Fix bg auto calc on link update

docs/imviz/plugins.rst

@@ -128,11 +128,7 @@ an interactively selected region. A typical workflow is as follows:
 4. Select the desired region using the :guilabel:`Subset` dropdown menu.
 5. If you want to subtract background before performing photometry,
    you have the following 3 options. Otherwise if your image is already
-   background subtracted, choose "Manual" and leave the background set at 0.
-   If you change the linking (see :ref:`imviz-link-control`) after you have
-   a background calculated from Annulus or Subset, you need to re-select
-   the aperture or background subset, respectively, to have it properly
-   recalculated:
+   background subtracted, choose "Manual" and leave the background set at 0:
 
   * Manual: Enter the background value in the :guilabel:`Background value` field.
     This value must be in the same unit as display data, if applicable.

jdaviz/configs/imviz/helper.py

@@ -500,10 +500,6 @@ def link_image_data(app, link_type='pixels', wcs_fallback_scheme='pixels', wcs_u
     if update_plugin and 'imviz-links-control' in [item['name'] for item in app.state.tray_items]:
         link_plugin = app.get_tray_item_from_name('imviz-links-control')
         link_plugin.linking_in_progress = True
-        app.hub.broadcast(LinkUpdatedMessage(link_type,
-                                             wcs_fallback_scheme == 'pixels',
-                                             wcs_use_affine,
-                                             sender=app))
     else:
         link_plugin = None
 
@@ -573,5 +569,10 @@ def link_image_data(app, link_type='pixels', wcs_fallback_scheme='pixels', wcs_u
             'Images successfully relinked', color='success', timeout=8000, sender=app))
 
     if link_plugin is not None:
+        # Only broadcast after success.
+        app.hub.broadcast(LinkUpdatedMessage(link_type,
+                                             wcs_fallback_scheme == 'pixels',
+                                             wcs_use_affine,
+                                             sender=app))
         # reset the progress spinner
         link_plugin.linking_in_progress = False

jdaviz/configs/imviz/plugins/aper_phot_simple/aper_phot_simple.py

@@ -21,7 +21,7 @@
 from traitlets import Any, Bool, List, Unicode, observe
 
 from jdaviz.core.custom_traitlets import FloatHandleEmpty
-from jdaviz.core.events import SnackbarMessage
+from jdaviz.core.events import SnackbarMessage, LinkUpdatedMessage
 from jdaviz.core.region_translators import regions2aperture
 from jdaviz.core.registries import tray_registry
 from jdaviz.core.template_mixin import PluginTemplateMixin, DatasetSelectMixin, SubsetSelect
@@ -76,6 +76,7 @@ def __init__(self, *args, **kwargs):
         self._fitted_model_name = 'phot_radial_profile'
 
         self.session.hub.subscribe(self, SubsetUpdateMessage, handler=self._on_subset_update)
+        self.session.hub.subscribe(self, LinkUpdatedMessage, handler=self._on_link_update)
 
     def reset_results(self):
         self.result_available = False
@@ -172,6 +173,13 @@ def _on_subset_update(self, msg):
         elif sbst.label == self.bg_subset_selected and sbst.data.label == self.dataset_selected:
             self._bg_subset_selected_changed()
 
+    def _on_link_update(self, msg):
+        if self.dataset_selected == '' or self.subset_selected == '':
+            return
+
+        # Force background auto-calculation to update when linking has changed.
+        self._bg_subset_selected_changed()
+
     @observe('subset_selected')
     def _subset_selected_changed(self, event={}):
         subset_selected = event.get('new', self.subset_selected)