Converts from byte index_ within the this to line and X position.
The X position is measured from the left edge of the line.
| this |
a `PangoLayout` |
| index_ |
the byte index of a grapheme within the layout |
| trailing |
an integer indicating the edge of the grapheme to retrieve the position of. If > 0, the trailing edge of the grapheme, if 0, the leading of the grapheme |
| line |
location to store resulting line index. (which will between 0 and pango_layout_get_line_count(layout) - 1) |
| x_pos |
location to store resulting position within line (pango_scale units per device unit) |