Description
Derive cluster source spans from the next greater distinct supplied UTF-16 cluster index, supporting repeated and reverse-ordered glyph clusters; does not infer graphemes.
A glyph’s advance moves the next placement origin; its ink box describes visible bounds relative to that origin. Ink can overhang the advance, and an unknown box differs from a known empty box. These tools use caller-supplied glyph IDs and metrics, placing a horizontal run by cumulative advances without shaping text.
Derive cluster source spans from the next greater distinct supplied UTF-16 cluster index, supporting repeated and reverse-ordered glyph clusters; does not infer graphemes.
When to use this tool
Use this tool to derive cluster source spans from the next greater distinct supplied UTF-16 cluster index, supporting repeated and reverse-ordered glyph clusters; does not infer graphemes.
How to use the tool and how it works
- Enter clusters, sourceLength using the input definitions below.
- Run the operation. Resolve malformed-input errors before interpreting the result.
- Read result.spans. Interpret signs, units, ordering and null values using the rules below.
Validate cluster indexes from 0 through sourceLength, sort their distinct values, and map each original cluster to [start,next greater distinct cluster). The last distinct cluster ends at sourceLength.1
| Input field | Meaning and units | Accepted input |
|---|---|---|
| clusters | Integer UTF-16 source offsets in glyph order, with the operation’s stated accepted bounds. | Dense list of at most 128 finite numbers, subject to the stated integer/shape rules. |
| sourceLength | Source length in UTF-16 code units, integer 0–8192. | Finite safe integer satisfying the stated bounds. |
| Output field | Interpretation |
|---|---|
| result | Object containing the fields below. |
| result.spans | Input-order half-open {start,end} UTF-16 cluster spans. |
{
"input": {
"clusters": [
2,
0,
2
],
"sourceLength": 4
},
"output": {
"result": {
"spans": [
{
"start": 2,
"end": 4
},
{
"start": 0,
"end": 2
},
{
"start": 2,
"end": 4
}
]
}
}
}Limitations and assumptions
- Spans use UTF-16 offsets; repeated or decreasing clusters are preserved, and missing earlier coverage or grapheme boundaries are not inferred.
- All advances, box coordinates, shifts and positional tolerances must share caller-defined metric units. Signed advances are accepted. Glyph records contain id, advance, integer cluster 0–8192 and box = null or [minX,minY,maxX,maxY] with ordered bounds.
- Every declared top-level input is required and unknown fields are rejected. Ordinary strings are limited to 8,192 UTF-16 code units and lists to 128 entries, with tighter operation-specific bounds where stated. JSON text has bounded nesting and node counts.
- Numeric outputs must be finite and within the absolute safe-integer magnitude; exact larger integers use decimal text. Source positions are zero-based UTF-16 offsets and span ends are exclusive unless a different convention is explicitly stated.
Alternative or Complementary methods
Obtain metrics and cluster mappings from the intended font/shaping system, then inspect the supplied observations. Use actual rendering when hinting, fallback choice or visible pixel extents matter.
References
Similar or alternative tools
- Glyph Cluster Index Audit
Audit supplied integer UTF-16 glyph cluster positions for bounds and decreasing order separately; decreasing clusters may be valid RTL shaping, not automatically corruption.
- Glyph Advance Run Tab Stop Placement
Place glyph-run tab positions at the next strictly greater explicit stop, then repeat a supplied positive interval after the last stop; no text shaping.