How to enable/disable snapping functionality with PyQGIS?

Question

Goal: The snapping functionality should be enabled and disabled.

I use the function setSnapSettingsForLayer. Convenience function to set snap settings per layer. Short Example:

QgsProject.instance().setSnapSettingsForLayer(layer.id(), True, 2, 1, 10, True)

This approach has already been explained in another post: How to enable the snapping for a layer with the tolerance value with python programming

Up to this point everything works. Now we come to the problem. How can I disable the snapping functionality?

If I set the second parameter in the function setSnapSettingsForLayer to False (to enable the layer snapping), then nothing happens. The Snapping remains activated. Even if I change an another parameter e.g. tolerance, also does not change.

So, how can the Snapping be enabled and disabled while editing?

UPDATE:

Despite my answer, the problem is not yet solved. By choosing Settings -> Snapping options you will find the following window

Only when I confirm this window with the 'OK' button, the code in my answer works. Only now the Snapping can be turned off and on during processing. Has anyone any idea?

Answer 1

I seem to have found the problem. In QGIS all layers were initially activated for the Snapping. First I disable any snapping operations. Subsequently, the Snapping is enabled for a few layers.

for item in QgsMapLayerRegistry.instance().mapLayers().values():
    QgsProject.instance().setSnapSettingsForLayer(item.id(), False, 2, 0, 2, True)
    fieldLayer = mapUtils.getLayerByName(agroInstance.dictData['lpisid'])
    backgroundLpisLayer = mapUtils.getLayerByName('LPISe')
    if checked:
        # Convenience function to set snap settings per layer.
        # it defines the snapping options:
        # id : the id of your layer, True : to enable the layer snapping, 2 : options (2: vertex+segment), 0: type of unit on map, 2 : tolerance, true : avoidIntersection)
        QgsProject.instance().setSnapSettingsForLayer(layerA.id(), True, 2, 0, 2, True)
        QgsProject.instance().setSnapSettingsForLayer(layerB.id(), True, 2, 0, 2, True)

The variable 'checked' checks whether a toggle button has been pressed. With this unsightly way I can turn the snapping on and off.

Answer 2

works in QGIS 3, to toggle snapping on/off use

iface.mapCanvas().snappingUtils().toggleEnabled()

https://qgis.org/api/classQgsSnappingUtils.html