replace ping plugin with method

* to avoid unnecessary traitlet syncing

docs/dev/ui_style_guide.rst

@@ -8,7 +8,7 @@ Tray Plugins
 In order to be consistent with layout, styling, and spacing, UI development on plugins should
 try to adhere to the following principles:
 
-* Any tray plugin should utilize ``<j-tray-plugin :uses_active_status="uses_active_status" :plugin_ping.sync="plugin_ping" :keep_active.sync="keep_active" :disabled_msg='disabled_msg' :popout_button="popout_button">`` as the
+* Any tray plugin should utilize ``<j-tray-plugin :uses_active_status="uses_active_status" @plugin-ping="plugin_ping($event)" :keep_active.sync="keep_active" :disabled_msg='disabled_msg' :popout_button="popout_button">`` as the
   outer-container (which provides consistent styling rules).  Any changes to style
   across all plugins should then take place in the
   ``j-tray-plugin`` stylesheet (``jdaviz/components/tray_plugin.vue``).

jdaviz/components/tray_plugin.vue

@@ -30,7 +30,7 @@
 <script>
 module.exports = {
   props: ['disabled_msg', 'description', 'link', 'popout_button',
-          'uses_active_status', 'plugin_ping', 'keep_active'],
+          'uses_active_status', 'keep_active'],
   methods: {
     isDisabled() {
       return this.getDisabledMsg().length > 0
@@ -43,7 +43,7 @@ module.exports = {
         return
       }
       if (!document.hidden) {
-        this.$emit('update:plugin_ping', Date.now())
+        this.$emit('plugin-ping', Date.now())
       }
       if (!recursive) {
         return

jdaviz/configs/default/plugins/markers/markers.vue

@@ -3,7 +3,7 @@
     description='Create and export markers.  Press "m" with the cursor over a viewer to log the mouseover information.  To change the selected layer, click the layer cycler in the mouseover information section of the app-level toolbar.'
     :link="'https://jdaviz.readthedocs.io/en/'+vdocs+'/'+config+'/plugins.html#markers'"
     :uses_active_status="uses_active_status"
-    :plugin_ping.sync="plugin_ping"
+    @plugin-ping="plugin_ping($event)"
     :keep_active.sync="keep_active"
     :popout_button="popout_button">
 

jdaviz/configs/specviz/plugins/line_analysis/line_analysis.vue

@@ -3,7 +3,7 @@
     description="Return statistics for a single spectral line."
     :link="'https://jdaviz.readthedocs.io/en/'+vdocs+'/'+config+'/plugins.html#line-analysis'"
     :uses_active_status="uses_active_status"
-    :plugin_ping.sync="plugin_ping"
+    @plugin-ping="plugin_ping($event)"
     :keep_active.sync="keep_active"
     :disabled_msg="disabled_msg"
     :popout_button="popout_button">

jdaviz/configs/specviz2d/plugins/spectral_extraction/spectral_extraction.vue

@@ -3,7 +3,7 @@
     description="2D to 1D spectral extraction."
     :link="'https://jdaviz.readthedocs.io/en/'+vdocs+'/'+config+'/plugins.html#spectral-extraction'"
     :uses_active_status="uses_active_status"
-    :plugin_ping.sync="plugin_ping"
+    @plugin-ping="plugin_ping($event)"
     :keep_active.sync="keep_active"
     :popout_button="popout_button">
 

jdaviz/core/template_mixin.py

@@ -22,7 +22,7 @@
 from glue_jupyter.bqplot.image import BqplotImageView
 from glue_jupyter.widgets.linked_dropdown import get_choices as _get_glue_choices
 from specutils import Spectrum1D
-from traitlets import Any, Bool, HasTraits, Integer, List, Unicode, observe
+from traitlets import Any, Bool, HasTraits, List, Unicode, observe
 
 from ipywidgets import widget_serialization
 from ipypopout import PopoutButton
@@ -228,7 +228,6 @@ class PluginTemplateMixin(TemplateMixin):
     This base class can be inherited by all sidebar/tray plugins to expose common functionality.
     """
     disabled_msg = Unicode("").tag(sync=True)
-    plugin_ping = Integer(0).tag(sync=True)
     plugin_opened = Bool(False).tag(sync=True)  # noqa any instance of the plugin is open (recently sent an "alive" ping)
     uses_active_status = Bool(False).tag(sync=True)  # noqa whether the plugin has live-preview marks, set to True in plugins to expose keep_active switch
     keep_active = Bool(False).tag(sync=True)  # noqa whether the live-preview marks show regardless of active state, inapplicable unless uses_active_status is True
@@ -237,6 +236,7 @@ class PluginTemplateMixin(TemplateMixin):
     def __init__(self, **kwargs):
         self._viewer_callbacks = {}
         self._inactive_thread = None  # thread checking for alive pings to control plugin_opened
+        self._ping_timestamp = 0
         super().__init__(**kwargs)
 
     @property
@@ -245,11 +245,9 @@ def user_api(self):
         # can even be dependent on config, etc.
         return PluginUserApi(self, expose=[])
 
-    @observe('plugin_ping')
-    def _plugin_ping_changed(self, *args):
-        if self.plugin_ping == 0:
-            # initial traitlet state
-            return
+    def vue_plugin_ping(self, ping_timestamp):
+        self._ping_timestamp = ping_timestamp
+
         # we've received a ping, so immediately set plugin_opened state to True
         if not self.plugin_opened:
             self.plugin_opened = True
@@ -271,7 +269,7 @@ def _watch_active(self):
         expected_delay_ms = 200
         # plugin_ping (ms) set by setTimeout in tray_plugin.vue
         # time.time() is in s, so need to convert to ms
-        while time.time()*1000 - self.plugin_ping < 2 * expected_delay_ms:
+        while time.time()*1000 - self._ping_timestamp < 2 * expected_delay_ms:
             # at least one plugin has sent an "alive" ping within twice of the expected
             # interval, wait a full (double) interval and then check again
             time.sleep(2 * expected_delay_ms / 1000)