al_get_font_line_height - Allegro 5 API

       Returns  the  usual  height of a line of text in the specified font.  For bitmap fonts this is simply the
       height of all glyph bitmaps.  For truetype fonts it is whatever the font file specifies.  In  particular,
       some special glyphs may be higher than the height returned here.

       If  the X is the position you specify to draw text, the meaning of ascent and descent and the line height
       is like in the figure below.

              X------------------------
                  /\         |        |
                 /  \        |        |
                /____\       ascent   |
               /      \      |        |
              /        \     |        height
              ----------------        |
                             |        |
                             descent  |
                             |        |
              -------------------------

       al_get_font_line_height - Allegro 5 API

al_get_text_width(3alleg5), al_get_text_dimensions(3alleg5)

Allegro reference manual                                                        al_get_font_line_height(3alleg5)

              #include <allegro5/allegro_font.h>

              int al_get_font_line_height(const ALLEGRO_FONT *f)