typeSize is meant for Exif metadata only
Metadatum::typeSize doesn't make sense for IPTC and XMP tags.
The current implementation of TypeInfo::typeSize gives wrong results if called for an Exif tag with a non-Exif (unknown) type-id.
r1205 introduced the XMP type LangAlt. Because its typesize is set to 1, the regression test for bug 495 now fails. This happens because the typesize of the new XMP type is used to calculate the size of a tag which happens to have Exif type 17.
Updated by Andreas Huggel about 11 years ago
Introduced proper TiffType, which is used in the new Exif parser. All TIFF types (values 0x0000 - 0xffff) are now a reserved subset of Exiv2 types. Type size was not changed, it is a secondary issue, the main problem was that TypeId 17 was an Exiv2 XMP type but also a possible value for a TIFF type.