[QGIS-Developer] Load a QgsMeshLayer within a QgsTask... different Threads?

[Richard Duivenvoorde]

Hi,

Having to juggle with rather large/long loading netcdf files, I thought to off load the loading to a QgsTask, so while the netcdf was loaded user could do other things...

But I get "...is run from a different thread than the object  lives in ..." warnings.

In short:

     def run(self) -> bool:
         log.info(f'LOADING... {self.netcdf_file}')
         try:
             self.layer = QgsMeshLayer(self.netcdf_file, 'PythonLoadedMeshLayer',  'mdal')
     ....

BUT: while it looks like all is fine, I get a Qt warning in my messages, and on my terminal I get:

[INFO] (Dummy-1   ) LOADING... /tmp/kees/aoi/aoi1/areaOfInterest1.nc
Warning: fileName (/home/richard/git/qgis/src/core/project/qgsproject.cpp:812) is run from a different thread than the object  lives in [0x5593004f1aa0 vs 0x5592ff7e6440]
Stacktrace (piped through c++filt):
/home/richard/bin/qgis_/master/debug/bin/qgis(+0xe26a)[0x5592fe9ba26a]
/home/richard/bin/qgis_/master/debug/bin/qgis(+0xea29)[0x5592fe9baa29]
/lib/x86_64-linux-gnu/libQt5Core.so.5(+0xc3b50)[0x7fc594ec3b50]
/lib/x86_64-linux-gnu/libQt5Core.so.5(qt_message_output(QtMsgType, QMessageLogContext const&, QString const&)+0xd)[0x7fc594ec50fd]
/lib/x86_64-linux-gnu/libQt5Core.so.5(QDebug::~QDebug()+0x68)[0x7fc594fc6fa8]
/home/richard/bin/qgis_/master/debug/lib/libqgis_core.so.3.29.0(QgsProject::fileName() const+0x267)[0x7fc592f1af2f]
/home/richard/bin/qgis_/master/debug/lib/libqgis_core.so.3.29.0(QgsMapLayer::loadNamedProperty(QString const&, QgsMapLayer::PropertyType, bool&, QFlags<QgsMapLayer::StyleCategory>)+0x752)[0x7fc592a215c0]
/home/richard/bin/qgis_/master/debug/lib/libqgis_core.so.3.29.0(QgsMapLayer::loadNamedStyle(QString const&, bool&, QFlags<QgsMapLayer::StyleCategory>)+0x2b1)[0x7fc592a20b8f]
/home/richard/bin/qgis_/master/debug/lib/libqgis_core.so.3.29.0(QgsMapLayer::loadDefaultStyle(bool&)+0x2dc)[0x7fc592a1f6ec]
/home/richard/bin/qgis_/master/debug/lib/libqgis_core.so.3.29.0(QgsMeshLayer::loadDefaultStyle(bool&)+0x685)[0x7fc5930a84bb]
/home/richard/bin/qgis_/master/debug/lib/libqgis_core.so.3.29.0(QgsMeshLayer::QgsMeshLayer(QString const&, QString const&, QString const&, QgsMeshLayer::LayerOptions const&)+0x2b9)[0x7fc5930a5ab1]
/home/richard/bin/qgis_/master/debug/share/qgis/python/qgis/_core.so(sipQgsMeshLayer::sipQgsMeshLayer(QString const&, QString const&, QString const&, QgsMeshLayer::LayerOptions const&)+0x3b)[0x7fc43040b9c7]
/home/richard/bin/qgis_/master/debug/share/qgis/python/qgis/_core.so(+0x121a0bc)[0x7fc43041a0bc]
/usr/lib/python3/dist-packages/PyQt5/sip.cpython-311-x86_64-linux-gnu.so(+0x19f60)[0x7fc4dc271f60]
/lib/x86_64-linux-gnu/libpython3.11.so.1.0(+0x1e02fe)[0x7fc47a5e02fe]
/lib/x86_64-linux-gnu/libpython3.11.so.1.0(_PyObject_MakeTpCall+0x7d)[0x7fc47a57baed]
/lib/x86_64-linux-gnu/libpython3.11.so.1.0(_PyEval_EvalFrameDefault+0x4a63)[0x7fc47a509c63]
/lib/x86_64-linux-gnu/libpython3.11.so.1.0(+0x26a6da)[0x7fc47a66a6da]
/lib/x86_64-linux-gnu/libpython3.11.so.1.0(+0x17f30c)[0x7fc47a57f30c]
/usr/lib/python3/dist-packages/PyQt5/sip.cpython-311-x86_64-linux-gnu.so(+0x1196c)[0x7fc4dc26996c]
[INFO] (MainThread) finished OK

My Questions:
- should I NOT do this?
- or is the loading/construction of a QgsMeshLayer having pointers to places it should not?

(mmm loading a QgsVectorLayer (shape via ogr) also results in about the same warnings...
so next question: is there another way to load these large netcdf's without blocking QGIS ?)

Thanks for any info.

Regards,

Richard Duivenvoorde