Update DisplayDriverServer and ClientDisplayDriver

Adds option to server and client driver to allow a 'merge' driver
that shares a display driver to write to.

Author: Linas Beresna

src/IECoreImage/ClientDisplayDriver.cpp

@@ -92,6 +92,7 @@ ClientDisplayDriver::ClientDisplayDriver( const Imath::Box2i &displayWindow, con
 	// expects three custom StringData parameters : displayHost, displayPort and displayType
 	const StringData *displayHostData = parameters->member<StringData>( "displayHost", true /* throw if missing */ );
 	const StringData *displayPortData = parameters->member<StringData>( "displayPort", true /* throw if missing */ );
+	const BoolData *mergeDriverData = parameters->member<BoolData>( "mergeDriver", false /* throw if missing */ );
 
 	m_data->m_host = displayHostData->readable();
 	m_data->m_port = displayPortData->readable();
@@ -122,11 +123,19 @@ ClientDisplayDriver::ClientDisplayDriver( const Imath::Box2i &displayWindow, con
 	StringVectorDataPtr channelNamesData = new StringVectorData( channelNames );
 
 	IECore::CompoundDataPtr tmpParameters = parameters->copy();
+	if (mergeDriverData && mergeDriverData->readable())
+	{
+		const IntData *sessionIdData = parameters->member<IntData>( "sessionId", true /* throw if missing */ );
+		tmpParameters->writable()[ "clientPID" ] = new IntData( sessionIdData->readable() );
+	}
+	else
+	{
 #ifndef _MSC_VER
-	tmpParameters->writable()[ "clientPID" ] = new IntData( getpid() );
+		tmpParameters->writable()[ "clientPID" ] = new IntData( getpid() );
 #else
-	tmpParameters->writable()[ "clientPID" ] = new IntData( _getpid() );
+		tmpParameters->writable()[ "clientPID" ] = new IntData( _getpid() );
 #endif
+	}
 
 	// build the data block
 	io = new MemoryIndexedIO( ConstCharVectorDataPtr(), IndexedIO::rootPath, IndexedIO::Exclusive | IndexedIO::Write );

src/IECoreImage/DisplayDriverServer.cpp

@@ -53,6 +53,8 @@
 #include "boost/bind/bind.hpp"
 
 #include <thread>
+#include <map>
+#include <utility>
 
 #include <fcntl.h>
 #ifndef _MSC_VER
@@ -70,6 +72,8 @@ IE_CORE_DEFINERUNTIMETYPED( DisplayDriverServer );
 namespace
 {
 
+std::map<int, std::pair<DisplayDriverPtr, int>> mergeMap;
+
 /* Set the FD_CLOEXEC flag for the given socket descriptor, so that it will not exist on child processes.*/
 static void fixSocketFlags( int socketDesc )
 {
@@ -114,6 +118,8 @@ class DisplayDriverServer::Session : public RefCounted
 		DisplayDriverPtr m_displayDriver;
 		DisplayDriverServerHeader m_header;
 		CharVectorDataPtr m_buffer;
+		bool m_mergeSession;
+		int m_mergeId;
 };
 
 class DisplayDriverServer::PrivateData : public RefCounted
@@ -293,7 +299,7 @@ void DisplayDriverServer::handleAccept( DisplayDriverServer::SessionPtr session,
  */
 
 DisplayDriverServer::Session::Session( boost::asio::io_service& io_service ) :
-	m_socket( io_service ), m_displayDriver(nullptr), m_buffer( new CharVectorData( ) )
+	m_socket( io_service ), m_displayDriver(nullptr), m_buffer( new CharVectorData( ) ), m_mergeSession(false), m_mergeId(-1)
 {
 }
 
@@ -363,7 +369,15 @@ void DisplayDriverServer::Session::handleReadHeader( const boost::system::error_
 		{
 			try
 			{
-				m_displayDriver->imageClose();
+				if ( !m_mergeSession )
+				{
+					m_displayDriver->imageClose();
+				}
+				else if ( auto search = mergeMap.find(m_mergeId); search != mergeMap.end() && --mergeMap[m_mergeId].second <= 0 )
+				{
+					mergeMap.erase(m_mergeId);
+					m_displayDriver->imageClose();
+				}
 			}
 			catch ( std::exception &e )
 			{
@@ -423,9 +437,39 @@ void DisplayDriverServer::Session::handleReadOpenParameters( const boost::system
 
 		const StringData *displayType = parameters->member<StringData>( "remoteDisplayType", true /* throw if missing */ );
 
+		const BoolData *mergeDriverData = parameters->member<BoolData>( "mergeDriver", false);
+        m_mergeSession = mergeDriverData && mergeDriverData->readable();
+
 		// create a displayDriver using the factory function.
-		m_displayDriver = DisplayDriver::create( displayType->readable(), displayWindow->readable(), dataWindow->readable(), channelNames->readable(), parameters );
+		if (!m_mergeSession)
+		{
+			m_displayDriver = DisplayDriver::create( displayType->readable(), displayWindow->readable(), dataWindow->readable(), channelNames->readable(), parameters );
+		}
+		else
+		{
+			m_mergeId = parameters->member<IntData>( "sessionId", true /* throw if missing */ )->readable();
 
+			// Check if merge ID in map, if not then create display driver and session count pair with merge ID.
+			if (const auto search = mergeMap.find(m_mergeId); search == mergeMap.end())
+			{
+				const IntData *sessionClientsData = parameters->member<IntData>( "sessionClients", true /* throw if missing */ );
+				mergeMap.emplace(
+						m_mergeId,
+						std::make_pair(
+							DisplayDriver::create(
+								displayType->readable(),
+								displayWindow->readable(),
+								displayWindow->readable(), // For merge we want dataWindow = displayWindow
+								channelNames->readable(),
+								parameters
+								),
+							sessionClientsData->readable()
+							)
+						);
+			}
+			// Merge ID is now in map, so load the display driver.
+			m_displayDriver = mergeMap[m_mergeId].first;
+		}
 		scanLineOrder = m_displayDriver->scanLineOrderOnly();
 		acceptsRepeatedData = m_displayDriver->acceptsRepeatedData();
 	}