get_width
Description:
Computes the logical width of the glyph string.
This can also be computed using [method@Pango.GlyphString.extents]. However, since this only computes the width, it's much faster. This is in 
      fact only a convenience function that computes the sum of geometry.width for each glyph in the this
      .
Parameters:
| this | a `PangoGlyphString` | 
Returns:
| the logical width of the glyph string. |