Computes a `PangoLogAttr` for each character in text.
The attrs array must have one `PangoLogAttr` for each position in text; if text contains N
characters, it has N+1 positions, including the last position at the end of the text. text should be an entire paragraph;
logical attributes can't be computed without context (for example you need to see spaces on either side of a word to know the word is a
word).
| text |
text to process. Must be valid UTF-8 |
| length |
length in bytes of |
| level |
embedding level, or -1 if unknown |
| language |
language tag |
| attrs |
array with one `PangoLogAttr` per character in |
| attrs_len |
length of |