Display : Fix shutdown crashes caused by Python slots

Changes.md

@@ -7,6 +7,7 @@ Fixes
 - GafferTest, GafferImageTest : Fixed import of these modules if the `Gaffer` module had not been imported previously.
 - SceneAlgo : Fixed potential shutdown crashes caused by the adaptor registry [^1].
 - Dispatcher : Fixed shutdown crashes caused by Python slots connected to the dispatch signals [^1].
+- Display : Fixed shutdown crashes caused by Python slots connected to `driverCreatedSignal()` and `imageReceivedSignal()` [^1].
 
 1.4.0.0b5 (relative to 1.4.0.0b4)
 =========

python/GafferImageTest/DisplayTest.py

@@ -319,6 +319,18 @@ def testSetDriver( self ) :
 			driver.close()
 			self.assertTrue( display.driverClosed() )
 
+	def testSignalShutdownCrash( self ) :
+
+		subprocess.check_call( [
+			Gaffer.executablePath(), "env", "python", "-c",
+			"""import GafferImage; GafferImage.Display.driverCreatedSignal().connect( lambda d, p : None, scoped = False )"""
+		] )
+
+		subprocess.check_call( [
+			Gaffer.executablePath(), "env", "python", "-c",
+			"""import GafferImage; GafferImage.Display.imageReceivedSignal().connect( lambda p : None, scoped = False )"""
+		] )
+
 	def __testTransferImage( self, fileName ) :
 
 		imageReader = GafferImage.ImageReader()

src/GafferImage/Display.cpp

@@ -466,14 +466,14 @@ void Display::affects( const Gaffer::Plug *input, AffectedPlugsContainer &output
 
 Display::DriverCreatedSignal &Display::driverCreatedSignal()
 {
-	static DriverCreatedSignal s;
-	return s;
+	static DriverCreatedSignal *g_driverCreatedSignal = new DriverCreatedSignal;
+	return *g_driverCreatedSignal;
 }
 
 Node::UnaryPlugSignal &Display::imageReceivedSignal()
 {
-	static UnaryPlugSignal s;
-	return s;
+	static UnaryPlugSignal *g_imageReceivedSignal = new UnaryPlugSignal;
+	return *g_imageReceivedSignal;
 }
 
 void Display::setDriver( IECoreImage::DisplayDriverPtr driver, bool copy )