Abstract out the notion of a traitlet instance type that can be initialized with a dict

ipywidgets/widgets/domwidget.py

@@ -5,20 +5,16 @@
 
 from traitlets import Unicode, Bool, Tuple, default
 from .widget import Widget, widget_serialization
-from .trait_types import Color
-from .widget_layout import Layout, LayoutTraitType
+from .trait_types import Color, InstanceDict
+from .widget_layout import Layout
 
 
 class DOMWidget(Widget):
     """Widget that can be inserted into the DOM"""
 
     _model_name = Unicode('DOMWidgetModel').tag(sync=True)
     _dom_classes = Tuple(help="CSS classes applied to widget DOM element").tag(sync=True)
-    layout = LayoutTraitType().tag(sync=True, **widget_serialization)
-
-    @default('layout')
-    def _default_layout(self):
-        return Layout()
+    layout = InstanceDict(Layout).tag(sync=True, **widget_serialization)
 
     def add_class(self, className):
         """

ipywidgets/widgets/trait_types.py

@@ -78,3 +78,20 @@ def datetime_from_json(js, manager):
     'from_json': datetime_from_json,
     'to_json': datetime_to_json
 }
+
+class InstanceDict(traitlets.Instance):
+    """An instance trait which coerces a dict to an instance.
+    
+    This lets the instance be specified as a dict, which is used to initialize the instance.
+    
+    Also, we default to a trivial instance, even if args and kwargs is not specified."""
+
+    def validate(self, obj, value):
+        if isinstance(value, dict):
+            return super(InstanceDict, self).validate(obj, self.klass(**value))
+        else:
+            return super(InstanceDict, self).validate(obj, value)
+
+    def make_dynamic_default(self):
+        return self.klass(*(self.default_args or ()),
+                          **(self.default_kwargs or {}))

ipywidgets/widgets/widget_button.py

@@ -11,7 +11,7 @@
 from .widget import CallbackDispatcher, register, widget_serialization
 from .widget_core import CoreWidget
 from .widget_style import Style
-from .trait_types import Color
+from .trait_types import Color, InstanceDict
 
 from traitlets import Unicode, Bool, CaselessStrEnum, Instance, validate, default
 import warnings
@@ -55,11 +55,7 @@ class Button(DOMWidget, CoreWidget):
         values=['primary', 'success', 'info', 'warning', 'danger', ''], default_value='',
         help="""Use a predefined styling for the button.""").tag(sync=True)
 
-    style = Instance(ButtonStyle).tag(sync=True, **widget_serialization)
-
-    @default('style')
-    def _default_style(self):
-        return ButtonStyle()
+    style = InstanceDict(ButtonStyle).tag(sync=True, **widget_serialization)
 
     def __init__(self, **kwargs):
         super(Button, self).__init__(**kwargs)

ipywidgets/widgets/widget_float.py

@@ -6,15 +6,15 @@
 # Copyright (c) Jupyter Development Team.
 # Distributed under the terms of the Modified BSD License.
 
+from traitlets import (
+    Instance, Unicode, CFloat, Bool, CaselessStrEnum, Tuple, TraitError, validate, default
+)
 from .domwidget import LabeledWidget
+from .trait_types import InstanceDict
 from .valuewidget import ValueWidget
 from .widget import register, widget_serialization
 from .widget_core import CoreWidget
-from .trait_types import Color
-from .widget_int import ProgressStyle
-from traitlets import (
-    Instance, Unicode, CFloat, Bool, Int, CaselessStrEnum, Tuple, TraitError, validate, default
-)
+from .widget_int import ProgressStyle, SliderStyle
 
 
 class _Float(LabeledWidget, ValueWidget, CoreWidget):
@@ -75,8 +75,6 @@ class FloatText(_Float):
         value displayed
     description : str
         description displayed next to the text box
-    color : str Unicode color code (eg. '#C13535')
-        color of the value displayed
     """
     _view_name = Unicode('FloatTextView').tag(sync=True)
     _model_name = Unicode('FloatTextModel').tag(sync=True)
@@ -98,8 +96,6 @@ class BoundedFloatText(_BoundedFloat):
         maximal value of the range of possible values displayed
     description : str
         description displayed next to the textbox
-    color : str Unicode color code (eg. '#C13535')
-        color of the value displayed
     """
     _view_name = Unicode('FloatTextView').tag(sync=True)
     _model_name = Unicode('FloatTextModel').tag(sync=True)
@@ -129,10 +125,6 @@ class FloatSlider(_BoundedFloat):
         default is '.2f', specifier for the format function used to represent
         slider value for human consumption, modeled after Python 3's format
         specification mini-language (PEP 3101).
-    slider_color : str Unicode color code (eg. '#C13535')
-        color of the slider
-    color : str Unicode color code (eg. '#C13535')
-        color of the value displayed (if readout == True)
     """
     _view_name = Unicode('FloatSliderView').tag(sync=True)
     _model_name = Unicode('FloatSliderModel').tag(sync=True)
@@ -141,9 +133,10 @@ class FloatSlider(_BoundedFloat):
     _range = Bool(False, help="Display a range selector").tag(sync=True)
     readout = Bool(True, help="Display the current value of the slider next to it.").tag(sync=True)
     readout_format = Unicode('.2f', help="Format for the readout").tag(sync=True)
-    slider_color = Color(None, allow_none=True).tag(sync=True)
     continuous_update = Bool(True, help="Update the value of the widget as the user is holding the slider.").tag(sync=True)
 
