Changing scale bar units to feet in PyQGIS?

Question

I'm trying to change the default QGIS scale bar from meters to feet. From the API documentation it looks like I should be able to use the QgsComposerScaleBar.applyDefaultSize() function.

I thought this would work

scalebar = QgsComposerScaleBar(c)
scalebar.setComposerMap(composerMap)
feet = QgsComposerScaleBar.ScaleBarUnits.Feet
scalebar.applyDefaultSize(feet)
c.addItem(scalebar)

but I get the error

Object::disconnect: No such signal QObject::extentChanged()

Any ideas on how to do this, or what this error means?

I'm using QGIS 2.6.1-Brighton and the CRS for my dataset is EPSG:26917 - NAD83 / UTM zone 17N.

Answer 1

If I got you right, you can define the units of the QGIS scale bar this way:

• Using the GUI:

  Go to Settings->Options->Map Tools->Measure Tool and set Preferred measurement units to Feet.

• Programmatically: Open a QGIS console and copy this:

  from PyQt4.QtCore import QSettings    
  QSettings().setValue("Qgis/measure/displayunits","feet")
  

Answer 2

Thanks for the help @gcarrillo!

As far as I can tell QSettings().setValue("Qgis/measure/displayunits","feet") had no effect, but scalebar.applyDefaultSize(QgsComposerScaleBar.Feet) did the trick.

For prosperity, here's a working example of changing the scale bar to miles.

scalebar = QgsComposerScaleBar(c)
scalebar.setComposerMap(composerMap)
scalebar.applyDefaultSize(QgsComposerScaleBar.Feet)
scalebar.setUnitLabeling("mile")
scalebar.setNumMapUnitsPerScaleBarUnit(5280.0)
scalebar.setNumSegmentsLeft(0)
scalebar.setNumSegments(4)
scalebar.setNumUnitsPerSegment(0.25*5280.0)
c.addItem(scalebar)