Description
Budget horizontal ink overhang outside the explicit advance run, using null when no ink boxes are known; no font rendering.
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.
Budget horizontal ink overhang outside the explicit advance run, using null when no ink boxes are known; no font rendering.
When to use this tool
Use this tool to budget horizontal ink overhang outside the explicit advance run, using null when no ink boxes are known; no font rendering.
How to use the tool and how it works
- Enter glyphsJson using the input definitions below. Serialize the JSON text fields in the decoded shape shown below.
- Run the operation. Resolve malformed-input errors before interpreting the result.
- Read result.advance, result.leading, result.trailing. Interpret signs, units, ordering and null values using the rules below.
Sum all advances and place each known box at its cumulative x position. Leading overhang is max(0,−minimum ink x); trailing overhang is max(0,maximum ink x−total advance). Both are null when no boxes are known.1
| Input field | Meaning and units | Accepted input |
|---|---|---|
| glyphsJson | JSON array of {id, advance, cluster, box} glyph records. id is a string; advance is finite and may be signed; cluster is an integer 0–8192; box is null or [minX,minY,maxX,maxY] with ordered finite bounds. | Text, at most 8,192 UTF-16 code units; the stated grammar and narrower limits also apply. |
These decoded examples show the structure of the JSON text fields. Supply each as its corresponding serialized JSON string.
{
"glyphsJson": [
{
"id": "a",
"advance": 4,
"cluster": 0,
"box": [
0,
-1,
3,
2
]
},
{
"id": "b",
"advance": 5,
"cluster": 1,
"box": null
}
]
}| Output field | Interpretation |
|---|---|
| result | Object containing the fields below. |
| result.advance | Sum of supplied signed advances in metric units. |
| result.leading | Nonnegative known-ink overhang before run origin, or null when no boxes are known. |
| result.trailing | Nonnegative known-ink overhang after total advance, or null when no boxes are known. |
{
"input": {
"glyphsJson": "[{\"id\": \"a\", \"advance\": 4, \"cluster\": 0, \"box\": [0, -1, 3, 2]}, {\"id\": \"b\", \"advance\": 5, \"cluster\": 1, \"box\": null}]"
},
"output": {
"result": {
"advance": 9,
"leading": 0,
"trailing": 0
}
}
}Limitations and assumptions
- A null box is unknown ink, so known-box overhangs can understate the full run’s ink extent. Signed advances are accepted.
- 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 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.
- Glyph Advance Scale Transform
Scale explicit glyph advances and known box coordinates by a nonnegative uniform factor; no hinted rasterization or font metric inference.