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
Algorithms and other processing code should use this method
(instead of dataobjects.getLayerFromString) to
retrieve layers from a string, as it considers the processing
context and allows resolving strings to temporarily stored layers.
This permits processing models to function correctly when
intermediate results are stored as memory layers. Subsequent
model algorithms can then access these temporary layers as inputs.
All temporary layers will be removed when the context object
is destroyed after the model algorithm is run.
Also
- simplify and add tests
- remove large memory leak (persistant store of all non-project layers)
- remove broken support for direct loading postgres/virtual layers
by string (Python version was very broken and would never match
a postgres/virtual layer)
* [processing] qgis regular points test
* [processing] qgis shape buffer variable tests
* [processing] qgis create grid lines test
* [processing] qgis convert geometry test
* [processing] qgis extract by location test
* [processing] qgis add field test
* [processing] trying to fix travis failing
* [processing] trying to fix travis failing/2
* trying to fix travis failing/3
* [processing] Add new default option "ProjectCrs" to ParameterCrs
* [processing] RegularPoints tests shouldn't rely on iface
* [processing] Fix regular points test
* [processing] RandmPointsExtent new CRS parameter
* [processing] qgis random point in extent test
* [processing] qgis random point in extent test/2
* [processing] remove qgis random point in extent test
* no output random points in extent test
* remove useless output
These variables take a lot of time to calculate and cause lots of
lengthy hangs in processing. (Eg add some moderately large rasters
to a project, then try to run any processing algorithm and QGIS
will freeze).
The layer extent can already be used in expressions via the
layer_property function, which only evalutes the extent if required
and only for layers it is used for.
The band stats for raster layers should be moved to a
band_statistic function in core which behaves the same way.
This adds a new input type for expression inputs. Expression
inputs can be linked to a parent layer so that the builder
shows the correct fields and layer variables.
It's designed for two use cases:
1. to be used when an algorithm specifically requires an expression,
eg Select by Expression and Extract by Expression.
2. to be potentially used as a replacement input instead of string
or number literals in algorithms. Eg - if the simplify algorithm
tolerance parameter was replaced with an expression paremeter, then
this expression would be evaluated for every feature before
simplifying that feature. It would allow parameters to be calculated
per feature, as opposed to the current approach of calculating
a parameter once before running the algorithm. It would also
mean algorithms like "variable distance buffer" would no longer
be needed, as a single "buffer" algorithm could then be used
for either a fixed distance, field based, or expression based
distance.
