[chaley]

I added the ability to save and restore the GUI pane layout, including Narrow/Wide, what panes show, the pane sizes, and where supported by base calibre the pane positions. The new operations are added to the existing "Layout actions".

Notes:

• You can assign a keyboard shortcut to open the Layout actions menu.
• With the Action chains plugin you can assign shortcuts to specific menu actions such as restoring a layout.
• I included an API for plugin writers to use to save/restore/delete layouts (View manager?). The API methods are documented in calibre.gui2.actions.layout_actions.py.
  
  Spoiler:

      # Public API
      def apply_layout(self, name):
          '''apply_layout()
          Apply a saved GUI panel layout.
  
          :param:`name` The name of the saved layout
  
           Throws KeyError if the name doesn't exist.
          '''
  
      def save_current_layout(self):
          '''save_current_layout()
          Opens a dialog asking for the name to use to save the current layout.
          Saves the current settings under the provided name.
          '''
  
      def current_settings(self):
          '''current_settings()
  
          :return: the current gui layout settings.
          '''
  
      def save_named_layout(self, name, settings):
          '''save_named_layout()
          Saves the settings under the provided name.
  
          :param:`name` The name for the settings.
          :param:`settings`: The gui layout settings to save.
          '''
  
      def delete_layout(self, name, show_warning=True):
          '''delete_layout()
          Delete a saved layout.
  
          :param:`name` The name of the layout to delete
          :param:`show_warning`: If True a warning dialog will be shown before deleting the layout.
          '''
  
      def saved_layout_names(self):
          '''saved_layout_names()
          Get a list of saved layout names
  
          :return: the sorted list of names. The list is empty if there are no names.
          '''

  
  This python template is a small example.
  
  Spoiler:

  python:
  def evaluate(book, context):
  	from calibre.gui2.ui import get_gui
  	gui = get_gui()
  
  	api = gui.iactions['Layout Actions'] # Note the capitalization.
  	settings = api.current_settings()
  	print(settings)
  	names = api.saved_layout_names()
  	print(names)
  	api.apply_layout('Normal')
  	return ', '.join(names)

• While there I added toggling panes to the existing abilities to show and hide panes. All the pane visibility actions are visible in Action chains.
• The changes are in calibre source and will be included in the next calibre release.