model execution
And use this function to determine in advance dependencies between
child algorithm parameters with expression based values and
which other child algorithms they depend upon.
Contains variables for model parameters, algorithm results for
other child algorithms which are not dependent on the
algorithm.
Allows removal of final pieces of ModelerAlgorithm code
converted to QgsMapLayer objects with the ownership transferred
to the Python caller
This should make it super-easy for PyQGIS scripts to run processing
algorithms and immediately utilise the results, even if they
are memory layers. They call processing.run(), and get a dict of
results back which includes those layers ready for adding to the
current project or doing some other processing or operations
with, and if they don't transfer to ownership off then these
layers will be correctly garbaged collected by Python.
- remove temporary layers from context, delete them as soon as they
are finished with
- directly remove features via data provider, instead of selecting
and using edit buffer
- use native geometry methods for splitting to single features
and removing rings
Since it's safe to evaluate parameters in background threads
now, it's usually going to be ok to evaluate everything in
the processAlgorithm step.
This keeps the algorithm code as simple as possible, and will
make porting faster.
Note that the prepare/postProcess virtual methods still exist
and can be used when an algorithm MUST do setup/cleanup work
in the main thread.
OCD fix: joins are actually being drawn with two lines going
in both directions. This is totally 100% unacceptable, so
this commit fixes it so they are correctly drawn only with one line.
So that multiple input type parameters are correctly handled,
allowing models with child algorithms like merge to correctly
use any combination of static layers/model inputs/child outputs
as their input parameter
