Merge pull request #439 from atom/fb-mdt-delay-item-activation

Delay activation of item on mousedown event

lib/tab-bar-view.coffee

@@ -404,8 +404,14 @@ class TabBarView
       @rightClickedTab.element.classList.add('right-clicked')
       event.preventDefault()
     else if event.which is 1 and not event.target.classList.contains('close-icon')
-      @pane.activateItem(tab.item)
-      setImmediate => @pane.activate() unless @pane.isDestroyed()
+      # Delay action. This is important because the browser will set the focus
+      # as part of the default action of the mousedown event; therefore, any
+      # change we make to the focus as part of the handler would be overwritten.
+      # We could use `preventDefault()` to address this, but that would also
+      # make the tab undraggable.
+      setImmediate =>
+        @pane.activateItem(tab.item)
+        @pane.activate() unless @pane.isDestroyed()
     else if event.which is 2
       @pane.destroyItem(tab.item)
       event.preventDefault()

spec/tabs-spec.coffee

@@ -261,19 +261,25 @@ describe "TabBarView", ->
       spyOn(pane, 'activate')
 
       event = triggerMouseEvent('mousedown', tabBar.tabAtIndex(0).element, which: 1)
-      expect(pane.getActiveItem()).toBe pane.getItems()[0]
-      expect(event.preventDefault).not.toHaveBeenCalled() # allows dragging
-
-      event = triggerMouseEvent('mousedown', tabBar.tabAtIndex(2).element, which: 1)
-      expect(pane.getActiveItem()).toBe pane.getItems()[2]
-      expect(event.preventDefault).not.toHaveBeenCalled() # allows dragging
-
       # Pane activation is delayed because focus is stolen by the tab bar
       # immediately afterward unless propagation of the mousedown event is
       # stopped. But stopping propagation of the mousedown event prevents the
       # dragstart event from occurring.
-      waits(1)
-      runs -> expect(pane.activate.callCount).toBe 2
+      expect(pane.getActiveItem()).not.toBe(pane.getItems()[0])
+      waitsFor ->
+        pane.getActiveItem() is pane.getItems()[0]
+
+      runs ->
+        expect(event.preventDefault).not.toHaveBeenCalled() # allows dragging
+        event = triggerMouseEvent('mousedown', tabBar.tabAtIndex(2).element, which: 1)
+        expect(pane.getActiveItem()).not.toBe(pane.getItems()[2])
+
+      waitsFor ->
+        pane.getActiveItem() is pane.getItems()[2]
+
+      runs ->
+        expect(event.preventDefault).not.toHaveBeenCalled() # allows dragging
+        expect(pane.activate.callCount).toBe 2
 
     it "closes the tab when middle clicked", ->
       jasmine.attachToDOM(tabBar.element) # Remove after Atom 1.2.0 is released