[#2691] Fixes regarding previewing config options

* Moved to the helpers function, as on the module root config options
  weren't yet set.
* Define default values, otherwise instances using old ini files won't
  get any format preview
* Namespace config options ("ckan.preview...")
* Add documentation about the config options

ckan/config/deployment.ini_tmpl

@@ -241,8 +241,8 @@ ckan.feeds.author_link =
 #
 # Set the file types that should be previewed inline (e.g. images) or directly in an iframe.
 
-preview.direct = png jpg gif
-preview.loadable = html htm rdf+xml owl+xml xml n3 n-triples turtle plain atom csv tsv rss txt json
+ckan.preview.direct = png jpg gif
+ckan.preview.loadable = html htm rdf+xml owl+xml xml n3 n-triples turtle plain atom csv tsv rss txt json
 
 # Activity Streams
 #

ckan/lib/datapreview.py

@@ -11,9 +11,8 @@
 
 import ckan.plugins as p
 
-
-direct_embed = config.get('preview.direct', '').split(' ')
-loadable_in_iframe = config.get('preview.loadable', '').split(' ')
+DEFAULT_DIRECT_EMBED = ['png', 'jpg', 'gif']
+DEFAULT_LOADABLE_IFRAME = ['html', 'htm', 'rdf+xml', 'owl+xml', 'xml', 'n3', 'n-triples', 'turtle', 'plain', 'atom', 'csv', 'tsv', 'rss', 'txt', 'json']
 
 
 def compare_domains(urls):

ckan/lib/helpers.py

@@ -1394,14 +1394,20 @@ def resource_preview(resource, pkg_id):
             resource_type=format_lower,
             reason='No valid resource url has been defined.'
             )
+    direct_embed = config.get('ckan.preview.direct', '').split()
+    if not direct_embed:
+        direct_embed = datapreview.DEFAULT_DIRECT_EMBED
+    loadable_in_iframe = config.get('ckan.preview.loadable', '').split()
+    if not loadable_in_iframe:
+        loadable_in_iframe = datapreview.DEFAULT_LOADABLE_IFRAME
 
     if datapreview.can_be_previewed(data_dict):
         url = url_for(controller='package', action='resource_datapreview',
             resource_id=resource['id'], id=pkg_id, qualified=True)
-    elif format_lower in datapreview.direct_embed:
+    elif format_lower in direct_embed:
         directly = True
         url = resource['url']
-    elif format_lower in datapreview.loadable_in_iframe:
+    elif format_lower in loadable_in_iframe:
         url = resource['url']
     else:
         log.info('No preview handler for resource type {0}'.format(format_lower))

doc/configuration.rst

@@ -192,6 +192,27 @@ Default value:  ``20``
 
 This controls the pagination of the dataset search results page. This is the maximum number of datasets viewed per page of results.
 
+ckan.preview.direct
+^^^^^^^^^^^^^^^^^^^
+
+Example::
+ ckan.preview.direct = png jpg gif
+
+Default value: ``png jpg gif``
+
+Defines the resource formats which should be embedded directly in an `img` tag
+when previewing them.
+
+ckan.preview.loadable
+^^^^^^^^^^^^^^^^^^^^^
+
+Example::
+ ckan.preview.loadable = html htm rdf+xml owl+xml xml n3 n-triples turtle plain atom csv tsv rss txt json
+
+Default value: ``html htm rdf+xml owl+xml xml n3 n-triples turtle plain atom csv tsv rss txt json``
+
+Defines the resource formats which should be loaded directly in an `iframe`
+tag when previewing them.
 
 Authentication Settings
 -----------------------