fix(AbstractWidget): Ensure we do not re-register callbacks

`listenEvents` would usually be called by `setEnable` and `setInteractor`,
which would register callbacks twice. Also, `listenEvents` is part of the
publicAPI, so callbacks could have been registered again by explicitly
calling that function.

We now ensure that those callbacks are unsubscribed from the event before
subscribing again.

Sources/Interaction/Widgets/AbstractWidget/index.js

@@ -20,6 +20,13 @@ function vtkAbstractWidget(publicAPI, model) {
       vtkErrorMacro('The interactor must be set before listening events');
       return;
     }
+
+    // Remove current events
+    while (model.unsubscribes.length) {
+      model.unsubscribes.pop().unsubscribe();
+    }
+
+    // Check what events we can handle and register callbacks
     vtkRenderWindowInteractor.handledEvents.forEach((eventName) => {
       if (publicAPI[`handle${eventName}`]) {
         model.unsubscribes.push(
@@ -36,17 +43,9 @@ function vtkAbstractWidget(publicAPI, model) {
     if (i === model.interactor) {
       return;
     }
-
-    // if we already have an Interactor then stop observing it
-    if (model.interactor) {
-      while (model.unsubscribes.length) {
-        model.unsubscribes.pop().unsubscribe();
-      }
-    }
-
     model.interactor = i;
 
-    if (i) {
+    if (i && model.enabled) {
       publicAPI.listenEvents();
     }
 
@@ -60,11 +59,11 @@ function vtkAbstractWidget(publicAPI, model) {
   };
 
   publicAPI.setEnable = (enable) => {
+    if (enable === model.enabled) {
+      return;
+    }
+
     if (enable) {
-      if (model.enabled) {
-        // widget already enabled
-        return;
-      }
       if (!model.interactor) {
         vtkErrorMacro(
           'The interactor must be set prior to enabling the widget'
@@ -97,13 +96,9 @@ function vtkAbstractWidget(publicAPI, model) {
       model.widgetRep.buildRepresentation();
       model.currentRenderer.addViewProp(model.widgetRep);
     } else {
-      if (!model.enabled) {
-        // already
-        return;
-      }
       model.enabled = 0;
 
-      // Don't listen events
+      // Don't listen to events
       while (model.unsubscribes.length) {
         model.unsubscribes.pop().unsubscribe();
       }