Mirror events on an internal event handler

src/lib/events.js

@@ -24,6 +24,7 @@ var Events = {
         if(plotObj._ev instanceof EventEmitter) return plotObj;
 
         var ev = new EventEmitter();
+        var internalEv = new EventEmitter();
 
         /*
          * Assign to plot._ev while we still live in a land
@@ -32,6 +33,16 @@ var Events = {
          */
         plotObj._ev = ev;
 
+        /*
+         * Create a second event handler that will manage events *internally*.
+         * This allows parts of plotly to respond to thing like relayout without
+         * having to use the user-facing event handler. They cannot peacefully
+         * coexist on the same handler because a user invoking
+         * plotObj.removeAllListeners() would detach internal events, breaking
+         * plotly.
+         */
+        plotObj._internalEv = internalEv;
+
         /*
          * Assign bound methods from the ev to the plot object. These methods
          * will reference the 'this' of plot._ev even though they are methods
@@ -46,6 +57,15 @@ var Events = {
         plotObj.removeListener = ev.removeListener.bind(ev);
         plotObj.removeAllListeners = ev.removeAllListeners.bind(ev);
 
+        /*
+         * Create funtions for managing internal events. These are *only* triggered
+         * by the mirroring of external events via the emit function.
+         */
+        plotObj._internalOn = internalEv.on.bind(internalEv);
+        plotObj._internalOnce = internalEv.once.bind(internalEv);
+        plotObj._removeInternalListener = internalEv.removeListener.bind(internalEv);
+        plotObj._removeAllInternalListeners = internalEv.removeAllListeners.bind(internalEv);
+
         /*
          * We must wrap emit to continue to support JQuery events. The idea
          * is to check to see if the user is using JQuery events, if they are
@@ -58,6 +78,7 @@ var Events = {
             }
 
             ev.emit(event, data);
+            internalEv.emit(event, data);
         };
 
         return plotObj;
@@ -68,6 +89,10 @@ var Events = {
      * all handlers for a particular event and returns the return value
      * of the LAST handler. This function also triggers jQuery's
      * triggerHandler for backwards compatibility.
+     *
+     * Note: triggerHandler has been recommended for deprecation in v2.0.0,
+     * so the additional behavior of triggerHandler triggering internal events
+     * is deliberate excluded in order to avoid reinforcing more usage.
      */
     triggerHandler: function(plotObj, event, data) {
         var jQueryHandlerValue;
@@ -124,6 +149,13 @@ var Events = {
         delete plotObj.removeAllListeners;
         delete plotObj.emit;
 
+        delete plotObj._ev;
+        delete plotObj._internalEv;
+        delete plotObj._internalOn;
+        delete plotObj._internalOnce;
+        delete plotObj._removeInternalListener;
+        delete plotObj._removeAllInternalListeners;
+
         return plotObj;
     }
 

test/jasmine/tests/events_test.js

@@ -70,6 +70,19 @@ describe('Events', function() {
                 $(plotDiv).trigger('ping', 'pong');
             });
         });
+
+        it('mirrors events on an internal handler', function(done) {
+            Events.init(plotDiv);
+
+            plotDiv._internalOn('ping', function(data) {
+                expect(data).toBe('pong');
+                done();
+            });
+
+            setTimeout(function() {
+                plotDiv.emit('ping', 'pong');
+            });
+        });
     });
 
     describe('triggerHandler', function() {
@@ -100,6 +113,34 @@ describe('Events', function() {
             expect(result).toBe('pong');
         });
 
+        it('does *not* mirror triggerHandler events on the internal handler', function() {
+            var eventBaton = 0;
+            var internalEventBaton = 0;
+
+            Events.init(plotDiv);
+
+            plotDiv.on('ping', function() {
+                eventBaton++;
+                return 'ping';
+            });
+
+            plotDiv._internalOn('ping', function() {
+                internalEventBaton++;
+                return 'foo';
+            });
+
+            plotDiv.on('ping', function() {
+                eventBaton++;
+                return 'pong';
+            });
+
+            var result = Events.triggerHandler(plotDiv, 'ping');
+
+            expect(eventBaton).toBe(2);
+            expect(internalEventBaton).toBe(0);
+            expect(result).toBe('pong');
+        });
+
         it('triggers jQuery handlers when no matching node events bound', function() {
             var eventBaton = 0;
 

test/jasmine/tests/plots_test.js

@@ -301,9 +301,10 @@ describe('Test Plots', function() {
 
         it('should unset everything in the gd except _context', function() {
             var expectedKeys = [
-                '_ev', 'on', 'once', 'removeListener', 'removeAllListeners',
-                'emit', '_context', '_replotPending', '_mouseDownTime',
-                '_hmpixcount', '_hmlumcount'
+                '_ev', '_internalEv', 'on', 'once', 'removeListener', 'removeAllListeners',
+                '_internalOn', '_internalOnce', '_removeInternalListener',
+                '_removeAllInternalListeners', 'emit', '_context', '_replotPending',
+                '_mouseDownTime', '_hmpixcount', '_hmlumcount'
             ];
 
             Plots.purge(gd);