to handle creation of parameter definition widgets
Previously, these configuration widgets were all hardcoded into the Python modeler
dialog. This prevented 3rd party, plugin provided, parameters from ever being full
first class citizens in QGIS, as there was no way to allow their use as inputs to
user created models to be customised.
Now, the registry is responsible for creating the configuration widget, allowing
for 3rd party parameter types to provide their own customised configuration
widgets.
Refs #26493
This adds a new parameter type specifically for map scales,
QgsProcessingParameterScale. The values are evaluated using
self.parameterAsDouble, which returns the map scale
denominator (matching the standard in other parts of the
QGIS API).
Scale parameters are displayed to users using the standard
QgsScaleWidget, which includes the combo box of predefined
scales and a shortcut button to match the current map scale.
- fix parameter can get converted to plain number parameter after edits
- allow parameter to be linked to parent parameters, so that the
correct distance unit and choices are shown for the parameter
This is a subclass of QgsProcessingParameterNumber, but specifically
for numeric parameters which represent distances. It is linked
to a parent parameter, from which the distance unit will
be determined, and is shown using a dedicated distance widget
within the processing parameters panel. This widget shows
the distance unit.
This avoids the confusion when running algorithms which
use distances where the unit depends on a layer or CRS parameter -
e.g. the distance parameter in the buffer algorithm gives
the distance in layer units... so now we can show those units
directly within the dialog. Hopefully this leads to less
user confusion and accidental "1000 degree buffers"!
Additionally - if the unit is in degrees, a small warning
icon is shown next to the parameter. The tooltip for this
icon advises users to reproject data into a suitable
projected local coordinate system.
Initially implemented for the native buffer and single
sided buffer algorithm only - but more will be added.
Fixes#16290
...to help clarify for users what the different input types mean.
Fixes#17671, which is a result of unclear distinction between
the uses of vector features vs vector layer inputs.
Tagged as needs-docs, as it may help with documentation for 3.0
