;
    else if (rotation == 180.0)
      return ROTATION_180;
    else if (rotation == 270.0)
      return ROTATION_270;
    else
      return ROTATION_0;
  }

  void
  ft_text_renderer::text_to_pixels (const std::string& txt,
                                    uint8NDArray& pxls, Matrix& box,
                                    int _halign, int valign, double rotation,
                                    const caseless_str& interpreter,
                                    bool handle_rotation)
  {
    int rot_mode = rotation_to_mode (rotation);

    halign = _halign;

    text_element *elt = text_parser::parse (txt, interpreter);
    pxls = render (elt, box, rot_mode);
    delete elt;

    if (pxls.isempty ())
      return;  // nothing to render

    switch (halign)
      {
      case 1:
        box(0) = -box(2)/2;
        break;

      case 2:
        box(0) = -box(2);
        break;

      default:
        box(0) = 0;
        break;
      }

    switch (valign)
      {
      case 1:
        box(1) = -box(3)/2;
        break;

      case 2:
        box(1) = -box(3);
        break;

      case 3:
        break;

      case 4:
        box(1) = -box(3)-box(1);
        break;

      default:
        box(1) = 0;
        break;
      }

    if (handle_rotation)
      {
        switch (rot_mode)
          {
          case ROTATION_90:
            std::swap (box(0), box(1));
            std::swap (box(2), box(3));
            box(0) = -box(0)-box(2);
            break;

          case ROTATION_180:
            box(0) = -box(0)-box(2);
            box(1) = -box(1)-box(3);
            break;

          case ROTATION_270:
            std::swap (box(0), box(1));
            std::swap (box(2), box(3));
            box(1) = -box(1)-box(3);
            break;
          }
      }
  }

  ft_text_renderer::ft_font::ft_font (const ft_font& ft)
    : text_renderer::font (ft), face (nullptr)
  {
#if defined (HAVE_FT_REFERENCE_FACE)
    FT_Face ft_face = ft.get_face ();

    if (ft_face && FT_Reference_Face (ft_face) == 0)
      face = ft_face;
#endif
  }

  ft_text_renderer::ft_font&
  ft_text_renderer::ft_font::operator = (const ft_font& ft)
  {
    if (&ft != this)
      {
        text_renderer::font::operator = (ft);

        if (face)
          {
            FT_Done_Face (face);
            face = nullptr;
          }

#if defined (HAVE_FT_REFERENCE_FACE)
        FT_Face ft_face = ft.get_face ();

        if (ft_face && FT_Reference_Face (ft_face) == 0)
          face = ft_face;
#endif
      }

    return *this;
  }

  FT_Face
  ft_text_renderer::ft_font::get_face (void) const
  {
    if (! face && ! name.empty ())
      {
        face = ft_manager::get_font (name, weight, angle, size);

        if (face)
          {
            if (FT_Set_Char_Size (face, 0, size*64, 0, 0))
              ::warning ("ft_text_renderer: unable to set font size to %g", size);
          }
        else
          ::warning ("ft_text_renderer: unable to load appropriate font");
      }

    return face;
  }
}

#endif

namespace octave
{
  base_text_renderer *
  make_ft_text_renderer (void)
  {
#if defined (HAVE_FREETYPE)
    return new ft_text_renderer ();
#else
    return 0;
#endif
  }
}
