Deactivate Snapping for Measure Maptool (mActionMeasure) in QGIS temporarily

Question

I use the QGIS measure-tool to measure distances. I often would like to deactivate the snapping temporarily while using the measure-tool.

Is it possible to deactivate snapping (for example with a shortcut) while measuring and re-activating is when i digitize again?

Answer 1

We could create a function whereby:

• If the mActionMeasure button is checked, the snapping mode is turned Off
• If the mActionMeasure button is unchecked, the snapping mode is turned On

Here is the function which you can paste into the Python Console (change the parameters to fit your needs, you don't need to change the lines which include proj.setSnapSettingsForLayer(...)):

def snap_func():
    proj = QgsProject.instance()
    layer = qgis.utils.iface.activeLayer()
    if iface.actionMeasure().isChecked():
        proj.writeEntry('Digitizing', 'DefaultSnapType', 'off') 
        proj.setSnapSettingsForLayer(layer.id(), True, 0, 0, 0, True)
    else:
        proj.writeEntry('Digitizing', 'DefaultSnapType', 'to vertex and segment') 
        proj.writeEntry('Digitizing', 'SnappingMode', 'current_layer') 
        proj.writeEntry('Digitizing','DefaultSnapTolerance', 10.0)
        proj.setSnapSettingsForLayer(layer.id(), True, 0, 0, 0, True)

Then type the following to connect the mActionMeasure button to the function:

iface.actionMeasure().toggled.connect(snap_func)

---

Edit:

• To save and restore snapping settings for Current and All visible layers:

  proj = QgsProject.instance()
  # Create dictionary
  snap_options_dict = {}
  def snap_func():
      layer = qgis.utils.iface.activeLayer()  
      if iface.actionMeasure().isChecked():
          # Save current snapping settings        
          snap_options_dict['SnappingMode'] = proj.readEntry('Digitizing','SnappingMode')[0]
          snap_options_dict['DefaultSnapType'] = proj.readEntry('Digitizing','DefaultSnapType')[0]
          snap_options_dict['DefaultSnapTolerance'] = proj.readEntry('Digitizing','DefaultSnapTolerance')[0]
          # Switch snapping off
          proj.writeEntry('Digitizing', 'DefaultSnapType', 'off') 
          proj.writeEntry('Digitizing', 'DefaultSnapTolerance', 0.0) 
          proj.setSnapSettingsForLayer(layer.id(), True, 0, 0, 0, True)
      else:
          # Load snapping settings saved in dictionary
          proj.writeEntry('Digitizing', 'SnappingMode', snap_options_dict['SnappingMode']) 
          proj.writeEntry('Digitizing', 'DefaultSnapType', snap_options_dict['DefaultSnapType'])
          proj.writeEntry('Digitizing','DefaultSnapTolerance', snap_options_dict['DefaultSnapTolerance'])
          proj.setSnapSettingsForLayer(layer.id(), True, 0, 0, 0, True)
  
  iface.actionMeasure().toggled.connect(snap_func)
  

• To save and restore snapping settings for Advanced:

  proj = QgsProject.instance()
  # Create dictionary
  snap_options_dict = {}
  def snap_func():
      if iface.actionMeasure().isChecked():
          for layer in QgsMapLayerRegistry.instance().mapLayers().values():
              # Save current snapping settings        
              snap_options_dict[layer.id()] = proj.snapSettingsForLayer(layer.id())
              # Switch snapping off
              proj.setSnapSettingsForLayer(layer.id(), False, 0, 0, 0, False)
      else:
          for layer in QgsMapLayerRegistry.instance().mapLayers().values():
              # Load snapping settings saved in dictionary
              proj.setSnapSettingsForLayer(layer.id(), \
              snap_options_dict[layer.id()][1], \
              snap_options_dict[layer.id()][2], \
              snap_options_dict[layer.id()][3], \
              snap_options_dict[layer.id()][4], \
              snap_options_dict[layer.id()][5])
  
  iface.actionMeasure().toggled.connect(snap_func)