slice: refactor plugin to decouple from cube (#2715)

* refactor slice plugin

* allow tool to become default when first becoming visible
* allow downstream to override slice axis
* allow for multiple viewers with indicators by using mixins for WithSliceIndicator or WithSliceSelection
* decouple slice axis from cube and replace with optional "snap to slice" functionality

* initialize original slice location to middle of first found data layer

* re-implement play/increment functionality

* and add decrement since slider no longer exists

* slice indicator: use sci notation only if necessary

* initialize value_unit in cubeviz

* fix jittering indicator

* delay snap to slice while inputting number

* implement deprecated API access to slice

* changelog entry

* update docs

* support test data

* deprecate cubeviz_helper.select_slice

* edge checks and wrapping support in cube play functionality

* update tests

* reproduce previous logic for init slice

* do not allow disabling snapping in cubeviz

* but keep support for downstream

* avoid calls to viewer.data()

* ap phot: determine slice-index on the fly instead of relying on plugin

* update even more tests

* read slice component from x_att

to support wave/wavelength/freq/frequency/wavenumber/velocity/energy

* handle cubes passing int to slice value

* further support for flexible x_att handling

* more test updates

* fix support for slice axis given in integers

* remove comment

* fix play support when slices are integers

* allow initializing when slice axis is pixel

* always label as "value" in UI

* can always change to be more intelligent based on data and x-display-unit later

* don't allow starting playing if no slices

(this would have quite immediately after otherwise, but is hard to reliably test since that is threaded)

* DOC: Use new API in concept notebook

CHANGES.rst

@@ -32,6 +32,9 @@ Cubeviz
 
 - Live previews in spectral extraction plugin. [#2733]
 
+- Slice plugin is refactored to rely on the spectral value instead of the slice index.  This removes
+  both the slider and slice-index input. [#2715]
+
 Imviz
 ^^^^^
 
@@ -67,7 +70,8 @@ Cubeviz
   be removed in a future release. [#2664]
 
 - Slice plugin's ``wavelength``, ``wavelength_unit``, and ``show_wavelength`` are deprecated in favor
-  of ``value``, ``value_unit``, and ``show_value``, respectively. [#2706]
+  of ``value``, ``value_unit``, and ``show_value``, respectively.  ``slice`` is also deprecated
+  and should be replaced with accessing/setting ``value`` directly. [#2706, #2715]
 
 Imviz
 ^^^^^

docs/cubeviz/plugins.rst

@@ -74,10 +74,10 @@ The slice plugin provides the ability to select the slice
 of the cube currently visible in the image viewers, with the
 corresponding wavelength highlighted in the spectrum viewer.
 
-The slider can be grabbed to scrub through the cube.  To choose
-a specific slice, enter a slice number (integer) or an approximate
-wavelength (in which case the nearest slice will be selected and
-the wavelength entry will update to the exact value of that slice).
+To choose a specific slice, enter an approximate wavelength (in which case the nearest slice will 
+be selected and the wavelength entry will "span" to the exact value of that slice).  The snapping
+behavior can be disabled in the plugin settings to allow for smooth scrubbing, in which case the
+closest slice will still be displayed in the cube viewer.
 
 The spectrum viewer also contains a tool to allow clicking and
 dragging in the spectrum plot to choose the currently selected slice.
@@ -89,6 +89,7 @@ For your convenience, there are also player-style buttons with
 the following functionality:
 
 * Jump to first
+* Previous slice
 * Play/Pause
 * Next slice
 * Jump to last

jdaviz/components/toolbar_nested.py

@@ -53,17 +53,17 @@ def __init__(self, viewer, tools_nested, default_tool_priority=[]):
                               primary=i == 0,
                               visible=True)
 
-        # handle logic for tool visibilities (which will also handle setting the primary
-        # to something other than the first entry, if necessary)
-        self._update_tool_visibilities()
-
         # default_tool_priority allows falling back on an existing tool
         # if its the primary tool.  If no items in default_tool_priority
         # are currently "primary", then either no tool will be selected
         # or will fallback on BasicJupyterToolbar's handling of
         # viewer._default_mouse_mode_cls (which will not show that tool as active).
         self.default_tool_priority = default_tool_priority
-        self._handle_default_tool()
+
+        # handle logic for tool visibilities (which will also handle setting the primary
+        # to something other than the first entry, if necessary)
+        # NOTE: this will also call _handle_default_tool
+        self._update_tool_visibilities()
 
         # toolbars in the main app viewers need to respond to the data-collection, etc,
         # but those in plugins do not
@@ -132,6 +132,7 @@ def _update_tool_visibilities(self):
         self.send_state("tools_data")
         if needs_deactivate_active:
             self.active_tool_id = None
+        self._handle_default_tool()
 
     def _handle_default_tool(self):
         # default to the first item in the default_tool_priority list that is currently

jdaviz/configs/cubeviz/helper.py

@@ -1,6 +1,7 @@
 import numpy as np
 from astropy.io import fits
 from astropy.io import registry as io_registry
+from astropy.utils.decorators import deprecated
 from glue.core import BaseData
 from specutils import Spectrum1D
 from specutils.io.registers import _astropy_has_priorities
@@ -14,6 +15,10 @@
 __all__ = ['Cubeviz']
 
 
+_spectral_axis_names = ["Wave", "Wavelength", "Freq", "Frequency",
+                        "Wavenumber", "Velocity", "Energy"]
+
+
 class Cubeviz(ImageConfigHelper, LineListMixin):
     """Cubeviz Helper class"""
     _default_configuration = 'cubeviz'
@@ -36,8 +41,7 @@ def _set_spectrum_x_axis(self, msg):
             return
         ref_data = viewer.state.reference_data
         if ref_data and ref_data.ndim == 3:
-            for att_name in ["Wave", "Wavelength", "Freq", "Frequency",
-                             "Wavenumber", "Velocity", "Energy"]:
+            for att_name in _spectral_axis_names:
                 if att_name in ref_data.component_ids():
                     if viewer.state.x_att != ref_data.id[att_name]:
                         viewer.state.x_att = ref_data.id[att_name]
@@ -76,6 +80,7 @@ def load_data(self, data, data_label=None, override_cube_limit=False, **kwargs):
 
         super().load_data(data, parser_reference="cubeviz-data-parser", **kwargs)
 
+    @deprecated(since="3.9", alternative="select_wavelength")
     def select_slice(self, slice):
         """
         Select a slice by index.
@@ -89,8 +94,7 @@ def select_slice(self, slice):
             raise TypeError("slice must be an integer")
         if slice < 0:
             raise ValueError("slice must be positive")
-        msg = SliceSelectSliceMessage(slice=slice, sender=self)
-        self.app.hub.broadcast(msg)
+        self.plugins['Slice'].slice = slice
 
     def select_wavelength(self, wavelength):
         """
@@ -100,7 +104,7 @@ def select_wavelength(self, wavelength):
         ----------
         wavelength : float
             Wavelength to select in units of the x-axis of the spectrum.  The nearest slice will
-            be selected.
+            be selected if "snap to slice" is enabled in the slice plugin.
         """
         if not isinstance(wavelength, (int, float)):
             raise TypeError("wavelength must be a float or int")