Freetype with C++ not loading all glyphs correctly

Question

I'm using FreeType to load the glyph textures, basically using FT_Load_Char to get the texture, then creating an instance of my custom class Character that contains all the metrics and texture for rendering later:

  for (unsigned int c = min; c < max; c++)
  {
    if (FT_Get_Char_Index(faces[faceIndex].second, c) == 0)
      continue;
    if (FT_Load_Char(faces[faceIndex].second, c, FT_LOAD_RENDER))
    {
      cout << "Error: Failed to load Glyph: " << c << endl;
      continue;
    }
    FT_GlyphSlot glyph = faces[faceIndex].second->glyph;
    GLuint texture;
    glGenTextures(1, &texture);
    glBindTexture(GL_TEXTURE_2D, texture);
    glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
    glTexImage2D(GL_TEXTURE_2D, 0, GL_RED, glyph->bitmap.width, glyph->bitmap.rows, 0, GL_RED, GL_UNSIGNED_BYTE, glyph->bitmap.buffer);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);

    Character character;
    character.texture = texture;
    character.bearingX = glyph->bitmap_left;
    character.bearingY = glyph->bitmap_top;
    character.width = glyph->bitmap.width;
    character.height = glyph->bitmap.rows;
    character.advance = glyph->advance.x;

    characters[faceIndex][c] = character;
    count++;
  }

This works correctly for a vast majority of characters, but typing something like asd-=_+123 will produce the following:

So it's not loading some glyphs correctly like +=- , I am using NotoMono-Regular so it obviously has these basic glyphs

Further debugging by printing out the glyph bitmap buffer gives the following for "bad" characters: bitmap buffer of - gives: α α α α α α α α α α

While for "good" characters it's something like: bitmap buffer of 1 gives: 94

So I think the problem is here, but not sure how to fix it

Answer 1

Are you sure the TTF file that your free type library is consuming is complete? Try uploading the TTF file to one of these websites and see if it has issues parsing the characters you are having issues with.

http://mathew-kurian.github.io/CharacterMap/

http://www.glyphrstudio.com/online/

Answer 2

Character character;
character.texture = texture;
character.bearingX = glyph->bitmap_left;
character.bearingY = glyph->bitmap_top;
character.width = glyph->bitmap.width;
character.height = glyph->bitmap.rows;
character.advance = glyph->advance.x;

As it turns out, using unsigned int for the height and int for bearingY is semantically correct, however, there's is arithmetic down the line that goes like

transformation.translation().y() - (ch.height - ch.bearingY) * size * renderer->aspectRatio

where ch.height - ch.bearingY is implicit "promoted" to unsigned int , then implicitly converted to float , as you can guess, if the expected result of ch.height - ch.bearingY is negative bad things will happen. Who decided unsigned int is greater conversion rank anyways....