Initial pen position in freetype?

Question

After drawing a glyph with freetype the pen is advanced as follows:

pen.x += face->glyph->advance.x;
pen.y += face->glyph->advance.y;

My question is, how do you set the initial pen position of the first character, relative to the upper left bound of the drawing surface?

{0,0} isn't correct, as it would draw the first line mostly above the top of the drawing surface, and too close to the left bound.

I suspect it is some combination of:

struct FT_FaceRec {
  ...
  FT_BBox           bbox;

  FT_UShort         units_per_EM;
  FT_Short          ascender;
  FT_Short          descender;
  FT_Short          height;

  FT_Short          max_advance_width;
  FT_Short          max_advance_height;
  ...
}

but it isn't very clear.

Answer 1

For the record I ended up using as initial pen position:

pen.x = 0; pen.y = -face->size->metrics.ascender;

This seems to be the appropriate minimal border to the topleft of the origin of the first glyph.

Further, using face->size->metrics.descender past the last baseline (origin of the last glyph), for the bottom border. And using the x pen position after advancing (+= .advance.x) past the origin of the rightmost glyph as the minimal right side border.