pad: implement a default recursive-accept-caps handler

The handler will act similar to the default accept-caps one.

If it is a proxy pad, will proxy the query and, if accepted, then compare
with the pad template. Otherwise does a caps query and uses
gst_caps_is_subset() to check if the caps would be acceptable.

is_subset() is always used in this case because it is more restrictive
than an intersect, even if a pad is marked with ACCEPT_INTERSECT flag
it might be that one of the downstream pads aren't intersect and would
use is_subset() so always default to subset checks when a downstream
query was made.

4 files changed, 115 insertions, 0 deletions

diff --git a/gst/gstpad.c b/gst/gstpad.c
index f9822ea55..d14d3e867 100644
--- a/gst/gstpad.c
+++ b/gst/gstpad.c
@@ -3076,6 +3076,59 @@ done:
   return TRUE;
 }
 
+/* Default recursive accept caps implementation just checks against
+ * the allowed caps for the pad */
+static gboolean
+gst_pad_query_recursive_accept_caps_default (GstPad * pad, GstQuery * query)
+{
+  /* get the caps and see if it intersects to something not empty */
+  GstCaps *caps, *allowed = NULL;
+  gboolean result;
+  gboolean allowed_is_template = FALSE;
+
+  GST_DEBUG_OBJECT (pad, "query recursive-accept-caps %" GST_PTR_FORMAT, query);
+
+  /* first forward the query to internally linked pads when we are dealing with
+   * a PROXY CAPS */
+  if (GST_PAD_IS_PROXY_CAPS (pad)) {
+    result = gst_pad_proxy_query_recursive_accept_caps (pad, query);
+    if (result) {
+      allowed = gst_pad_get_pad_template_caps (pad);
+      allowed_is_template = TRUE;
+    } else
+      goto done;
+  }
+
+  gst_query_parse_recursive_accept_caps (query, &caps);
+  if (!allowed) {
+    GST_CAT_DEBUG_OBJECT (GST_CAT_PERFORMANCE, pad,
+        "fallback RECURSIVE_ACCEPT_CAPS query, consider implementing a specialized version");
+    allowed = gst_pad_query_caps (pad, caps);
+  }
+
+  if (allowed) {
+    if (allowed_is_template && GST_PAD_IS_ACCEPT_INTERSECT (pad)) {
+      GST_DEBUG_OBJECT (pad,
+          "allowed caps intersect %" GST_PTR_FORMAT ", caps %" GST_PTR_FORMAT,
+          allowed, caps);
+      result = gst_caps_can_intersect (caps, allowed);
+    } else {
+      GST_DEBUG_OBJECT (pad, "allowed caps subset %" GST_PTR_FORMAT ", caps %"
+          GST_PTR_FORMAT, allowed, caps);
+      result = gst_caps_is_subset (caps, allowed);
+    }
+    gst_caps_unref (allowed);
+  } else {
+    GST_DEBUG_OBJECT (pad, "no compatible caps allowed on the pad");
+    result = FALSE;
+  }
+  gst_query_set_recursive_accept_caps_result (query, result);
+
+done:
+  return TRUE;
+}
+
+
 /* Default caps implementation */
 static gboolean
 gst_pad_query_caps_default (GstPad * pad, GstQuery * query)
@@ -3320,6 +3373,10 @@ gst_pad_query_default (GstPad * pad, GstObject * parent, GstQuery * query)
       ret = gst_pad_query_caps_default (pad, query);
       forward = FALSE;
       break;
+    case GST_QUERY_RECURSIVE_ACCEPT_CAPS:
+      ret = gst_pad_query_recursive_accept_caps_default (pad, query);
+      forward = FALSE;
+      break;
     case GST_QUERY_LATENCY:
       ret = gst_pad_query_latency_default (pad, query);
       forward = FALSE;
diff --git a/gst/gstutils.c b/gst/gstutils.c
index 076de1ca6..43340e5e5 100644
--- a/gst/gstutils.c
+++ b/gst/gstutils.c
@@ -2543,6 +2543,62 @@ gst_pad_proxy_query_accept_caps (GstPad * pad, GstQuery * query)
   return data.ret;
 }
 
