if they are unique in the current project
Instead of always using the layer id, which is generally
gibberish and meaningless for users, instead prefer to use
the layer name as an input in the batch processing dialog. This
is done only if the name is unique within the current project's
loaded layers.
This change makes the dialog more user-friendly, but more importantly
it means that autofilling output values based on an input layer
parameter generates more meaningful automatic output file names.
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 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)
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