+    style = InstanceDict(SliderStyle).tag(sync=True, **widget_serialization)
+
 
 @register
 class FloatProgress(_BoundedFloat):
@@ -177,11 +170,7 @@ class FloatProgress(_BoundedFloat):
         default_value='', allow_none=True,
         help="Use a predefined styling for the progess bar.").tag(sync=True)
 
-    style = Instance(ProgressStyle).tag(sync=True, **widget_serialization)
-
-    @default('style')
-    def _default_style(self):
-        return ProgressStyle()
+    style = InstanceDict(ProgressStyle).tag(sync=True, **widget_serialization)
 
 
 class _FloatRange(_Float):
@@ -270,16 +259,14 @@ class FloatRangeSlider(_BoundedFloatRange):
         default is '.2f', specifier for the format function used to represent
         slider value for human consumption, modeled after Python 3's format
         specification mini-language (PEP 3101).
-    slider_color : str Unicode color code (eg. '#C13535')
-        color of the slider
-    color : str Unicode color code (eg. '#C13535')
-        color of the value displayed (if readout == True)
     """
     _view_name = Unicode('FloatSliderView').tag(sync=True)
     _model_name = Unicode('FloatSliderModel').tag(sync=True)
     orientation = CaselessStrEnum(values=['horizontal', 'vertical'],
         default_value='horizontal', help="Vertical or horizontal.").tag(sync=True)
     _range = Bool(True, help="Display a range selector").tag(sync=True)
     readout = Bool(True, help="Display the current value of the slider next to it.").tag(sync=True)
-    slider_color = Color(None, allow_none=True).tag(sync=True)
+    readout_format = Unicode('.2f', help="Format for the readout").tag(sync=True)
     continuous_update = Bool(True, help="Update the value of the widget as the user is sliding the slider.").tag(sync=True)
+
+    style = InstanceDict(SliderStyle).tag(sync=True, **widget_serialization)

ipywidgets/widgets/widget_int.py

@@ -12,7 +12,7 @@
 from .widget_core import CoreWidget
 from .widget_style import Style
 from traitlets import Instance
-from .trait_types import Color
+from .trait_types import Color, InstanceDict
 from traitlets import (
     Unicode, CInt, Bool, CaselessStrEnum, Tuple, TraitError, default, validate
 )
@@ -164,11 +164,7 @@ class IntSlider(_BoundedInt):
     readout_format = Unicode('d', help="Format for the readout").tag(sync=True)
     continuous_update = Bool(True, help="Update the value of the widget as the user is holding the slider.").tag(sync=True)
 
-    style = Instance(SliderStyle).tag(sync=True, **widget_serialization)
-
-    @default('style')
-    def _default_style(self):
-        return SliderStyle()
+    style = InstanceDict(SliderStyle).tag(sync=True, **widget_serialization)
 
 
 @register
@@ -192,11 +188,7 @@ class IntProgress(_BoundedInt):
         values=['success', 'info', 'warning', 'danger', ''], default_value='',
         help="""Use a predefined styling for the progess bar.""").tag(sync=True)
 
-    style = Instance(ProgressStyle).tag(sync=True, **widget_serialization)
-
-    @default('style')
-    def _default_style(self):
-        return ProgressStyle()
+    style = InstanceDict(ProgressStyle).tag(sync=True, **widget_serialization)
 
 
 class _IntRange(_Int):
@@ -280,8 +272,8 @@ class IntRangeSlider(_BoundedIntRange):
         default_value='horizontal', help="Vertical or horizontal.").tag(sync=True)
     _range = Bool(True, help="Display a range selector").tag(sync=True)
     readout = Bool(True, help="Display the current value of the slider next to it.").tag(sync=True)
-    slider_color = Color(None, allow_none=True).tag(sync=True)
     continuous_update = Bool(True, help="Update the value of the widget as the user is sliding the slider.").tag(sync=True)
+    style = InstanceDict(SliderStyle).tag(sync=True, **widget_serialization)
 
 
 @register

ipywidgets/widgets/widget_layout.py

@@ -66,6 +66,6 @@ class LayoutTraitType(Instance):
 
     def validate(self, obj, value):
         if isinstance(value, dict):
-            return super(LayoutTraitType, self).validate(obj, Layout(**value))
+            return super(LayoutTraitType, self).validate(obj, self.klass(**value))
         else:
             return super(LayoutTraitType, self).validate(obj, value)