text_renderer.h

#ifndef TEXTREN_INCLUDED
#define TEXTREN_INCLUDED

#include <vector>
#include <cstdint>
#include <systemfonts.h>
#include <textshaping.h>


#include "ragg.h"

#include "agg_font_freetype.h"
#include "agg_span_interpolator_linear.h"
#include "agg_image_accessors.h"
#include "agg_span_image_filter_rgba.h"
#include "agg_span_allocator.h"
#include "agg_path_storage.h"

#include "util/agg_color_conv.h"

typedef agg::font_engine_freetype_int32 font_engine_type;
typedef agg::font_cache_manager<font_engine_type> font_manager_type;

/*
 Basic UTF-8 manipulation routines
 by Jeff Bezanson
 placed in the public domain Fall 2005
 
 This code is designed to provide the utilities you need to manipulate
 UTF-8 as an internal string encoding. These functions do not perform the
 error checking normally needed when handling UTF-8 data, so if you happen
 to be from the Unicode Consortium you will want to flay me alive.
 I do this because error checking can be performed at the boundaries (I/O),
 with these routines reserved for higher performance on data known to be
 valid.
 
 Source: https://www.cprogramming.com/tutorial/utf8.c
 
 Modified 2019 by Thomas Lin Pedersen to work with const char*
 */

static const uint32_t offsetsFromUTF8[6] = {
  0x00000000UL, 0x00003080UL, 0x000E2080UL,
  0x03C82080UL, 0xFA082080UL, 0x82082080UL
};

static const char trailingBytesForUTF8[256] = {
  0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
  0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
  0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
  0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
  0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
  0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
  1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,
  2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2, 3,3,3,3,3,3,3,3,4,4,4,4,5,5,5,5
};

/* conversions without error checking
 only works for valid UTF-8, i.e. no 5- or 6-byte sequences
 srcsz = source size in bytes, or -1 if 0-terminated
 sz = dest size in # of wide characters
 
 returns # characters converted
 dest will always be L'\0'-terminated, even if there isn't enough room
 for all the characters.
 if sz = srcsz+1 (i.e. 4*srcsz+4 bytes), there will always be enough space.
 */
static int u8_toucs(uint32_t *dest, int sz, const char *src, int srcsz)
{
  uint32_t ch;
  const char *src_end = src + srcsz;
  int nb;
  int i=0;
  
  while (i < sz-1) {
    nb = trailingBytesForUTF8[(unsigned char)*src];
    if (srcsz == -1) {
      if (*src == 0)
        goto done_toucs;
    }
    else {
      if (src + nb >= src_end)
        goto done_toucs;
    }
    ch = 0;
    switch (nb) {
    /* these fall through deliberately */
    case 5: ch += (unsigned char)*src++; ch <<= 6;
    case 4: ch += (unsigned char)*src++; ch <<= 6;
    case 3: ch += (unsigned char)*src++; ch <<= 6;
    case 2: ch += (unsigned char)*src++; ch <<= 6;
    case 1: ch += (unsigned char)*src++; ch <<= 6;
    case 0: ch += (unsigned char)*src++;
    }
    ch -= offsetsFromUTF8[nb];
    dest[i++] = ch;
  }
  done_toucs:
    dest[i] = 0;
  return i;
}

/*
 End of Basic UTF-8 manipulation routines
 by Jeff Bezanson
*/

class UTF_UCS {
  std::vector<uint32_t> buffer;
  
public:
  UTF_UCS() {
    // Allocate space in buffer
    buffer.resize(1024);
  }
  ~UTF_UCS() {
  }
  uint32_t * convert(const char * string, int &n_conv) {
    int n_bytes = strlen(string) + 1;
    unsigned int max_size = n_bytes * 4;
    if (buffer.size() < max_size) {
      buffer.resize(max_size);
    }
    
    n_conv = u8_toucs(buffer.data(), max_size, string, -1);
    
    return buffer.data();
  }
};

template<typename PIXFMT>
class TextRenderer {
  UTF_UCS converter;
  FontSettings last_font;
  agg::glyph_rendering last_gren;
  std::vector<textshaping::Point> loc_buffer;
  std::vector<uint32_t> id_buffer;
  std::vector<int> cluster_buffer;
  std::vector<unsigned int> font_buffer;
  std::vector<FontSettings> fallback_buffer;
  std::vector<double> scaling_buffer;
  double current_font_height;
  double current_font_size;
  bool no_bearings;
  
public:
  TextRenderer() :
    converter()
  {
    last_gren = agg::glyph_ren_native_mono;
    get_engine().hinting(true);
    get_engine().flip_y(true);
    get_engine().gamma(agg::gamma_power(1.6));
  }
  
