🚑 Fix widget crash when moving from Aladin Lite view

examples/6_Linked-widgets.ipynb

@@ -27,12 +27,12 @@
     "c = Aladin(layout=Layout(width=\"33.33%\"), survey=\"P/2MASS/color\", **cosmetic_options)\n",
     "\n",
     "# synchronize target between 3 widgets\n",
-    "widgets.jslink((a, \"shared_target\"), (b, \"shared_target\"))\n",
-    "widgets.jslink((b, \"shared_target\"), (c, \"shared_target\"))\n",
+    "widgets.jslink((a, \"_target\"), (b, \"_target\"))\n",
+    "widgets.jslink((b, \"_target\"), (c, \"_target\"))\n",
     "\n",
     "# synchronize FoV (zoom level) between 3 widgets\n",
-    "widgets.jslink((a, \"shared_fov\"), (b, \"shared_fov\"))\n",
-    "widgets.jslink((b, \"shared_fov\"), (c, \"shared_fov\"))\n",
+    "widgets.jslink((a, \"_fov\"), (b, \"_fov\"))\n",
+    "widgets.jslink((b, \"_fov\"), (c, \"_fov\"))\n",
     "\n",
     "items = [a, b, c]\n",
     "\n",

js/models/event_handler.js

@@ -31,45 +31,55 @@ export default class EventHandler {
     // is also necessary for the field of view.
 
     /* Target control */
-    let targetLock = new Lock();
+    const jsTargetLock = new Lock();
+    const pyTargetLock = new Lock();
 
     // Event triggered when the user moves the map in Aladin Lite
-    this.aladin.on("positionChanged", () => {
-      if (targetLock.locked) {
-        targetLock.unlock();
+    this.aladin.on("positionChanged", (position) => {
+      if (pyTargetLock.locked) {
+        pyTargetLock.unlock();
         return;
       }
-      targetLock.lock();
-      const raDec = this.aladin.getRaDec();
+      jsTargetLock.lock();
+      const raDec = [position.ra, position.dec];
+      // const raDec = this.aladin.getRaDec();
       this.model.set("_target", `${raDec[0]} ${raDec[1]}`);
-      this.model.set("shared_target", `${raDec[0]} ${raDec[1]}`);
       this.model.save_changes();
     });
 
-    // Event triggered when the target is changed from the Python side using jslink
-    this.model.on("change:shared_target", () => {
-      const target = this.model.get("shared_target");
+    this.model.on("change:_target", () => {
+      if (jsTargetLock.locked) {
+        jsTargetLock.unlock();
+        return;
+      }
+      pyTargetLock.lock();
+      let target = this.model.get("_target");
       const [ra, dec] = target.split(" ");
       this.aladin.gotoRaDec(ra, dec);
     });
 
     /* Field of View control */
-    let fovLock = new Lock();
+    const jsFovLock = new Lock();
+    const pyFovLock = new Lock();
 
     this.aladin.on("zoomChanged", (fov) => {
-      if (fovLock.locked) {
-        fovLock.unlock();
+      if (pyFovLock.locked) {
+        pyFovLock.unlock();
         return;
       }
-      fovLock.lock();
+      jsFovLock.lock();
       // fov MUST be cast into float in order to be sent to the model
       this.model.set("_fov", parseFloat(fov.toFixed(5)));
-      this.model.set("shared_fov", parseFloat(fov.toFixed(5)));
       this.model.save_changes();
     });
 
-    this.model.on("change:shared_fov", () => {
-      let fov = this.model.get("shared_fov");
+    this.model.on("change:_fov", () => {
+      if (jsFovLock.locked) {
+        jsFovLock.unlock();
+        return;
+      }
+      pyFovLock.lock();
+      let fov = this.model.get("_fov");
       this.aladin.setFoV(fov);
     });
 
@@ -186,8 +196,8 @@ export default class EventHandler {
    * There is no need to unsubscribe from the Aladin Lite events.
    */
   unsubscribeAll() {
-    this.model.off("change:shared_target");
-    this.model.off("change:fov");
+    this.model.off("change:_target");
+    this.model.off("change:_fov");
     this.model.off("change:height");
     this.model.off("change:coo_frame");
     this.model.off("change:survey");

js/utils.js

@@ -28,18 +28,16 @@ class Lock {
 
   /**
    * Locks the object
-   * @returns {boolean} True if the object was locked, false otherwise
    */
   unlock() {
-    return false;
+    this.locked = false;
   }
 
   /**
    * Unlocks the object
-   * @returns {boolean} True if the object was unlocked, false otherwise
    */
   lock() {
-    return true;
+    this.locked = true;
   }
 }
 

src/ipyaladin/aladin.py

@@ -45,22 +45,12 @@ class Aladin(anywidget.AnyWidget):
         " Its public version is the 'target' property that returns an "
         "`~astropy.coordinates.SkyCoord` object",
     ).tag(sync=True, init_option=True)
-    shared_target = Unicode(
-        "0 0",
-        help="A trait that can be used with `~ipywidgets.widgets.jslink`"
-        "to link two Aladin Lite widgets targets together",
-    ).tag(sync=True)
     _fov = Float(
         60.0,
         help="A private trait that stores the current field of view of the widget."
         " Its public version is the 'fov' property that returns an "
         "`~astropy.units.Angle` object",
     ).tag(sync=True, init_option=True)
-    shared_fov = Float(
-        60.0,
-        help="A trait that can be used with `~ipywidgets.widgets.jslink`"
-        "to link two Aladin Lite widgets field of view together",
-    ).tag(sync=True)
     survey = Unicode("https://alaskybis.unistra.fr/DSS/DSSColor").tag(
         sync=True, init_option=True
     )