pimoroni-pico/libraries/pico_vector/alright_fonts.cpp

#include <cstdint>
#include <math.h>
#include <string.h>
#include <algorithm>
#include <vector>
#include <optional>
#include <map>

#include "alright_fonts.hpp"

using namespace pretty_poly;

namespace alright_fonts {
  /*
    utility functions
  */
  pretty_poly::rect_t measure_character(text_metrics_t &tm, uint16_t codepoint) {
    if(tm.face.glyphs.count(codepoint) == 1) {
      glyph_t glyph = tm.face.glyphs[codepoint];

      return {0, 0, ((glyph.advance * tm.size) / 128), tm.size};
    }

    return {0, 0, 0, 0};
  }

  /*
    render functions
  */

  void render_character(text_metrics_t &tm, uint16_t codepoint, pretty_poly::point_t<int> origin) {
    if(tm.face.glyphs.count(codepoint) == 1) {
      glyph_t glyph = tm.face.glyphs[codepoint];

      // scale is a fixed point 16:16 value, our font data is already scaled to
      // -128..127 so to get the pixel size we want we can just shift the
      // users requested size up one bit
      unsigned scale = tm.size << 9;

      pretty_poly::draw_polygon<int8_t>(glyph.contours, origin, scale);
    }
  }

  template<typename mat_t>
  void render_character(text_metrics_t &tm, uint16_t codepoint, pretty_poly::point_t<int> origin, mat_t transform) {
    if(tm.face.glyphs.count(codepoint) == 1) {
      glyph_t glyph = tm.face.glyphs[codepoint];

      // scale is a fixed point 16:16 value, our font data is already scaled to
      // -128..127 so to get the pixel size we want we can just shift the
      // users requested size up one bit
      unsigned scale = tm.size << 9;

      std::vector<pretty_poly::contour_t<int8_t>> contours;
      contours.reserve(glyph.contours.size());

      unsigned int total_points = 0;
      for(auto i = 0u; i < glyph.contours.size(); i++) {
        total_points += glyph.contours[i].count;;
      }

      point_t<int8_t> *points = (point_t<int8_t> *)malloc(sizeof(point_t<int8_t>) * total_points);

      for(auto i = 0u; i < glyph.contours.size(); i++) {
        const unsigned int count = glyph.contours[i].count;
        for(auto j = 0u; j < count; j++) {
          point_t<float> point(glyph.contours[i].points[j].x, glyph.contours[i].points[j].y);
          point *= transform;
          points[j] = point_t<int8_t>(point.x, point.y);
        }
        contours.emplace_back(points, count);
        points += count;
      }

      pretty_poly::draw_polygon<int8_t>(contours, origin, scale);

      free(contours[0].points);
    }
  }

  template void render_character<pretty_poly::mat3_t>(text_metrics_t &tm, uint16_t codepoint, pretty_poly::point_t<int> origin, pretty_poly::mat3_t transform);
  template void render_character<pretty_poly::mat2_t>(text_metrics_t &tm, uint16_t codepoint, pretty_poly::point_t<int> origin, pretty_poly::mat2_t transform);

  /*
    load functions
  */

  // big endian stream value helpers
  uint16_t  ru16(file_io &ifs) {uint8_t w[2]; ifs.read((char *)w, 2); return w[0] << 8 | w[1];}
  int16_t   rs16(file_io &ifs) {uint8_t w[2]; ifs.read((char *)w, 2); return w[0] << 8 | w[1];}
  uint32_t  ru32(file_io &ifs) {uint8_t dw[4]; ifs.read((char *)dw, 4); return dw[0] << 24 | dw[1] << 16 | dw[2] << 8 | dw[3];}
  uint8_t   ru8(file_io &ifs) {uint8_t w; ifs.read(&w, 1); return w;}
  int8_t    rs8(file_io &ifs) {int8_t w; ifs.read(&w, 1); return w;}

  bool face_t::load(file_io &ifs) {
    char marker[4];
    ifs.read(marker, sizeof(marker));

    // check header magic bytes are present
    if(memcmp(marker, "af!?", 4) != 0) {
      // doesn't start with magic marker
      return false;
    }

    // number of glyphs embedded in font file
    this->glyph_count = ru16(ifs);

    // extract flags and ensure none set
    this->flags = ru16(ifs);
    if(this->flags != 0) {
      // unknown flags set
      return false;
    }

    // extract glyph dictionary
    uint16_t glyph_entry_size = 9;
    uint32_t contour_data_offset = 8 + this->glyph_count * glyph_entry_size;
    for(auto i = 0; i < this->glyph_count; i++) {
      glyph_t g;
      g.codepoint = ru16(ifs);
      g.bounds.x  = rs8(ifs);
      g.bounds.y  = rs8(ifs);
      g.bounds.w  = ru8(ifs);
      g.bounds.h  = ru8(ifs);
      g.advance   = ru8(ifs);

      if(ifs.fail()) {
        // could not read glyph dictionary entry
        return false;
      }

      // allocate space for the contour data and read it from the font file
      uint16_t contour_data_length = ru16(ifs);

      // remember where we are in the dictionary
      int pos = ifs.tell();

      // read contour data
      ifs.seek(contour_data_offset);
      while(true) {
        // get number of points in contour
        uint16_t count = ru16(ifs);

        // if count is zero then this is the end of contour marker
        if(count == 0) {
          break;
        }

        // allocate space to store point data for contour and read
        // from file
        pretty_poly::point_t<int8_t> *points = new pretty_poly::point_t<int8_t>[count];
        ifs.read((char *)points, count * 2);

        g.contours.push_back({points, count});
      }

      // return back to position in dictionary
      ifs.seek(pos);
      contour_data_offset += contour_data_length;

      if(ifs.fail()) {
        // could not read glyph contour data
        return false;
      }

      this->glyphs[g.codepoint] = g;
    }

    return true;
  }

  bool face_t::load(std::string_view path) {
    file_io ifs(path);
    if(ifs.fail()) {
      // could not open file
      return false;
    }
    return load(ifs);
  }

}