+static gboolean
+query_recursive_accept_caps_func (GstPad * pad, QueryAcceptCapsData * data)
+{
+  if (G_LIKELY (gst_pad_peer_query (pad, data->query))) {
+    gboolean result;
+
+    gst_query_parse_recursive_accept_caps_result (data->query, &result);
+    data->ret &= result;
+  }
+  return FALSE;
+}
+
+/**
+ * gst_pad_proxy_query_recursive_accept_caps:
+ * @pad: a #GstPad to proxy.
+ * @query: an RECURSIVE_ACCEPT_CAPS #GstQuery.
+ *
+ * Checks if all internally linked pads of @pad accepts the caps in @query and
+ * returns the intersection of the results.
+ *
+ * This function is useful as a default recursive accept caps query
+ * function for an element that can handle any stream format,
+ * but requires caps that are acceptable for all opposite pads.
+ *
+ * Returns: %TRUE if @query could be executed
+ * Since: 1.8
+ */
+gboolean
+gst_pad_proxy_query_recursive_accept_caps (GstPad * pad, GstQuery * query)
+{
+  QueryAcceptCapsData data;
+
+  g_return_val_if_fail (GST_IS_PAD (pad), FALSE);
+  g_return_val_if_fail (GST_IS_QUERY (query), FALSE);
+  g_return_val_if_fail (GST_QUERY_TYPE (query) ==
+      GST_QUERY_RECURSIVE_ACCEPT_CAPS, FALSE);
+
+  GST_CAT_DEBUG_OBJECT (GST_CAT_PADS, pad,
+      "proxying recursive accept caps query for %s:%s",
+      GST_DEBUG_PAD_NAME (pad));
+
+  data.query = query;
+  /* value to hold the return, by default it holds TRUE */
+  /* FIXME: TRUE is wrong when there are no pads */
+  data.ret = TRUE;
+
+  gst_pad_forward (pad,
+      (GstPadForwardFunction) query_recursive_accept_caps_func, &data);
+  gst_query_set_recursive_accept_caps_result (query, data.ret);
+
+  GST_CAT_DEBUG_OBJECT (GST_CAT_PADS, pad,
+      "proxying recursive accept caps query: %d", data.ret);
+
+  return data.ret;
+}
+
 typedef struct
 {
   GstQuery *query;
diff --git a/gst/gstutils.h b/gst/gstutils.h
index 457a76a0f..a929d8458 100644
--- a/gst/gstutils.h
+++ b/gst/gstutils.h
@@ -915,6 +915,7 @@ GstElement*             gst_pad_get_parent_element      (GstPad *pad);
 
 /* util query functions */
 gboolean                gst_pad_proxy_query_accept_caps (GstPad *pad, GstQuery *query);
+gboolean                gst_pad_proxy_query_recursive_accept_caps (GstPad *pad, GstQuery *query);
 gboolean                gst_pad_proxy_query_caps        (GstPad *pad, GstQuery *query);
 
 gboolean                gst_pad_query_position          (GstPad *pad, GstFormat format, gint64 *cur);
diff --git a/win32/common/libgstreamer.def b/win32/common/libgstreamer.def
index 196b158e6..933f56960 100644
--- a/win32/common/libgstreamer.def
+++ b/win32/common/libgstreamer.def
@@ -880,6 +880,7 @@ EXPORTS
 	gst_pad_probe_type_get_type
 	gst_pad_proxy_query_accept_caps
 	gst_pad_proxy_query_caps
+	gst_pad_proxy_query_recursive_accept_caps
 	gst_pad_pull_range
 	gst_pad_push
 	gst_pad_push_event