Content plugin: node view modes

Creating this feature request based on a comment by ausnahmezustand over on #1397676: Support for Views with contextual filter.

In addition to the Field and View data sources that are available now, the different view modes of the node itself should also be available as the content of a subpage. This would allow site admins to make use of Display Suite to configure different view modes for the content type—displaying different fields in different regions in each view mode—and use those for the subpages.

Implementing this will require some structural changes to the module: the list of data sources (when adding/editing a subpage on a content type) and the content used for a subpage are handled in node_subpages. Support for Views and Fields are coded right into node_subpages_add_subpage() and node_subpages_view(), but instead, these functions should be invoking hooks to allow other modules to supply a list of potential data sources, and to supply the content for a subpage. node_subpages will then implement these hooks (always eat your own dog food!) to provide the existing Field and Views support.

Todo:

• Add a source_module column to the node_subpages table. This will store the name of the module providing the data for the subpage. Also need an update function to add this column to existing installs.
• In node_subpages_add_subpage(), invoke hook_node_subpages_data_sources to get a list of data sources. Modules implementing this hook should provide:
  • Module name
  • Data types provded (field, views, node_view_mode, etc)
  • List of sources for each data type (list of fields, list of views, list of view modes, etc)

  When the admin chooses their data source, the three values will be stored in the node_subpages table.

• Implement hook_node_subpages_data_sources() in the node_subpages and move the Fields and Views support into that function (from node_subpages_add_subpage())
• In node_subpages_view(), invoke hook_node_subpages_content on the module that provides the data source selected for the subpage. This hook should return a render array.
• Implement hook_node_subpages_content in node_subpages, and move the current Fields and Views logic to that function from node_subpages_view().

Adding these hooks will allow other contrib modules to add data sources for subpages, if other people are interested in doing so, and can be used to add support for view modes:

• Create a new node_subpages_ds module to contain this functionality. It will list Display Suite as a dependency.
• Implement hook_node_subpages_data_sources and hook_node_subpages_content in the new node_subpages_ds module. The site admin will be able to select any view mode to use when making use of the view mode data source.