Embrace flexible box model

IPython/html/static/widgets/js/widget_container.js

@@ -19,7 +19,7 b' define(['
 
         render: function(){
             // Called when view is rendered.
-            this.$el.addClass('widget-container').addClass('vbox');
+            this.$el.addClass('widget-container');
         },
         
         update_children: function(old_list, new_list) {
@@ -45,6 +45,56 b' define(['
             });
         },
     });
+
+
+    var FlexContainerView = ContainerView.extend({
+        render: function(){
+            FlexContainerView.__super__.render.apply(this);
+            this.model.on('change:flex', this._flex_changed, this);
+            this.model.on('change:pack', this._pack_changed, this);
+            this.model.on('change:align', this._align_changed, this);
+            this._flex_changed();
+            this._pack_changed();
+            this._align_changed();
+        },
+
+        _flex_changed: function(){
+            if (this.model.previous('flex')) {
+                this.$el.removeClass('box-flex' + this.model.previous('flex'));
+            }
+            this.$el.addClass('box-flex' + this.model.get('flex'));
+        },
+
+        _pack_changed: function(){
+            if (this.model.previous('pack')) {
+                this.$el.removeClass(this.model.previous('pack'));
+            }
+            this.$el.addClass(this.model.get('pack'));
+        },
+
+        _align_changed: function(){
+            if (this.model.previous('align')) {
+                this.$el.removeClass('align-' + this.model.previous('align'));
+            }
+            this.$el.addClass('align-' + this.model.get('align'));
+        },
+    });
+
+
+    var VBoxContainerView = FlexContainerView.extend({
+        render: function(){
+            this.$el.addClass('vbox');
+            FlexContainerView.__super__.render.apply(this);
+        },
+    });
+
+
+    var HBoxContainerView = FlexContainerView.extend({
+        render: function(){
+            this.$el.addClass('hbox');
+            FlexContainerView.__super__.render.apply(this);
+        },
+    });
     
 
     var PopupView = widget.DOMWidgetView.extend({
@@ -279,5 +329,8 b' define(['
     return {
         'ContainerView': ContainerView,
         'PopupView': PopupView,
+        'FlexContainerView': FlexContainerView,
+        'VBoxContainerView': VBoxContainerView,
+        'HBoxContainerView': HBoxContainerView,
     };
 });

IPython/html/widgets/__init__.py

@@ -2,7 +2,7 b' from .widget import Widget, DOMWidget, CallbackDispatcher'
 
 from .widget_bool import CheckboxWidget, ToggleButtonWidget
 from .widget_button import ButtonWidget
-from .widget_container import ContainerWidget, PopupWidget
+from .widget_container import ContainerWidget, PopupWidget, FlexContainerWidget, HBoxContainerWidget, VBoxContainerWidget
 from .widget_float import FloatTextWidget, BoundedFloatTextWidget, FloatSliderWidget, FloatProgressWidget
 from .widget_image import ImageWidget
 from .widget_int import IntTextWidget, BoundedIntTextWidget, IntSliderWidget, IntProgressWidget

IPython/html/widgets/widget_container.py

@@ -7,7 +7,7 b' Represents a container that can be used to group other widgets.'
 # Distributed under the terms of the Modified BSD License.
 
 from .widget import DOMWidget
-from IPython.utils.traitlets import Unicode, Tuple, TraitError
+from IPython.utils.traitlets import Unicode, Tuple, TraitError, Int, CaselessStrEnum
 
 class ContainerWidget(DOMWidget):
     _view_name = Unicode('ContainerView', sync=True)
@@ -32,3 +32,24 b' class PopupWidget(ContainerWidget):'
     
     description = Unicode(sync=True)
     button_text = Unicode(sync=True)
+
+
+class FlexContainerWidget(ContainerWidget):
+    _view_name = Unicode('FlexContainerView', sync=True)
+    flex = Int(0, sync=True, help="""Specify the flexible-ness of the model.""")
+    def _flex_changed(self, name, old, new):
+        new = min(max(0, new), 2)
+        if self.flex != new:
+            self.flex = new
+
+    _locations = ['start', 'center', 'end']
+    pack = CaselessStrEnum(values=_locations, default_value='start', allow_none=False, sync=True)
+    align = CaselessStrEnum(values=_locations, default_value='start', allow_none=False, sync=True)
+
+
+class VBoxContainerWidget(FlexContainerWidget):
+    _view_name = Unicode('VBoxContainerView', sync=True)
+
+
+class HBoxContainerWidget(FlexContainerWidget):
+    _view_name = Unicode('HBoxContainerView', sync=True)