Font Kerning New Style Data (changes)
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Programmer's FontManager Reference Manuals
» Part 8 - Non-kernel input/output?SWI Calls
» The Font Manager?Font_ReadFontMetrics
» Kerning New Style DataSWI Calls
» Font_ReadFontMetrics
» Kerning New Style Data
Kerning New Style Data
Data Format
| Size | Value |
|---|---|
| 256 x4 | Hash table of offsets to first kern pair with this hash value |
| 4 | Offset of end of all pairs |
| 4 | Font Kern Flags (see below) |
| ? | Kern pair data (see below) |
Kern Pair Data
The kern pair data is stored consecutively, in hash function order.
| Standard Data format | ||
|---|---|---|
| Word | Bits | Value |
| 0 | 0-15 | Internal code of first letter of kern pair |
| 0 | 16-31 | Internal code of second letter of kern pair |
| 1 | 0-15 | X offset in 1/1000^th^ em |
| 1 | 16-31 | Y offset in 1/1000^th^ em |
| Compressed Data format (bit 31 set) | ||
|---|---|---|
| Bits | Contents | |
| 0-7 | First character code | |
| 8-15 | Second character code | |
| 16-31 | X or Y offset | |
If bit 31 of the flag word is set, then each kern pair is held in 1 word. This can only happen if all kern pairs apply to the first 256 characters, and kerning is only in one direction.
Kerning Flags
| Bit | Meaning when set |
|---|---|
| 1 | No x offset |
| 2 | No y offset |
| 31 | Specify short kern pairs |
| All other bits reserved | |
Notes
Kerning information is found by hash table lookup, using the functions:
| Value | Function |
|---|---|
| Hash table index | (first letter) EOR (second letter ROR 4) |
Where the rotate happens in 8 bits.
Note that unlike the rest of the values returned by this call, the kerning information in unscaled, and character codes are internal codes. Font_EnumerateCharacters can be used to map external codes to internal codes.
See also
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