[Qgis-developer] How to detect whether there is a scale bar on the canvas (not composer)

[Martin Dobias]

Hi Tom

On Thu, Aug 18, 2016 at 7:48 PM, Tom Chadwin <tom.chadwin at nnpa.org.uk> wrote:
> For plot, see title. How do I find out whether a canvas has a scale bar,
> enabled by the user via View > Decorations > Scale Bar > Enable scale bar?
> I've done my usual ineffective search through the API docs, and can't find
> it.

Your search through API docs was effective, there indeed isn't a
dedicated API call for that :-) The information is stored within
project properties and you can read the enabled state like this:

QgsProject.instance().readBoolEntry("ScaleBar", "/Enabled", False)

This will return a tuple (is_enabled, success) where the first value
is the value you are looking for, the second one just tells whether
the reading of the project property was successful.

Hope that helps!

Cheers
Martin