the index of a line, which must be between 0 and pango_layout_get_line_count(layout) - 1, inclusive.
the requested PangoLayoutLine, or %NULL if the index is out of range. This layout line can be ref'ed and retained, but will become invalid if changes are made to the PangoLayout.
Retrieves a particular line from a PangoLayout.
Use the faster [method@Pango.Layout.get_line_readonly] if you do not plan to modify the contents of the line (glyphs, glyph widths, etc.).