[QGIS-Developer] hasCrsTransformEnabled removed?

[Radim Blazek]

Hi,

I found in http://qgis.org/api/api_break.html:
setCrsTransformEnabled(), hasCrsTransformEnabled(),
hasCrsTransformEnabledChanged() were removed. CRS transformation is
now always enabled.

But in Project Properties CRS there is now "No projection" checkbox
instead of "Enable on the fly reprojection" in QGIS2, so basically the
same, inverted. Which method to use to get 'No projection' state and
which signal is emitted when it is changed?

QgsProject().instance().crs().isValid() or
QgsProject().instance().crs() == NULL?
QgsProject().instance().crsChanged()?

Thanks
Radim