fontFamilyFallback property Null safety
The ordered list of font families to fall back on when a glyph cannot be found in a higher priority font family.
The value provided in fontFamily will act as the preferred/first font family that glyphs are looked for in, followed in order by the font families in fontFamilyFallback. If all font families are exhausted and no match was found, the default platform font family will be used instead.
When fontFamily is null or not provided, the first value in fontFamilyFallback acts as the preferred/first font family. When neither is provided, then the default platform font will be used. Providing an empty list or null for this property is the same as omitting it.
If the font is defined in a package, each font family in the list will be
prefixed with 'packages/package_name/' (e.g. 'packages/cool_fonts/Roboto').
The package name should be provided by the
package argument in the
List<String>? get fontFamilyFallback => _package != null && _fontFamilyFallback != null ? _fontFamilyFallback!.map((String str) => 'packages/$_package/$str').toList() : _fontFamilyFallback;