| Value | Meaning |
|---|---|
| MONOTONE_GRAPHEMES0 | Return cluster values grouped by graphemes into monotone order. |
| MONOTONE_CHARACTERS1 | Return cluster values grouped into monotone order. |
| CHARACTERS2 | Don't group cluster values. |
| DEFAULT0 | Default cluster level, equal to @HB_BUFFER_CLUSTER_LEVEL_MONOTONE_GRAPHEMES. |
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Data type for holding HarfBuzz's clustering behavior options. The cluster level dictates one aspect of how HarfBuzz will treat non-base characters during shaping.
In @HB_BUFFER_CLUSTER_LEVEL_MONOTONE_GRAPHEMES, non-base characters are merged into the cluster of the base character that precedes them.
In @HB_BUFFER_CLUSTER_LEVEL_MONOTONE_CHARACTERS, non-base characters are initially assigned their own cluster values, which are not merged into preceding base clusters. This allows HarfBuzz to perform additional operations like reorder sequences of adjacent marks.
@HB_BUFFER_CLUSTER_LEVEL_MONOTONE_GRAPHEMES is the default, because it maintains backward compatibility with older versions of HarfBuzz. New client programs that do not need to maintain such backward compatibility are recommended to use @HB_BUFFER_CLUSTER_LEVEL_MONOTONE_CHARACTERS instead of the default.