This somewhat changes the meaning of outputs from processing 2.x.
In 2.x processing outputs were used both as a method of specifying
inputs to algorithms (file paths to destination layers created
by the algorithm) AND pure outputs (such as statistics calculated
by the algorithm).
This is now split. The old input-type-outputs (destination layers)
are now input parameters (since the parameter value IS an input to the
algorithm). To differentiate them from parameters indicating pure
input layers a new "isDestination()" method was added to
QgsProcessingParameterDefinition.
Output definitions are now purely indications of values CREATED
by the algorithms. Suitable candidates are the existing calculated
stats and actual file path/URI of any layers created by the algorithm.
Moving forward we should ensure all algorithms output as much
useful information as possible - e.g. number of features processed,
number of skipped features, count null geometries encountered, etc...
Add an interface method to show the options dialog at a specific
page. This is required since plugins can now embed their options
in the main options dialog, so they may also need a way to
force this dialog to open.
Implement this in processing so that enabling additional providers
works again.
Intended as a registry for the various processing components,
including providers, algorithms and various parameters and outputs.
Currently handles only registration of providers, as a step toward
removing processing's algList (this requires first porting
the algorithm class to c++)
A QgsProcessingRegistry instance is attached to QgsApplication,
and is retrieved by QgsApplication::processingRegistry()
Nothing particularly exciting here yet, but this commit
moves the definition of the provider base class to a c++
QgsProcessingProvider abstract base class.
As part of this some existing python methods were renamed
to make their use clearer and to fit with the QGIS c++
api conventions:
- getName was renamed to id
- getDescription was renamed to name
- getIcon was renamed to icon
These API breaks are documented
Tags are used while searching in the toolbox. This should help with
finding algorithms when the exact name is not known, eg
you could search for "envelope" or "bounds" and find the
'Polygon from Layer Extent' algorithm.
At the moment it's quite hard to discover algorithms which exist
when you don't know what their called and have to instead search
for every possible naming variant which could exist...
Eg, allows you to search "line merge" and find the "Merge lines"
algorithm. Should make it easier for users who don't know the
exact name to find algorithms.
This fixes some design errors (mainly the ModelerUtils class, which is not needed anymore to hold a copy of algs and providers in order to avoid circular dependencies) and removes unused code