  bool load_font(agg::glyph_rendering gren, const char *family, int face, 
                 double size) {
    FontSettings font = get_font_file(family, 
                                      face == 2 || face == 4, 
                                      face == 3 || face == 4,
                                      face == 5);
    current_font_size = size;
    if (!load_font_from_file(font, gren, size)) {
      Rf_warning("Unable to load font: %s", family);
      current_font_height = 0;
      return false;
    }
    current_font_height = size;
    no_bearings = false;
#if defined(_WIN32)
    // Windows emojis have weird right bearings
    if (strcmp("Segoe UI Emoji", get_engine().family()) == 0) {
      no_bearings = true;
    }
#endif
    return true;
  }
  
  double get_text_width(const char* string) {
    double width = 0.0;
    int error = textshaping::string_width(
      string, 
      last_font, 
      current_font_size, 
      72.0, 
      no_bearings ? 0 : 1, 
      &width
    );
    if (error) {
      return 0.0;
    }
    return width;
  }
  
  void get_char_metric(int c, double *ascent, double *descent, double *width) {
    unsigned index = get_engine().get_glyph_index(c);
    const agg::glyph_cache* glyph = get_manager().glyph(index);
    if (glyph->data_type == agg::glyph_data_color) {
      double mod = current_font_height / get_engine().height();
      if (c != 77 && glyph) {
        *ascent = mod * (double) -glyph->bounds.y1;
        *descent = mod * (double) glyph->bounds.y2;
        
        *width = mod * glyph->advance_x;
      } else {
        *ascent = mod * get_engine().ascent();
        *descent = mod * get_engine().descent();
        
        *width = mod * get_engine().max_advance();
      }
      
#if defined(__APPLE__)
      // Apple emojis have no descender
      double y_shift = double(glyph->bounds.y1 - glyph->bounds.y2) * 0.1;
      *descent += y_shift;
      *ascent += y_shift;
#endif
      
    } else if (glyph && !(c == 77 && index == 0)) { // Only use 77 glyph if found
      *ascent = (double) -glyph->bounds.y1;
      *descent = (double) glyph->bounds.y2;
      
      *width = glyph->advance_x;
    } else {
      // Use global font metrics
      *ascent = get_engine().ascent();
      *descent = get_engine().descent();
      
      *width = get_engine().max_advance();
    }
  }
  
  template<typename renderer_solid, typename renderer>
  void plot_text(double x, double y, const char *string, double rot, double hadj, 
                 renderer_solid &ren_solid, renderer &ren) {
    agg::scanline_u8 sl;
    agg::rasterizer_scanline_aa<> ras;
    agg::conv_curve<font_manager_type::path_adaptor_type> curves(get_manager().path_adaptor());
    curves.approximation_scale(2.0);
    
    double width = get_text_width(string);
    
    if (width == 0.0) {
      return;
    }
    
    int expected_max = strlen(string) * 16;
    loc_buffer.reserve(expected_max);
    id_buffer.reserve(expected_max);
    cluster_buffer.reserve(expected_max);
    font_buffer.reserve(expected_max);
    fallback_buffer.reserve(expected_max);
    scaling_buffer.reserve(expected_max);
    
    int err = textshaping::string_shape(
      string,
      last_font,
      current_font_size, 
      72.0,
      loc_buffer,
      id_buffer,
      cluster_buffer,
      font_buffer,
      fallback_buffer,
      scaling_buffer
    );
    
    if (err != 0) {
      Rf_warning("textshaping failed to shape the string");
      return;
    }
    
    int n_glyphs = loc_buffer.size();
    
    if (n_glyphs == 0) {
      return;
    }
    
    if (rot != 0) {
      rot = agg::deg2rad(-rot);
      agg::trans_affine mtx;
      mtx *= agg::trans_affine_rotation(rot);
      get_engine().transform(mtx);
    }
    
    double cos_rot = cos(rot);
    double sin_rot = sin(rot);
    
    x -= (width * hadj) * cos_rot;
    y -= (width * hadj) * sin_rot;
    
    // Snap to pixel grid for vertical or horizontal text
    if (fmod(rot, 180) < 1e-6) {
      y = std::round(y);
    } else if (fmod(rot + 90, 180) < 1e-6) {
      x = std::round(x);
    }
    int text_run_start = 0;
    for (int j = 1; j <= n_glyphs; ++j) {
      if (j == n_glyphs || font_buffer[j] != font_buffer[j - 1]) {
        if (fallback_buffer.size() == 0 || // To guard against old textshaping version/solaris mock
            load_font_from_file(fallback_buffer[font_buffer[text_run_start]], last_gren, current_font_size)) {
          for (int i = text_run_start; i < j; ++i) {
            const agg::glyph_cache* glyph = get_manager().glyph(id_buffer[i]);
            if (glyph) {
              double x_offset = loc_buffer[i].x * cos_rot + loc_buffer[i].y * sin_rot;
              double y_offset = loc_buffer[i].y * cos_rot + loc_buffer[i].x * sin_rot;
              get_manager().init_embedded_adaptors(glyph, x + x_offset, y + y_offset);
              switch(glyph->data_type) {
              default: break;
              case agg::glyph_data_gray8:
                agg::render_scanlines(get_manager().gray8_adaptor(), 
                                      get_manager().gray8_scanline(), 
                                      ren_solid);
                break;
                
