redshift input: move float case into js

* avoids a float cast on every slider move

jdaviz/configs/default/plugins/line_lists/line_lists.py

@@ -194,8 +194,10 @@ def _on_slider_updated(self, event):
             return
 
         # NOTE: _on_rs_redshift_updated will handle updating rs_rv
-        # NOTE: rs_redshift could be a string if entered by the user, so we cast old value to float
-        self.rs_redshift = float(self.rs_redshift) + event['new'] - event['old']
+        # NOTE: the input has a custom @input method in line_lists.vue to cast
+        # to float so that we can assume its a float here to minimize lag
+        # when interacting with the slider.
+        self.rs_redshift = self.rs_redshift + event['new'] - event['old']
 
     @observe('rs_redshift')
     def _on_rs_redshift_updated(self, event):

jdaviz/configs/default/plugins/line_lists/line_lists.vue

@@ -35,7 +35,8 @@
     <v-row class="row-no-outside-padding row-min-bottom-padding">
       <v-col>
         <v-text-field
-          v-model="rs_redshift"
+          :value='rs_redshift'
+          @input='setRedshiftFloat'
           step="0.1"
           class="mt-0 pt-0"
           type="number"
@@ -254,6 +255,9 @@
       this.throttledSlider = _.throttle(
         (v) => { this.rs_slider = v; },
         this.rs_slider_throttle);
+      this.setRedshiftFloat = (v) => {
+        this.rs_redshift = parseFloat(v)
+      }
     },
   }
 </script>