Added baseline and stretch

IPython/html/static/base/less/flexbox.less

@@ -184,6 +184,30 b' Browsers not listed, including Safari, are supported via the styling under the'
     justify-content: center;
 }
 
+.hbox.baseline, 
+.vbox.baseline,
+.baseline {
+    /* Old browsers */
+    -webkit-box-pack: baseline;
+    -moz-box-pack: baseline;
+    box-pack: baseline;
+    
+    /* Modern browsers */
+    justify-content: baseline;
+}
+
+.hbox.stretch, 
+.vbox.stretch,
+.stretch {
+    /* Old browsers */
+    -webkit-box-pack: stretch;
+    -moz-box-pack: stretch;
+    box-pack: stretch;
+    
+    /* Modern browsers */
+    justify-content: stretch;
+}
+
 .hbox.align-start, 
 .vbox.align-start,
 .align-start {
@@ -219,3 +243,27 b' Browsers not listed, including Safari, are supported via the styling under the'
     /* Modern browsers */
     align-items: center;
 }
+
+.hbox.align-baseline, 
+.vbox.align-baseline,
+.align-baseline {
+    /* Old browsers */
+    -webkit-box-align: baseline;
+    -moz-box-align: baseline;
+    box-align: baseline;
+    
+    /* Modern browsers */
+    align-items: baseline;
+}
+
+.hbox.align-stretch, 
+.vbox.align-stretch,
+.align-stretch {
+    /* Old browsers */
+    -webkit-box-align: stretch;
+    -moz-box-align: stretch;
+    box-align: stretch;
+    
+    /* Modern browsers */
+    align-items: stretch;
+}

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, FlexContainerWidget, HBoxContainerWidget, VBoxContainerWidget
+from .widget_container import ContainerWidget, PopupWidget, FlexContainerWidget, HBoxWidget, VBoxWidget
 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

@@ -42,14 +42,18 b' class FlexContainerWidget(ContainerWidget):'
         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)
+    _locations = ['start', 'center', 'end', 'baseline', 'stretch']
+    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):
+class VBoxWidget(FlexContainerWidget):
     _view_name = Unicode('VBoxContainerView', sync=True)
 
 
-class HBoxContainerWidget(FlexContainerWidget):
+class HBoxWidget(FlexContainerWidget):
     _view_name = Unicode('HBoxContainerView', sync=True)