Gets the approximate digit width for a font metrics structure.
This is merely a representative value useful, for example, for determining the initial size for a window. Actual digits in text can be wider or narrower than this, though this value is generally somewhat more accurate than the result of get_approximate_char_width for digits.
| this |
a `PangoFontMetrics` structure |
|
the digit width, in Pango units. |