[telepathy-gabble/master] Add a data-driven function to fall back through possible implementations

[Simon McVittie]

This is useful to pick a Jingle transport or a Jingle content type, for
instance.
---
 src/presence.c |   30 ++++++++++++++++++++++++++++++
 src/presence.h |   11 +++++++++++
 2 files changed, 41 insertions(+), 0 deletions(-)

diff --git a/src/presence.c b/src/presence.c
index 7b07c69..64e266f 100644
--- a/src/presence.c
+++ b/src/presence.c
@@ -600,3 +600,33 @@ gabble_presence_removed_from_view (GabblePresence *self)
   g_free (old_status_message);
   return ret;
 }
+
+gpointer
+gabble_presence_resource_pick_best_feature (GabblePresence *presence,
+    const gchar *resource,
+    const GabbleFeatureFallback *table,
+    GabbleCapabilitySetPredicate predicate)
+{
+  Resource *res;
+  const GabbleFeatureFallback *row;
+
+  g_return_val_if_fail (presence != NULL, NULL);
+  g_return_val_if_fail (resource != NULL, NULL);
+  g_return_val_if_fail (predicate != NULL, NULL);
+  g_return_val_if_fail (table != NULL, NULL);
+
+  res = _find_resource (presence, resource);
+
+  if (res == NULL)
+    return NULL;
+
+  for (row = table; row->result != NULL; row++)
+    {
+      if (row->considered && predicate (res->cap_set, row->check_data))
+        {
+          return row->result;
+        }
+    }
+
+  return NULL;
+}
diff --git a/src/presence.h b/src/presence.h
index fa710e5..976a7fc 100644
--- a/src/presence.h
+++ b/src/presence.h
@@ -101,6 +101,17 @@ gchar *gabble_presence_dump (GabblePresence *presence);
 gboolean gabble_presence_added_to_view (GabblePresence *presence);
 gboolean gabble_presence_removed_from_view (GabblePresence *presence);
 
+/* Data-driven feature fallback */
+typedef struct {
+    gboolean considered;
+    gpointer check_data;
+    gpointer result;
+} GabbleFeatureFallback;
+gpointer gabble_presence_resource_pick_best_feature (GabblePresence *presence,
+    const gchar *resource,
+    const GabbleFeatureFallback *table,
+    GabbleCapabilitySetPredicate predicate);
+
 G_END_DECLS
 
 #endif /* __GABBLE_PRESENCE_H__ */
-- 
1.5.6.5