Font_EnumerateCharacters (changes)
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» FontManager
» SWI Calls
» Font_EnumerateCharacters
Font_EnumerateCharacters
(SWI &400A9)
| Entry | |
|---|---|
| R0 | Font handle (0 for current) |
| R1 | Character code (0 to start) |
| Exit | |
|---|---|
| R0 | Corrupted |
| R1 | Next character (-1 if this is the last) |
| R2 | Internal character code of this character (-1 if unmapped) |
Use
This purpose of this call is to determine which characters are present in a font, and which glyphs in the underlying font file characters map to.
Notes
This call works only by looking at encoding files – it cannot guarantee that a given character is actually defined in a font file, but it can return which characters definitely are not, by returning with R2 set to -1.
Examples
For the font \FHomerton.Medium\EUTF8, a call sequence might be:
| Entry | Exit | |
|---|---|---|
| R1 = 0 | R1 = &20 (space) | R2 = -1 |
| R1 = &10F (d-caron) | R1 = &112 (E macron) | R2 = &151 |
| R1 = &112 (E-macron) | R1 = &113 (e macron) | R2 = &185 |
| R1 = &113 (e-macron) | R1 = &116 (E dot) | R2 = &195 |
| R1 = &FB02 (f1 ligature) | R1 = -1 | R2 = &FF |
So, in this example, we see that the f1 ligature character (Unicode FB02) is character &FF within the Homerton.Medium font file.
This call may be of use in conjunction with Font_ReadFontMetrics kerning data. Also, it would allow a character map program to scan through the UCS space to find defined characters.
See also
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