              case agg::glyph_data_color:
                renderColourGlyph(glyph, x + x_offset, y + y_offset, rot, ren, scaling_buffer[font_buffer[text_run_start]]);
                break;
                
              case agg::glyph_data_outline:
                ras.reset();
                ras.add_path(curves);
                agg::render_scanlines(ras, sl, ren_solid);
                break;
              }
            }
          }
        }
        text_run_start = j;
      }
    }
    
    if (rot != 0) {
      get_engine().transform(agg::trans_affine());
    }
  }

private:
  inline font_engine_type& get_engine() {
    static font_engine_type engine;
    return engine;
  }
  
  inline font_manager_type& get_manager() {
    static font_manager_type manager(get_engine());
    return manager;
  }
  
  FontSettings get_font_file(const char* family, int bold, int italic, 
                             int symbol) {
    const char* fontfamily = family;
    if (symbol) {
#if defined _WIN32
      fontfamily = "Segoe UI Symbol";
#else
      fontfamily = "Symbol";
#endif
    }
    return locate_font_with_features(fontfamily, italic, bold);
  }
  
  bool load_font_from_file(FontSettings font, agg::glyph_rendering gren, double size) {
    if (!(gren == last_gren && 
        font.index == last_font.index &&
        strncmp(font.file, last_font.file, PATH_MAX) == 0)) {
      if (!get_engine().load_font(font.file, font.index, gren)) {
        return false;
      }
      last_gren = gren;
      get_engine().height(size);
    } else if (size != get_engine().height()) {
      get_engine().height(size);
    }
    last_font = font;
    return true;
  } 
  
  template<typename ren>
  void renderColourGlyph(const agg::glyph_cache* glyph, double x, double y, double rot, ren &renderer, double scaling) {
    int w = glyph->bounds.x2 - glyph->bounds.x1;
    int h = glyph->bounds.y1 - glyph->bounds.y2;
    agg::rendering_buffer rbuf(glyph->data, w, h, w * 4);
    
    unsigned char * buffer = new unsigned char[w * h * PIXFMT::pix_width];
    agg::rendering_buffer rbuf_conv(buffer, w, h, w * PIXFMT::pix_width);
    agg::convert<PIXFMT, pixfmt_col_glyph>(&rbuf_conv, &rbuf);
    
    agg::trans_affine img_mtx;
    img_mtx *= agg::trans_affine_translation(0, -glyph->bounds.y1);
    if (scaling > 0) {
      img_mtx *= agg::trans_affine_translation(-double(w)/2, 0);
      img_mtx *= agg::trans_affine_scaling(scaling);
      img_mtx *= agg::trans_affine_translation(scaling * double(w)/2, 0);
    }
#if defined(__APPLE__)
    // Apple emojis have no descender
    if (strcmp("Apple Color Emoji", get_engine().family()) == 0) {
      if (scaling < 0) scaling = 1.0; //shouldn't happen as Apple emojis are not scalable
      img_mtx *= agg::trans_affine_translation(0, scaling * double(h) * 0.12);
    }
#endif
    img_mtx *= agg::trans_affine_rotation(rot);
    img_mtx *= agg::trans_affine_translation(x, y);
    agg::trans_affine src_mtx = img_mtx;
    img_mtx.invert();
    
    typedef agg::span_interpolator_linear<> interpolator_type;
    interpolator_type interpolator(img_mtx);
    
    typedef agg::image_accessor_clone<PIXFMT> img_source_type;
    
    PIXFMT img_pixf(rbuf_conv);
    img_source_type img_src(img_pixf);
    agg::span_allocator<typename PIXFMT::blender_type::color_type> sa;
    agg::rasterizer_scanline_aa<> ras;
    agg::scanline_u8 sl;
    
    agg::path_storage rect;
    rect.remove_all();
    rect.move_to(0, 0);
    rect.line_to(0, h);
    rect.line_to(w, h);
    rect.line_to(w, 0);
    rect.close_polygon();
    agg::conv_transform<agg::path_storage> tr(rect, src_mtx);
    ras.add_path(tr);
    
    if (scaling >= 1 || scaling < 0) {
      typedef agg::span_image_filter_rgba_bilinear<img_source_type, interpolator_type> span_gen_type;
      span_gen_type sg(img_src, interpolator);
      agg::render_scanlines_aa(ras, sl, renderer, sa, sg);
    } else {
      agg::image_filter_bilinear filter_kernel;
      agg::image_filter_lut filter(filter_kernel, true);
      
      typedef agg::span_image_resample_rgba_affine<img_source_type> span_gen_type;
      
      span_gen_type sg(img_src, interpolator, filter);
      sg.blur(1);
      agg::render_scanlines_aa(ras, sl, renderer, sa, sg);
    }
    
    delete [] buffer;
  }
};

#endif