fix(ui): trace waterfall bar geometry — consistent, sub-ms offsets/widths#65
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The trace waterfall positioned each bar's left edge from Date.parse(start_time) (ms-resolution) but sized its width from duration_ms (sub-ms). The two bases desynced, so a bar's right edge didn't map to the span's true end — making widths look jittery on short traces and letting child bars escape their parent's bar. Derive both offset and width from a single epochMicros() that keeps the sub-ms digits our timestamps carry, and compute width as end−start (same basis as the offset). The time→x mapping is now one monotonic function, so parents always enclose children. duration_ms is still shown as the numeric label. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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The trace waterfall positioned each bar's left edge from
Date.parse(start_time)(ms-resolution) but sized its width fromduration_ms(sub-ms). The two bases desynced, so a bar's right edge didn't map to the span's true end — widths looked jittery on short traces and child bars could escape their parent's bar.Fix: derive both offset and width from one
epochMicros()that keeps the sub-ms digits our timestamps carry, and compute width asend − start(same basis as the offset). The time→x mapping is now one monotonic function, so parents always enclose children.duration_msis still shown as the numeric label.(Microsecond precision is the ceiling from the Postgres
timestamptzcolumns; true nanos would need raw-nano columns — separate follow-up if needed.)Verified:
tsc --noEmitclean,vite buildgreen.🤖 Generated with Claude Code