From ac09ae7d73f394e99cbdf132a67ce1b8e9b0ffb4 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Sebastian=20Dr=C3=B6ge?= <sebastian@centricular.com>
Date: Mon, 4 Dec 2017 21:45:03 +0200
Subject: [PATCH] Never fail downwards state changes

This causes bugs in GStreamer and leads to crashes and deadlocks
---
 gst-plugin/src/element.rs | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/gst-plugin/src/element.rs b/gst-plugin/src/element.rs
index 7b764804..05d60b84 100644
--- a/gst-plugin/src/element.rs
+++ b/gst-plugin/src/element.rs
@@ -243,8 +243,18 @@ where
     let wrap: T = from_glib_borrow(ptr as *mut InstanceStruct<T>);
     let imp = &*element.imp;
 
-    panic_to_error!(&wrap, &element.panicked, gst::StateChangeReturn::Failure, {
-        imp.change_state(&wrap, from_glib(transition))
+    // *Never* fail downwards state changes, this causes bugs in GStreamer
+    // and leads to crashes and deadlocks.
+    let transition = from_glib(transition);
+    let fallback = match transition {
+        gst::StateChange::PlayingToPaused
+        | gst::StateChange::PausedToReady
+        | gst::StateChange::ReadyToNull => gst::StateChangeReturn::Success,
+        _ => gst::StateChangeReturn::Failure,
+    };
+
+    panic_to_error!(&wrap, &element.panicked, fallback, {
+        imp.change_state(&wrap, transition)
     }).to_glib()
 }