gather() staged x as f32 relative to the series' own x0() -- the start of
the whole retained window -- so the quantisation was a fraction of the
ring rather than of the view: 1.9 us at 20 s of retained data, which at a
10 us view across a 716 px axis is over 100 px between where a sample is
drawn and the x a readout quotes for it (crosshair_point() reads x_at()
in exact f64). It halved on every zoom out, which is what made it read as
"zooming in makes the crosshair select a point beside the data".
The origin is now the caller's (plotter c2c8c59): the renderer passes the
visible range's minimum, so the error is a fixed 2^-24 of what is on
screen -- about 4e-5 px over a 700 px axis -- at any zoom. The parameter
sits before out_xy so every call site is a compile error rather than a
silent change of behaviour.
The renderer no longer reads series.x0() at paint time at all, which
removes two of the three symptoms of the torn window_x0_ read by
construction; the ink probe's now-vacuous kept_fixed_x0 walk goes with
them, replaced by a drawn-vs-quoted pixel figure. neighbours() still
tests the visible range against x_at(0), so the cache stays load-bearing.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
The time ring was f32 like the values, holding each stamp relative to an epoch
fixed at the first sample ever seen -- so the number stored grew for as long as
the app ran while the interval it had to resolve stayed one sample period. At
1 MS/s the f32 ULP reaches the sample period after about sixteen seconds, so two
to four consecutive samples rounded onto one stamp after half a minute and eight
after a minute. On screen that is a plateau the LOD envelope draws as a
zero-width segment -- a vertical spike where the waveform should be -- and in an
export it was three distinct diffs at 2, 2.5 and 3 ULP instead of one clock.
A value's precision is a property of the signal; a timestamp's is a property of
how long the scope has been running. Only the clock widens: the values are the
memory budget. That makes the two slices different sizes per slot, so
plan_partition() weighs its growth loop in bytes rather than in slots (and
bytes_for() is what bounds the doubling); live_window_locked() loses the f32
round-trip of its bounds, which existed only to keep a sample sitting exactly on
one; and EventSnapshot::stamps is f64 because a pause view is not rebased and so
carries full stream time.
Verified against the fast mock: np.diff over two million exported rows now holds
exactly one step (1e-06, 1999999 times), no duplicate or backwards stamps, and
the 200 MB ring still spans 8.39 s. Every documented probe assertion unchanged.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
The flicker ("no data" at no constant frequency, worse with the measurements
and cursors panes up) was a torn read of the window's first stamp: acquire()
pins the window to the ring's oldest slot, and reading it at paint time races
the producer lapping it, returning a stamp one ring span too new. x0() is the
origin every trace point is reconstructed from, so one torn read produced a
refused neighbours(), a filter that dropped three quarters of the points, and
a polyline shifted off its axis. It is cached by acquire() under the lock now.
EventSeries::neighbours() answered from the (x - x0)/dx grid, whose drift from
the real arrival stamps arrives as a constant offset in seconds -- a doubling
share of the screen per zoom step, which is the "zooming into a held event
clips it more from the left" report. Both series binary-search the stamps now.
The measurements pane went through the LOD pyramid rather than reading its
window raw (19.7 ms per recompute to 1.2 ms, 0.1% of a 2 M-sample window) and
recomputes on a cadence; the math engine lost a per-slot heap allocation, a
per-sample source lookup by name and a fetch_add that cost more than the
arithmetic it counted.
The cursors pane's mix mode drew a line per *named* slot, so a slot holding a
signal that can never produce a channel -- the stream's timestamp -- got a row
that could only read "--", and such names were re-saved every session. It
counts bound traces now and apply_layout() refuses them.
Four toolbar icons are drawn for this app and compiled in as a GResource: the
stock ones were a record dot for the trigger and three magnifiers for cursors,
measurements and math.
New probes and dump lines for all of it (trace ink, measure cost, math cost,
event zoom, toolbar icons); README and CLAUDE.md record what they cure.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Martino Ferrari