old_contents: # Enthought library imports.
  from enthought.traits.api import Bool, Enum, HasTraits, Str, Tuple
  
  # Local imports.
  from i_task_pane import ITaskPane
  
  
  class IDockPane(ITaskPane):
      """ A pane that is useful but unessential for a task.
  
      Dock panes are arranged around the central pane in dock areas, and can, in
      general, be moved, resized, and hidden by the user.
      """
  
      # If enabled, the pane will have a button to close it, and a visibility
      # toggle button will be added to the View menu. Otherwise, the pane's
      # visibility will only be adjustable programmatically, though the 'visible'
      # attribute.
      closable = Bool(True)
  
      # The dock area in which the pane is currently present.
      dock_area = Enum('left', 'right', 'top', 'bottom')
  
      # Whether the pane can be detached from the main window.
      floatable = Bool(True)
  
      # Whether the pane is currently detached from the main window.
      floating = Bool(False)
  
      # Whether the pane can be moved from one dock area to another.
      movable = Bool(True)
  
      # The size of the dock pane. Note that this value is read-only.
      size = Tuple
  
      # Whether the pane is currently visible.
      visible = Bool(True)
  
      ###########################################################################
      # 'IDockPane' interface.
      ###########################################################################
  
      def create_contents(self, parent):
          """ Create and return the toolkit-specific contents of the dock pane.
          """
  
      def hide(self):
          """ Convenience method to hide the dock pane.
          """
  
      def show(self):
          """ Convenience method to show the dock pane.
          """
  
  
  class MDockPane(HasTraits):
      """ Mixin containing common code for toolkit-specific implementations.
      """
  
      #### 'IDockPane' interface ################################################
  
      closable = Bool(True)
      dock_area = Enum('left', 'right', 'top', 'bottom')
      floatable = Bool(True)
      floating = Bool(False)
      movable = Bool(True)
      size = Tuple
      visible = Bool(True)
  
      ###########################################################################
      # 'IDockPane' interface.
      ###########################################################################
  
      def hide(self):
          """ Convenience method to hide the dock pane.
          """
          self.visible = False
  
      def show(self):
          """ Convenience method to show the dock pane.
          """
          self.visible = True
  
new_contents: # Enthought library imports.
  from enthought.traits.api import Bool, Enum, HasTraits, Str, Tuple
  
  # Local imports.
  from i_task_pane import ITaskPane
  
  
  class IDockPane(ITaskPane):
      """ A pane that is useful but unessential for a task.
  
      Dock panes are arranged around the central pane in dock areas, and can, in
      general, be moved, resized, and hidden by the user.
      """
  
      # If enabled, the pane will have a button to close it, and a visibility
      # toggle button will be added to the View menu. Otherwise, the pane's
      # visibility will only be adjustable programmatically, though the 'visible'
      # attribute.
      closable = Bool(True)
  
      # The dock area in which the pane is currently present.
      dock_area = Enum('left', 'right', 'top', 'bottom')
  
      # Whether the pane can be detached from the main window.
      floatable = Bool(True)
  
      # Whether the pane is currently detached from the main window.
      floating = Bool(False)
  
      # Whether the pane can be moved from one dock area to another.
      movable = Bool(True)
  
      # The size of the dock pane. Note that this value is read-only.
      size = Tuple
  
      # Whether the pane is currently visible.
      visible = Bool(False)
  
      ###########################################################################
      # 'IDockPane' interface.
      ###########################################################################
  
      def create_contents(self, parent):
          """ Create and return the toolkit-specific contents of the dock pane.
          """
  
      def hide(self):
          """ Convenience method to hide the dock pane.
          """
  
      def show(self):
          """ Convenience method to show the dock pane.
          """
  
  
  class MDockPane(HasTraits):
      """ Mixin containing common code for toolkit-specific implementations.
      """
  
      #### 'IDockPane' interface ################################################
  
      closable = Bool(True)
      dock_area = Enum('left', 'right', 'top', 'bottom')
      floatable = Bool(True)
      floating = Bool(False)
      movable = Bool(True)
      size = Tuple
      visible = Bool(False)
  
      ###########################################################################
      # 'IDockPane' interface.
      ###########################################################################
  
      def hide(self):
          """ Convenience method to hide the dock pane.
          """
          self.visible = False
  
      def show(self):
          """ Convenience method to show the dock pane.
          """
          self.visible = True
  
subject: Fix default value of DockPane's 'visible' attribute.