Simplify/Robustify the thumbnail URL usage in templates

So far templates required a very complex blurb to simply insert a
thumbnail URL, exposing much of the internal logic to the template
designer. In addition, we would fail with an error if for some
reason the media_files['thumb'] entry was never populated.

This adds the MediaEntry.thumb_url property that template designers
can simply use. It will do the right thing, either fetching the proper
thumbnail or hand back a generic icon specified in a media's
MEDIA_MANAGER as "default_thumb".

Add an image default fallback icon (stolen from Tangos, which are
Public Domain since version 0.8.90 as I understand) since the one
we referred to was not existing. Perhaps, a "broken image" icon
would be better, but I'll leave that to our capable designers.

All templates have been modified to make use of the new thumb_url
function.

Signed-off-by: Sebastian Spaeth <Sebastian@SSpaeth.de>

mediagoblin/db/mixin.py

@@ -27,6 +27,8 @@ These functions now live here and get "mixed in" into the
 real objects.
 """
 
+import importlib
+
 from mediagoblin import mg_globals
 from mediagoblin.auth import lib as auth_lib
 from mediagoblin.tools import common, licenses
@@ -112,6 +114,23 @@ class MediaEntryMixin(object):
             media=self.slug_or_id,
             **extra_args)
 
+    @property
+    def thumb_url(self):
+        """Return the thumbnail URL (for usage in templates)
+        Will return either the real thumbnail or a default fallback icon."""
+        # TODO: implement generic fallback in case MEDIA_MANAGER does
+        # not specify one?
+        if u'thumb' in self.media_files:
+            thumb_url = mg_globals.app.public_store.file_url(
+                            self.media_files[u'thumb'])
+        else:
+            # no thumbnail in media available. Get the media's
+            # MEDIA_MANAGER for the fallback icon and return static URL
+            manager = importlib.import_module(self.media_type)
+            thumb_url = manager.MEDIA_MANAGER[u'default_thumb']
+            thumb_url = mg_globals.app.staticdirector(thumb_url) # use static
+        return thumb_url
+
     def get_fail_exception(self):
         """
         Get the exception that's appropriate for this error

mediagoblin/media_types/image/__init__.py

@@ -24,5 +24,5 @@ MEDIA_MANAGER = {
                                 # 'mediagoblin.media_types.image.processing'?
     "sniff_handler": sniff_handler,
     "display_template": "mediagoblin/media_displays/image.html",
-    "default_thumb": "images/media_thumbs/image.jpg",
+    "default_thumb": "images/media_thumbs/image.png",
     "accepted_extensions": ["jpg", "jpeg", "png", "gif", "tiff"]}

mediagoblin/templates/mediagoblin/edit/attachments.html

@@ -36,8 +36,7 @@
           Editing attachments for {{ media_title }}
         {%- endtrans %}</h1>
       <div style="text-align: center;" >
-        <img src="{{ request.app.public_store.file_url(
-                         media.media_files['thumb']) }}" />
+        <img src="{{ media.thumb_url }}" />
       </div>
 
       {% if media.attachment_files|count %}

mediagoblin/templates/mediagoblin/edit/edit.html

@@ -34,8 +34,7 @@
     <div class="form_box_xl edit_box">
       <h1>{% trans media_title=media.title %}Editing {{ media_title }}{% endtrans %}</h1>
       <div style="text-align: center;" >
-        <img src="{{ request.app.public_store.file_url(
-                         media.media_files['thumb']) }}" />
+        <img src="{{ media.thumb_url }}" />
       </div>
       {{ wtforms_util.render_divs(form) }}
       <div class="form_submit_buttons">

mediagoblin/templates/mediagoblin/user_pages/collection_item_confirm_remove.html

@@ -35,8 +35,7 @@
       </h1>
 
       <div style="text-align: center;" >
-        <img src="{{ request.app.public_store.file_url(
-                         collection_item.get_media_entry.media_files['thumb']) }}" />
+        <img src="{{ collection_item.get_media_entry.thumb_url }}" />
       </div>
 
       <br />

mediagoblin/templates/mediagoblin/user_pages/media_collect.html

@@ -38,8 +38,7 @@
       </h1>
 
       <div style="text-align: center;" >
-        <img src="{{ request.app.public_store.file_url(
-                         media.media_files['thumb']) }}" />
+        <img src="{{ media.thumb_url }}" />
       </div>
 
       <br />

mediagoblin/templates/mediagoblin/user_pages/media_confirm_delete.html

@@ -33,8 +33,7 @@
       </h1>
 
       <div style="text-align: center;" >
-        <img src="{{ request.app.public_store.file_url(
-                         media.media_files['thumb']) }}" />
+        <img src="{{ media.thumb_url }}" />
       </div>
 
       <br />

mediagoblin/templates/mediagoblin/utils/collection_gallery.html

@@ -31,8 +31,7 @@
                      {%- if loop.first %} thumb_entry_first
                      {%- elif loop.last %} thumb_entry_last{% endif %}">
             <a href="{{ entry_url }}">
-              <img src="{{ request.app.public_store.file_url(
-                             media_entry.media_files['thumb']) }}" />
+              <img src="{{ media_entry.thumb_url }}" />
             </a>
 
             {% if item.note %}

mediagoblin/templates/mediagoblin/utils/object_gallery.html

@@ -30,8 +30,7 @@
                      {%- if loop.first %} thumb_entry_first
                      {%- elif loop.last %} thumb_entry_last{% endif %}">
             <a href="{{ entry_url }}">
-              <img src="{{ request.app.public_store.file_url(
-                             entry.media_files['thumb']) }}" />
+              <img src="{{ entry.thumb_url }}" />
             </a>
             {% if entry.title %}
               <a class="thumb_entry_title" href="{{ entry_url }}">{{ entry.title }}</a>