Calculating position for FreeType glyph rendering?

Question

I'm trying to render some text using FreeType and OpenGL:

text = "fghjRT-123VWYUGHJ$@%"

And have two questions:

1. Why there are so weird spaces between letters? (what wrong with advance?)
2. How to calculate top position (or origin position)? (there are some space between yellow border and characters. I want to attach it to the top border)

My render code:

/* top left position on screen to render text (yellow border) */
Vector<2> pos = params.rect.left_top();

/* adjust to bottom (how to get correct origin position?) */
pos.y() += font->char_size();

for (char ch : params.text)
{
    /* contains info after freetype FT_LoadGlyph */
    FontChar const* char_info = font->find_char(ch);

    RectF char_rect(
        pos - char_info->bearing(), /* left, top */
        char_info->glyph_rect().size() /* width, height */
    );

    /* convert screen coordinates to OpenGL coordinates */
    RectF dr = calc_coord(m_screen_size, char_rect);

    /* pack position of glyph and it's texture from bitmap
     * into one sequence of data
     */
    Vector<16> spr_coords = pack_spr_info(dr, char_info->rect());

    m_sprite_buffer.push_back(spr_coords);

    /* move pen by advance */
    pos.x() += char_info->advance();
}

Piece of my glyph loading code:

FT_GlyphSlot slot = face->glyph;

char_info->bearing() = {
    slot->metrics.horiBearingX / 64.0f,
    slot->metrics.horiBearingY / 64.0f
};

char_info->glyph_rect() = { 
    slot->metrics.horiBearingX / 64.0f, /* left */
    slot->metrics.horiBearingY / 64.0f, /* top */
    slot->metrics.width / 64.0f, /* width */
    slot->metrics.height / 64.0f /* height */
};

char_info->advance() = slot->metrics.horiAdvance / 64.0f;

Answer 1

Ok, I found out the answer by myself.
There are was a mistake in my calculation for char_rect position. Correct way:

RectF char_rect(
    pos.x() + char_info->bearing().x(), /* left */
    pos.y() - char_info->bearing().y(), /* top */
    char_info->glyph_rect().size() /* width, height */
);

And the way to find baseline(origin) adjusted from top border:

Vector<2> pos = params.rect.left_top();
pos.y() += font->ascend(); /* move pen down on the screen */

Where:

FT_Face face = ...;
font->ascend() = face->ascender / 32;