= attributed strings
attribute lengths are rounded to complete unicode codepoints
zero-length attributes are elided
consecutive attributes of the same type and value are merged
overlapping attributes of different types do not split each other
overlapping attributes of the same type but different values do split
empty string is allowed
empty string cannot have attributes
font family names are case-insensitive both in attributes and in descriptors
attributes are unique throughout a Unicode codepoint, not just to UTF-8 bytes
define what "it is an error" means in the case of uiFreeAttribute() and all uiAttributeValue() functions and constructors
does uiAttributeFamily() return a normalized string
should uiNewAttributeBackground() be renamed to uiNewAttributeBackgroundColor() and likewise for the type constant
should underline colors just ignore non-custom component arguments
should any color getter function accept a NULL pointer
what should uiAttributeUnderlineColor() do if the color type isn't Custom but the other pointers are non-NULL
should uiOpenTypeFeaturesGet() accept a NULL value pointer
what happens if uiOpenTypeFeaturesForEach() is given a NULl function pointer
should FeaturesAttribute be changed to OpenTypeFeaturesAttribute and likewise for the type enum
should uiNewFeaturesAttribute() accept NULL
should uiNewFamilyAttribute() accept NULL
it is an error in ForEach too
invalid values for uiDrawTextAlign
empty text layouts have one line
TODO figure out what to do if any field (particularly the font family name) in uiFontDescriptor is unset