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api: record the beam size at the sample, and write it where NXmx puts it

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dataset_settings gains beam_size_x_um and beam_size_y_um, the horizontal and
vertical size of the X-ray beam where it meets the sample. They follow the same
route total_flux takes - OpenAPI, DatasetSettings, the CBOR start message, the
HDF5 master, and back out of a stored file - and nothing consumes them; this is
metadata a beamline can state and a downstream program can read.

NXmx puts this in the application definition rather than the base class: not
NXbeam's extent (rank 2, nP x 2, per scan point, always FWHM of a rectangular
aperture) but NXmx's own incident_beam_size, a recommended rank-1 two-element
array in the order x, y. Both are live and neither is deprecated, so the choice
matters; the MX definition wins in an MX file. Written as one array with a
units attribute of "m", like every other length in the master, so the settings
hold micrometres and FillMessage converts once.

The unit table of ReadLength_m becomes LengthUnitFactor so the array read can
share it: a master written elsewhere may state this in millimetres.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01EFEJG6WBQv8th4UJFNe53N
This commit is contained in:
leonarski_f
2026-09-02 09:59:34 +02:00
co-authored by Claude Opus 5
parent 7890149ad6
commit 8a04773d1d
20 changed files with 253 additions and 10 deletions
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reader/HDF5MetadataSource.cpp
+23 -8
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@@ -197,23 +197,25 @@ std::string ResolveRelativeToMaster(const std::string &directory,
// silent factor of a thousand, so the unit is read rather than assumed. An undeclared unit means
// metres - what every DECTRIS master and everything this system writes means by one. An unknown
// unit is refused rather than guessed at, for the same reason.
float ReadLength_m(HDF5Object &file, const std::string &name) {
HDF5DataSet dataset(file, name);
const float value = dataset.ReadScalar<float>();
float LengthUnitFactor(HDF5DataSet &dataset, const std::string &name) {
if (!dataset.AttrExists("units"))
return value;
return 1.0f;
const std::string units = dataset.ReadAttrStr("units");
if (units == "m")
return value;
return 1.0f;
if (units == "mm")
return value * 1e-3f;
return 1e-3f;
if (units == "um")
return value * 1e-6f;
return 1e-6f;
throw JFJochException(JFJochExceptionCategory::HDF5, name + ": unknown length unit " + units);
}
float ReadLength_m(HDF5Object &file, const std::string &name) {
HDF5DataSet dataset(file, name);
return dataset.ReadScalar<float>() * LengthUnitFactor(dataset, name);
}
// The same value under different names. DECTRIS Eiger firmware 1.x writes detector_distance where
// NXmx says distance, and a file from that era is still what a repository hands you; a Diamond
// master puts the distance one level up, in NXinstrument rather than in NXdetector. The NXmx
@@ -926,6 +928,19 @@ HDF5MetadataSource::OpenResult HDF5MetadataSource::Open(const std::string &filen
total_flux.reset(); // negative value is an "unknown flux" sentinel; treat as absent
dataset->experiment.TotalFlux(total_flux);
// NXmx incident_beam_size is one two-element array in the order x, y; the settings hold
// it as two lengths in micrometres.
if (master_file->Exists("/entry/instrument/beam/incident_beam_size")) {
HDF5DataSet beam_size(*master_file, "/entry/instrument/beam/incident_beam_size");
std::vector<float> size;
beam_size.ReadVector(size);
if (size.size() == 2) {
const float to_um = LengthUnitFactor(beam_size, "incident_beam_size") * 1e6f;
dataset->experiment.BeamSizeX_um(size[0] * to_um);
dataset->experiment.BeamSizeY_um(size[1] * to_um);
}
}
if (master_file->Exists("/entry/azint") && master_file->Exists("/entry/azint/bin_to_q")) {
HDF5DataSet bin_to_q_dataset(*master_file, "/entry/azint/bin_to_q");
HDF5DataSpace bin_to_q_dataspace(bin_to_q_dataset);