expose surface brightness units in internal get_display_units method (#…

…3112)

* expose surface brightness units in app._get_display_units

jdaviz/app.py

@@ -52,6 +52,7 @@
 from jdaviz.utils import (SnackbarQueue, alpha_index, data_has_valid_wcs, layer_is_table_data,
                           MultiMaskSubsetState, _wcs_only_label, flux_conversion,
                           spectral_axis_conversion)
+from jdaviz.core.validunits import check_if_unit_is_per_solid_angle
 
 __all__ = ['Application', 'ALL_JDAVIZ_CONFIGS', 'UnitConverterWithSpectral']
 
@@ -1249,14 +1250,29 @@ def _get_display_unit(self, axis):
             if axis == 'spectral':
                 sv = self.get_viewer(self._jdaviz_helper._default_spectrum_viewer_reference_name)
                 return sv.data()[0].spectral_axis.unit
-            elif axis == 'flux':
+            elif axis in ('flux', 'sb', 'spectral_y'):
                 sv = self.get_viewer(self._jdaviz_helper._default_spectrum_viewer_reference_name)
-                return sv.data()[0].flux.unit
+                sv_y_unit = sv.data()[0].flux.unit
+                if axis == 'spectral_y':
+                    return sv_y_unit
+                elif axis == 'flux':
+                    if check_if_unit_is_per_solid_angle(sv_y_unit):
+                        # TODO: this will need updating once solid-angle unit can be non-steradian
+                        return sv_y_unit * u.sr
+                    return sv_y_unit
+                else:
+                    # surface_brightness
+                    if check_if_unit_is_per_solid_angle(sv_y_unit):
+                        return sv_y_unit
+                    return sv_y_unit / u.sr
             else:
                 raise ValueError(f"could not find units for axis='{axis}'")
+        uc = self._jdaviz_helper.plugins.get('Unit Conversion')._obj
+        if axis == 'spectral_y':
+            # translate options from uc.flux_or_sb to the prefix used in uc.??_unit_selected
+            axis = {'Surface Brightness': 'sb', 'Flux': 'flux'}[uc.flux_or_sb_selected]
         try:
-            return getattr(self._jdaviz_helper.plugins.get('Unit Conversion')._obj,
-                           f'{axis}_unit_selected')
+            return getattr(uc, f'{axis}_unit_selected')
         except AttributeError:
             raise ValueError(f"could not find display unit for axis='{axis}'")