Some filters are fast enough to return results that it's overkill
to run them in a background thread - add a flag to these filters
to allow them to run (blocking) in the main thread instead.
- add a clone() method to filters, and always search using the
clone instead of the original filter
- add a prepare() method to filters, which is always run in the
main thread and can be used to prepare the filter for safe
background execution (e.g. creating feature iterators in advance)
- don't use QtConcurrent to perform searches in background threads,
since it is not safe to use with QObjects
- instead manually create threads and ensure that cloned objects
are always moved to the thread that they will run in, to ensure
that they correctly have thread affinity with the thread in which
they are executed
This is used a lot, yet the current constructor calls the
normalize() method which does a bunch of operations for no
result.
So instead provide a simple optimised null QgsRectangle
constructor and save a lot of cycles.
Refs #17809
This was a missing capability in the processing API - while algorithms
could declare multiple layer input parameters, there was no corresponding
multi-layer output. This meant that algorithms (such as Package Layers,
Vector Split) which create a set of layers which cannot be determined
in advance had no way to pass these generated layers on for further model
processing steps.
It's also useful for algorithms which operate on a specified folder,
processing all layers found there, and allowing these generated
outputs to be utilised in other model steps (e.g. packaging
all of them, merging them, etc)
Since libspatialindex is not thread safe on all platforms, and
have expressed desire to remove the thread safety that they DO
have on remaining platforms, it's safer and easier for us
to manually add locks to QgsSpatialIndex and be gauranteed that
this class is thread safe on all platforms and libspatialindex
versions.
Also improve docs for the class.
Since the underlying libspatialindex is not thread safe
on some platforms (e.g. Windows), manual calls to detach()
must be made if a QgsSpatialIndex is to be accessed across
multiple threads.
Note that for platforms on which libspatialindex is thread
safe, calling detach() has no effect and does not force the
deep copy.
their unique id()
This is used when generating the QgsHelp url for algorithms
attached to the providers.
Implement helpId overrides for the native and 3d providers so
that they return 'qgis' helpIds, meaning that all QGIS processing
algorithm documentation can be kept within the same url path
regardless of which QGIS provider library it sits within.
This also allows us to freely move algorithms from the Python
'qgis' provider to c++ 'native' provider in future releases
without breaking the help URLs.
Fixes#17231
