UCKeyCharSeq

Declaration

typealias UCKeyCharSeq = UInt16

Discussion

The Unicode keyboard-layout ( 'uchr') resource contains the data necessary to map virtual key codes to Unicode character codes for a given keyboard layout. The 'uchr' format consists of a header information section and five key mapping data sections. The UCKeyCharSeq type is a 16-bit value used in the third key mapping section of the 'uchr' resource to specify the output of a dead-key state.

Specifically, the dead-key state record—a structure of type UCKeyStateRecord —uses a UCKeyCharSeq value to contain the character output that results from the resolution of a given dead-key state. You can use a UCKeyCharSeq value in a dead-key state record to represent either an index to a Unicode character sequence or a single Unicode character. The UCKeyCharSeq type is similar to the type UCKeyOutput , but does not itself support indices into dead-key state records.

The interpretation of UCKeyCharSeq depends on bits 15 and 14.

If they are 10 (that is, for values in the range of 0x8000–0xBFFF), then bits 0–13 are an index into the charSequenceOffsets[ field of a structure of type UCKeySequenceDataIndex , which contains offsets to a separate resource-wide list of Unicode character sequences. If a UCKeySequenceDataIndex structure is not present in the resource or the index is beyond the end of the list, then the entire value (that is, bits 0–15) is a single Unicode character to emit. Otherwise (for values in the range of 0x0000–0x7FFF and 0xC000–0xFFFD), bits 0–15 are a single Unicode character, with the exception that a value of 0xFFFE–0xFFFF means no character output (these are invalid Unicode codes).