Every traffic refresh rebuilt the attributed-string dictionary (font,
color, paragraph style, baseline number, dict) and ran a CoreText layout
via NSAttributedString::size() just to size the status item, although
both depend only on the button height and the glyph advance.
The dictionary and the monospaced per-glyph advance (measured once
through the same layout engine with a "0" probe) are now cached keyed by
button height, and the width is computed as longest-line length times
the advance. The speed charset is pure ASCII on a monospaced font, so
the arithmetic width matched the layout width exactly (max deviation
0.000pt over 2000 realistic samples).
Standalone A/B over 43,200 updates (12h at 1 Hz), same hot path:
| variant | mean | p95 | phys_footprint after |
| --- | ---: | ---: | ---: |
| rebuild + layout (old) | 6.89us | 7.8us | 19.8MB |
| cached attrs | 4.71us | 5.0us | 7.8MB |
| cached + arithmetic width | 0.27us | 0.3us | 6.0MB |
The retained-memory delta is malloc-zone fragmentation from the churn,
which this removes at the source.
Tunglies