Use JS events for switching kernelspecs

IPython/html/static/notebook/js/kernelselector.js

@@ -11,12 +11,13 b' define(['
     var KernelSelector = function(selector, notebook) {
         this.selector = selector;
         this.notebook = notebook;
+        this.events = notebook.events;
         this.kernelspecs = {};
         if (this.selector !== undefined) {
             this.element = $(selector);
             this.request_kernelspecs();
         }
-
+        this.bind_events();
         // For now, this is how we make this object available elsewhere
         IPython.kernelselector = this;
     };
@@ -44,15 +45,17 b' define(['
         if (kernel_name === this.notebook.kernel.name) {
             return;
         }
+        var ks = this.kernelspecs[kernel_name];
+        this.events.trigger('spec_changed.Kernel', ks);
         this.notebook.session.delete();
         this.notebook.start_session(kernel_name);
     };
     
-    KernelSelector.prototype.set_displayed_name = function(kernel_name) {
-        var ks = this.kernelspecs[kernel_name]
-        if (ks !== undefined) {
-            this.element.find("#current_kernel_spec").text(ks.display_name);
-        }
+    KernelSelector.prototype.bind_events = function() {
+        var that = this;
+        this.events.on('spec_changed.Kernel', function(event, data) {
+            that.element.find("#current_kernel_spec").text(data.display_name);
+        });
     };
 
     return {'KernelSelector': KernelSelector};

IPython/html/static/notebook/js/notebook.js

@@ -215,6 +215,13 b' define(['
                 }
             });
         });
+        
+        this.events.on('spec_changed.Kernel', function(event, data) {
+            that.set_kernelspec_metadata(data);
+            if (data.codemirror_mode) {
+                that.set_codemirror_mode(data.codemirror_mode);
+            }
+        });
 
         var collapse_time = function (time) {
             var app_height = $('#ipython-main-app').height(); // content height
@@ -338,8 +345,7 b' define(['
             keyboard_manager: this.keyboard_manager});
     };
     
-    Notebook.prototype.set_kernelspec_metadata = function(kernel_name) {
-        var ks = IPython.kernelselector.kernelspecs[kernel_name]
+    Notebook.prototype.set_kernelspec_metadata = function(ks) {
         var tostore = {};
         for (field in ks) {
             if (field !== 'argv' && field !== 'env') {
@@ -347,11 +353,6 b' define(['
             }
         }
         this.metadata.kernelspec = tostore;
-        
-        // Update the codemirror mode for code cells
-        if (tostore.codemirror_mode) {
-            this.set_codemirror_mode(tostore.codemirror_mode);
-        }
     }
 
     // Cell indexing, retrieval, etc.
@@ -1781,10 +1782,10 b' define(['
         this.notebook_name = data.name;
         var trusted = true;
         
-        // Set the default codemirror mode before we load the cells
-        var cm_mode = (this.metadata.kernelspec || {}).codemirror_mode;
-        if (cm_mode) {
-            this.set_codemirror_mode(cm_mode);
+        // Trigger an event changing the kernel spec - this will set the default
+        // codemirror mode
+        if (this.metadata.kernelspec !== undefined) {
+            this.events.trigger('spec_changed.Kernel', this.metadata.kernelspec);
         }
         
         // Only handle 1 worksheet for now.

IPython/html/static/services/sessions/js/session.js

@@ -91,13 +91,17 b' define(['
      */
     Session.prototype._handle_start_success = function (data, status, xhr) {
         this.id = data.id;
-        // If we asked for 'python', the response will have 'python3' or 'python2'
-        this.kernel_name = data.kernel.name;
+        // If we asked for 'python', the response will have 'python3' or 'python2'.
+        // In this case, fire the spec changed event again to update the name
+        // and highlighting.
+        if (data.kernel.name !== this.kernel_name) {
+            this.kernel_name = data.kernel.name;
+            var ks = IPython.kernelselector.kernelspecs[this.kernel_name];
+            this.notebook.events.trigger('spec_changed.Kernel', ks);
+        }
         var kernel_service_url = utils.url_path_join(this.base_url, "api/kernels");
         this.kernel = new kernel.Kernel(kernel_service_url, this.ws_url, this.notebook, this.kernel_name);
         this.kernel._kernel_started(data.kernel);
-        IPython.kernelselector.set_displayed_name(this.kernel_name);
-        this.notebook.set_kernelspec_metadata(this.kernel_name);
     };
     
     /**