Commit bc3e464b1e8781c0b4bfed1cc63ac3956cecc21f
2025-04-09T12:35:05
keysyms: Fix Unicode handling - `xkb_utf32_to_keysym`: Allow [Unicode noncharacters]. There is no requirement to drop them and this would be the only function of our API doing so. From the Unicode Standard 16.0, section 23.7 “Noncharacters”: > Applications are free to use any of these noncharacter code points > internally. They have no standard interpretation when exchanged > outside the context of internal use. However, they are not illegal > in interchange, nor does their presence cause Unicode text to be > ill-formed. > If a noncharacter is received in open interchange, an application is > not required to interpret it in any way. It is good practice, > however, to recognize it as a noncharacter and to take appropriate > action, such as replacing it with `U+FFFD` REPLACEMENT CHARACTER, > to indicate the problem in the text. The key part is: > an application is not required to interpret it in any way Since we handle the reverse conversion with `xkb_keysym_to_utf32` just fine, I do not see a good motivation to keep this asymmetry. This is the only function with a special case for these code points. - `xkb_keysym_from_name`: - Unicode format `UNNNN`: allow control characters C0 and C1 and use `xkb_utf32_to_keysym` for the conversion when `NNNN < 0x100`, for backward compatibility. - Numeric hexadecimal format `0xNNNN`: *unchanged*. Contrary to the Unicode format, it does not normalize any keysym values in order to enable roundtrip with `xkb_keysym_get_name`. Also added tests to ensure various properties and consistency. Note about *surrogates*: they are valid valid *code points* but invalid Unicode *scalar values*, i.e. they cannot be encoded in any Unicode encoding form (UTF-8, UTF-16, UTF-32). So their corresponding Unicode keysyms are valid, but: - cannot be used as input of `xkb_keysym_to_utf32` nor `xkb_keysym_to_utf8` - cannot result as output of `xkb_utf32_to_keysym`. Otherwise they are valid e.g. in the Unicode keysym notation. [Unicode noncharacters]: https://en.wikipedia.org/wiki/Universal_Character_Set_characters#Noncharacters