[needs-docs][processing] Add tooltips to input types in modeler

...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

python/plugins/processing/modeler/ModelerDialog.py

@@ -620,6 +620,7 @@ def fillInputsTree(self):
             paramItem.setText(0, paramType)
             paramItem.setIcon(0, icon)
             paramItem.setFlags(Qt.ItemIsEnabled | Qt.ItemIsSelectable | Qt.ItemIsDragEnabled)
+            paramItem.setToolTip(0, ModelerParameterDefinitionDialog.inputTooltip(paramType))
             parametersItem.addChild(paramItem)
         self.inputsTree.addTopLevelItem(parametersItem)
         parametersItem.setExpanded(True)

python/plugins/processing/modeler/ModelerParameterDefinitionDialog.py

@@ -51,7 +51,8 @@
                        QgsProcessingParameterFeatureSource,
                        QgsProcessingParameterBand)
 from qgis.PyQt.QtCore import (Qt,
-                              QByteArray)
+                              QByteArray,
+                              QCoreApplication)
 from qgis.PyQt.QtWidgets import (QDialog,
                                  QVBoxLayout,
                                  QLabel,
@@ -441,3 +442,24 @@ def reject(self):
         settings.setValue("/Processing/modelParametersDefinitionDialogGeometry", self.saveGeometry())
 
         QDialog.reject(self)
+
+    @staticmethod
+    def inputTooltip(input_type):
+        tooltips = {
+            ModelerParameterDefinitionDialog.PARAMETER_NUMBER: QCoreApplication.translate('Processing', 'A numeric parameter, including float or integer values.'),
+            ModelerParameterDefinitionDialog.PARAMETER_RASTER: QCoreApplication.translate('Processing', 'A raster layer parameter.'),
+            ModelerParameterDefinitionDialog.PARAMETER_TABLE: QCoreApplication.translate('Processing', 'A vector layer parameter, e.g. for algorithms which change layer styles, edit layers in place, or other operations which affect an entire layer.'),
+            ModelerParameterDefinitionDialog.PARAMETER_VECTOR: QCoreApplication.translate('Processing', 'A vector feature parameter, e.g. for algorithms which operate on the features within a layer.'),
+            ModelerParameterDefinitionDialog.PARAMETER_STRING: QCoreApplication.translate('Processing', 'A freeform string parameter.'),
+            ModelerParameterDefinitionDialog.PARAMETER_EXPRESSION: QCoreApplication.translate('Processing', 'A QGIS expression parameter, which presents an expression builder widget to users.'),
+            ModelerParameterDefinitionDialog.PARAMETER_BOOLEAN: QCoreApplication.translate('Processing', 'A boolean parameter, for true/false values.'),
+            ModelerParameterDefinitionDialog.PARAMETER_TABLE_FIELD: QCoreApplication.translate('Processing', 'A vector field parameter, for selecting an existing field from a vector source.'),
+            ModelerParameterDefinitionDialog.PARAMETER_EXTENT: QCoreApplication.translate('Processing', 'A map extent parameter.'),
+            ModelerParameterDefinitionDialog.PARAMETER_FILE: QCoreApplication.translate('Processing', 'A file parameter, for use with non-map layer file sources.'),
+            ModelerParameterDefinitionDialog.PARAMETER_POINT: QCoreApplication.translate('Processing', 'A geographic point parameter.'),
+            ModelerParameterDefinitionDialog.PARAMETER_CRS: QCoreApplication.translate('Processing', 'A coordinate reference system (CRS) input parameter.'),
+            ModelerParameterDefinitionDialog.PARAMETER_MULTIPLE: QCoreApplication.translate('Processing', 'An input allowing selection of multiple sources, including multiple map layers or file sources.'),
+            ModelerParameterDefinitionDialog.PARAMETER_BAND: QCoreApplication.translate('Processing', 'A raster band parameter, for selecting an existing band from a raster source.'),
+            ModelerParameterDefinitionDialog.PARAMETER_MAP_LAYER: QCoreApplication.translate('Processing', 'A generic map layer parameter, which accepts either vector or raster layers.')
+        }
+        return tooltips[input_type]