In the docs the QgsProcessingParameterEnum class is described as
An enum based parameter for processing algorithms, allowing for
selection from predefined values.
As far as I know, the options are passed and evaluated when the parameter is initialized and I don't believe it's possible to update them dynamically based on selections in other parameters.
I think that using a custom widget wrapper is your best option here.
You can use this example as a basis. The custom widget uses a QgsMapLayerComboBox, a QgsFieldComboBox and a QListWidget with some additional functionalities. The list widget is based on a previous answer I posted here.
"""
/***************************************************************************
A QGIS processing algorithm with a custom checkable list widget wrapper
begin : August 2023
copyright : (C) 2023 by Ben Wirf
email : [email protected]
***************************************************************************/
/***************************************************************************
* *
* This program is free software; you can redistribute it and/or modify *
* it under the terms of the GNU General Public License as published by *
* the Free Software Foundation; either version 2 of the License, or *
* (at your option) any later version. *
* *
***************************************************************************/
"""
from processing.gui.wrappers import WidgetWrapper
from qgis.PyQt.QtWidgets import (QWidget, QListWidget, QListWidgetItem,
QLabel, QLineEdit, QGridLayout, QMenu,
QAction)
from qgis.PyQt.QtCore import (QCoreApplication, QVariant, Qt, QEvent)
from qgis.PyQt.QtGui import QCursor
from qgis.core import (QgsProcessingAlgorithm, QgsProcessingParameterMatrix,
QgsMapLayerProxyModel)
from qgis.gui import (QgsMapLayerComboBox, QgsFieldComboBox)
import re
class CustomListWidget(QgsProcessingAlgorithm):
INPUT_PARAMS = 'INPUT_PARAMS'
def __init__(self):
super().__init__()
def name(self):
return "widgetwrapperexample"
def tr(self, text):
return QCoreApplication.translate("widgetwrapperexample", text)
def displayName(self):
return self.tr("Widget wrapper example")
def group(self):
return self.tr("Examples")
def groupId(self):
return "examples"
def shortHelpString(self):
return self.tr("Example script with custom widgets")
def helpUrl(self):
return "https://qgis.org"
def createInstance(self):
return type(self)()
def initAlgorithm(self, config=None):
param = QgsProcessingParameterMatrix(self.INPUT_PARAMS, 'Input parameters')
param.setMetadata({'widget_wrapper': {'class': CheckableListWidget}})
self.addParameter(param)
def processAlgorithm(self, parameters, context, feedback):
user_options = self.parameterAsMatrix(parameters, self.INPUT_PARAMS, context)
input_vector_layer = user_options[0] # QgsVectorLayer object
# Do something with input_vector_layer...
weight_field = user_options[1] # Name (string) of selected field
# Do something with weight_field...
field_values = user_options[2]# list of selected values
# if field_values:
# Do something with field_values...
# Just return the input parameter values for demo purposes
return {'INPUT_LAYER': input_vector_layer,
'INPUT_FIELD': weight_field,
'VALUE_LIST': field_values}
class CheckableListWidget(WidgetWrapper):
def createWidget(self):
self.custom_widget = customParametersWidget()
return self.custom_widget
def value(self):
source_layer = self.custom_widget.get_layer()
source_field = self.custom_widget.get_field()
checked_values = self.custom_widget.get_values()
# cast int/float items back to numeric values if possible
options = [int(v) if v.isdigit() else float(v) if re.match(r'^-?\d+(?:\.\d+)$', v) else str(v) for v in checked_values]
params = [source_layer, source_field, options]
return params
class customParametersWidget(QWidget):
def __init__(self):
super(customParametersWidget, self).__init__()
self.lyr_lbl = QLabel('Input vector layer:')
self.lyr_cb = QgsMapLayerComboBox(self)
self.lyr_cb.setFilters(QgsMapLayerProxyModel.VectorLayer)
self.lyr_cb.layerChanged.connect(self.layer_changed)
self.fld_lbl = QLabel('Select field:')
self.fld_cb = QgsFieldComboBox(self)
self.fld_cb.setLayer(self.lyr_cb.currentLayer())
self.fld_cb.fieldChanged.connect(self.populate_list_widget)
self.val_lbl = QLabel('Select values:')
self.filter_le = QLineEdit(self)
self.filter_le.setPlaceholderText('Type to filter...')
self.filter_le.textChanged.connect(self.filter_items)
self.value_list = QListWidget(self)
self.layout = QGridLayout()
self.layout.addWidget(self.lyr_lbl, 0, 0, 1, 1)
self.layout.addWidget(self.lyr_cb, 0, 1, 1, 3)
self.layout.addWidget(self.fld_lbl, 1, 0, 1, 1)
self.layout.addWidget(self.fld_cb, 1, 1, 1, 3)
self.layout.addWidget(self.val_lbl, 2, 0, 1, 1)
self.layout.addWidget(self.filter_le, 3, 0, 1, 4)
self.layout.addWidget(self.value_list, 4, 0, 1, 4)
self.setLayout(self.layout)
self.populate_list_widget()
self.context_menu = QMenu(self)
self.action_check_all = QAction('Select All', self)
self.action_check_all.triggered.connect(self.select_all)
self.action_uncheck_all = QAction('De-select All', self)
self.action_uncheck_all.triggered.connect(self.deselect_all)
self.context_menu.addAction(self.action_check_all)
self.context_menu.addAction(self.action_uncheck_all)
self.value_list.viewport().installEventFilter(self)
def layer_changed(self, lyr):
self.fld_cb.setLayer(lyr)
self.populate_list_widget()
def eventFilter(self, obj, event):
if event.type() == QEvent.MouseButtonPress and obj == self.value_list.viewport():
if event.button() == Qt.LeftButton:
clicked_item = self.value_list.itemAt(event.pos())
if clicked_item.checkState() == Qt.Checked:
clicked_item.setCheckState(Qt.Unchecked)
else:
clicked_item.setCheckState(Qt.Checked)
elif event.button() == Qt.RightButton:
self.context_menu.exec(QCursor.pos())
return True
return False
def select_all(self):
for i in range(self.value_list.count()):
item = self.value_list.item(i)
if not item.isHidden():
item.setCheckState(Qt.Checked)
def deselect_all(self):
for i in range(self.value_list.count()):
item = self.value_list.item(i)
if not item.isHidden():
item.setCheckState(Qt.Unchecked)
def filter_items(self, filter_txt):
for i in range(self.value_list.count()):
item = self.value_list.item(i)
filter = filter_txt.lower() not in item.text().lower()
self.value_list.setRowHidden(i, filter)
def populate_list_widget(self):
self.value_list.clear()
lyr = self.lyr_cb.currentLayer()
if not lyr:
return
fld_name = self.fld_cb.currentField()
fld_idx = lyr.fields().lookupField(fld_name)
list_items = lyr.uniqueValues(fld_idx)
if list_items:
for i in list_items:
li = QListWidgetItem(str(i))
li.setFlags(li.flags() | Qt.ItemIsUserCheckable | Qt.ItemIsEnabled)
li.setCheckState(Qt.Unchecked)
self.value_list.addItem(li)
self.filter_le.clear()
def get_layer(self):
return self.lyr_cb.currentLayer()
def get_field(self):
return self.fld_cb.currentField()
def get_values(self):
return [self.value_list.item(i).data(0) for i in range(self.value_list.count()) if self.value_list.item(i).checkState() == Qt.Checked]
In the following screenshots I have selected a land systems layer which contains soil and landform fields. I suggest you add this example algorithm to your toolbox and have a play around with it, inspecting the return values to see how it works and how you can adapt it for your case.
