From 7b1056b9467673d004ea7dd63ad91461b8f616fa Mon Sep 17 00:00:00 2001
From: Julien Isorce <jisorce@oblong.com>
Date: Mon, 18 Sep 2017 17:06:32 +0100
Subject: [PATCH] appsink: also clear preroll buffer in _pull_sample

If someone calls gst_app_sink_try_pull_sample they are
probably no longer interested in any preroll samples.

Useful if the user has not registered a preroll appsink callback.

Also added unit test 'test_do_not_care_preroll'
  make elements/appsink.check
that fails without this patch.

https://bugzilla.gnome.org/show_bug.cgi?id=786740
---
 gst-libs/gst/app/gstappsink.c  |  1 +
 tests/check/elements/appsink.c | 26 ++++++++++++++++++++++++++
 2 files changed, 27 insertions(+)

diff --git a/gst-libs/gst/app/gstappsink.c b/gst-libs/gst/app/gstappsink.c
index 539d9b05b6..70a3d79302 100644
--- a/gst-libs/gst/app/gstappsink.c
+++ b/gst-libs/gst/app/gstappsink.c
@@ -1556,6 +1556,7 @@ gst_app_sink_try_pull_sample (GstAppSink * appsink, GstClockTime timeout)
   priv = appsink->priv;
 
   g_mutex_lock (&priv->mutex);
+  gst_buffer_replace (&priv->preroll_buffer, NULL);
 
   while (TRUE) {
     GST_DEBUG_OBJECT (appsink, "trying to grab a buffer");
diff --git a/tests/check/elements/appsink.c b/tests/check/elements/appsink.c
index 84a9f829ce..c3547ee068 100644
--- a/tests/check/elements/appsink.c
+++ b/tests/check/elements/appsink.c
@@ -528,6 +528,31 @@ GST_START_TEST (test_pull_preroll)
 
 GST_END_TEST;
 
+GST_START_TEST (test_do_not_care_preroll)
+{
+  GstElement *sink = NULL;
+  GstBuffer *buffer = NULL;
+  GstSample *pulled_sample = NULL;
+
+  sink = setup_appsink ();
+
+  ASSERT_SET_STATE (sink, GST_STATE_PLAYING, GST_STATE_CHANGE_ASYNC);
+
+  buffer = gst_buffer_new_and_alloc (4);
+  fail_unless (gst_pad_push (mysrcpad, buffer) == GST_FLOW_OK);
+
+  pulled_sample = gst_app_sink_pull_sample (GST_APP_SINK (sink));
+  fail_unless (pulled_sample);
+  gst_sample_unref (pulled_sample);
+
+  fail_if (gst_app_sink_try_pull_preroll (GST_APP_SINK (sink), 0));
+
+  ASSERT_SET_STATE (sink, GST_STATE_NULL, GST_STATE_CHANGE_SUCCESS);
+  cleanup_appsink (sink);
+}
+
+GST_END_TEST;
+
 static Suite *
 appsink_suite (void)
 {
@@ -546,6 +571,7 @@ appsink_suite (void)
   tcase_add_test (tc_chain, test_segment);
   tcase_add_test (tc_chain, test_pull_with_timeout);
   tcase_add_test (tc_chain, test_pull_preroll);
+  tcase_add_test (tc_chain, test_do_not_care_preroll);
 
   return s;
 }