Histogram bin size and limits (#2309)

* Allow setting of bin size and histogram limits

Add option to set histogram bin size and API for viewer limits

* Change stretch_hist_bin_size to stretch_hist_nbins

* Address review comments and add tests

* Fix bug and update tests

* Add methods to user api

* Remove x/y limits from user api

jdaviz/configs/default/plugins/plot_options/plot_options.py

@@ -18,6 +18,7 @@
                                         PlotOptionsSyncState)
 from jdaviz.core.user_api import PluginUserApi
 from jdaviz.core.tools import ICON_DIR
+from jdaviz.core.custom_traitlets import IntHandleEmpty
 from jdaviz.utils import bqplot_clear_figure
 from jdaviz.core.marks import HistogramMark
 
@@ -96,6 +97,7 @@ class PlotOptions(PluginTemplateMixin):
       not exposed for Specviz. This only applies when ``contour_mode`` is "Linear".
     * ``contour_custom_levels`` (:class:`~jdaviz.core.template_mixin.PlotOptionsSyncState`):
       not exposed for Specviz. This only applies when ``contour_mode`` is "Custom".
+    * :meth: `set_histogram_nbins`
     """
     template_file = __file__, "plot_options.vue"
 
@@ -189,6 +191,7 @@ class PlotOptions(PluginTemplateMixin):
     stretch_vmax_sync = Dict().tag(sync=True)
 
     stretch_hist_zoom_limits = Bool().tag(sync=True)
+    stretch_hist_nbins = IntHandleEmpty().tag(sync=True)
     stretch_histogram = Any().tag(sync=True, **widget_serialization)
 
     subset_visible_value = Bool().tag(sync=True)
@@ -428,7 +431,8 @@ def state_attr_for_line_visible(state):
 
     @property
     def user_api(self):
-        expose = ['multiselect', 'viewer', 'layer', 'select_all', 'subset_visible']
+        expose = ['multiselect', 'viewer', 'layer', 'select_all', 'subset_visible',
+                  'set_histogram_nbins']
         if self.config == "cubeviz":
             expose += ['collapse_function']
         if self.config != "imviz":
@@ -599,6 +603,7 @@ def _update_stretch_histogram(self, msg={}):
                                                        label='density')]
 
             self.bqplot_figs_resize = [self.stretch_histogram]
+            self.stretch_hist_nbins = 25
 
         else:
             hist_mark = self.stretch_histogram.marks[0]
@@ -623,11 +628,18 @@ def _add_histogram_marks(self):
             return
         scales = {'x': self.stretch_histogram.axes[0].scale, 'y': bqplot.LinearScale()}
         v_stretch_lines = []
-        if self.stretch_vmin.value >= self.stretch_histogram.marks[0].min:
+        # Set the viewer limits if they are None
+        if self.stretch_histogram.axes[0].scale.min is None:
+            self.stretch_histogram.axes[0].scale.min = self.stretch_histogram.marks[0].min
+        if self.stretch_histogram.axes[0].scale.max is None:
+            self.stretch_histogram.axes[0].scale.max = self.stretch_histogram.marks[0].max
+
+        # If the stretch limits are within the viewer limits, draw the HistogramMark
+        if self.stretch_vmin.value >= self.stretch_histogram.axes[0].scale.min:
             vmin_lines = HistogramMark(min_max_value=[self.stretch_vmin.value, self.stretch_vmin.value], # noqa
                                        scales=scales)
             v_stretch_lines.append(vmin_lines)
-        if self.stretch_vmax.value <= self.stretch_histogram.marks[0].max:
+        if self.stretch_vmax.value <= self.stretch_histogram.axes[0].scale.max:
             vmax_lines = HistogramMark(min_max_value=[self.stretch_vmax.value, self.stretch_vmax.value], # noqa
                                        scales=scales)
             v_stretch_lines.append(vmax_lines)
@@ -638,3 +650,25 @@ def _remove_histogram_marks(self):
             return
         self.stretch_histogram.marks = [mark for mark in self.stretch_histogram.marks
                                         if not isinstance(mark, HistogramMark)]
+
+    @observe("stretch_hist_nbins")
+    def histogram_nbins_changed(self, msg):
+        if self.stretch_histogram is None or msg['new'] == '' or msg['new'] < 1:
+            return
+        self.set_histogram_nbins(msg['new'])
+
+    def set_histogram_nbins(self, nbins):
+        self.stretch_histogram.marks[0].bins = nbins
+        self.stretch_hist_nbins = nbins
+
+    def set_histogram_x_limits(self, x_min, x_max):
+        if x_min:
+            self.stretch_histogram.axes[0].scale.min = x_min
+        if x_max:
+            self.stretch_histogram.axes[0].scale.max = x_max
+
+    def set_histogram_y_limits(self, y_min, y_max):
+        if y_min:
+            self.stretch_histogram.axes[1].scale.min = y_min
+        if y_max:
+            self.stretch_histogram.axes[1].scale.max = y_max

jdaviz/configs/default/plugins/plot_options/plot_options.vue

@@ -348,6 +348,16 @@
 
     <v-row v-if="stretch_function_sync.in_subscribed_states">
       <!-- z-index to ensure on top of the jupyter widget with negative margin-top -->
+      <v-text-field
+          ref="stretch_hist_nbins"
+          type="number"
+          label="Number of Bins"
+          v-model.number="stretch_hist_nbins"
+          hint="The amount of bins used in the histogram."
+          persistent-hint
+          :rules="[() => stretch_hist_nbins !== '' || 'This field is required',
+                   () => stretch_hist_nbins > 0 || 'Number of Bins must be greater than zero']"
+      ></v-text-field>
       <v-switch
         v-model="stretch_hist_zoom_limits"
         class="hide-input"

jdaviz/configs/default/plugins/plot_options/tests/test_plot_options.py

@@ -88,15 +88,27 @@ def test_stretch_histogram(cubeviz_helper, spectrum1d_cube_with_uncerts):
     po.stretch_hist_zoom_limits = True
     assert len(po.stretch_histogram.marks[0].sample) != len(flux_cube_sample)
 
-    po.stretch_vmin.value = po.stretch_histogram.marks[0].min
-    po.stretch_vmax.value = po.stretch_histogram.marks[0].max
+    po.stretch_vmin.value = 0.5
+    po.stretch_vmax.value = 1
 
     v_min_max_marks = [mark for mark in po.stretch_histogram.marks
                        if isinstance(mark, HistogramMark)]
     assert len(v_min_max_marks) == 2
     assert v_min_max_marks[0].x[0] == po.stretch_vmin.value
     assert v_min_max_marks[1].x[0] == po.stretch_vmax.value
 
+    assert po.stretch_histogram.marks[0].bins == 25
+    po.set_histogram_nbins(20)
+    assert po.stretch_histogram.marks[0].bins == 20
+
+    po.set_histogram_x_limits(x_min=0.25, x_max=2)
+    assert po.stretch_histogram.axes[0].scale.min == 0.25
+    assert po.stretch_histogram.axes[0].scale.max == 2
+
+    po.set_histogram_y_limits(y_min=1, y_max=2)
+    assert po.stretch_histogram.axes[1].scale.min == 1
+    assert po.stretch_histogram.axes[1].scale.max == 2
+
     po._remove_histogram_marks()
     assert len([mark for mark in po.stretch_histogram.marks
                 if isinstance(mark, HistogramMark)]) == 0