Add input lag reduction test

--HG--
branch : opengl3

code/nel/src/3d/driver/opengl3/driver_opengl.cpp

@@ -690,6 +690,12 @@ bool CDriverGL3::swapBuffers()
 
 	// Check all vertex buffer to see which one are lost
 	updateLostBuffers();
+
+#if NL3D_GL3_SYNC_IMMEDIATE
+	// Sync on the current buffer
+	nlassert(_SwapBufferSync[syncI]);
+	nglClientWaitSync(_SwapBufferSync[syncI], 0, 1000000000ULL);
+#endif
 	
 	// Check in flight buffers, also checks the current one
 	for (size_t i = 0; i < NL3D_GL3_FRAME_QUEUE_MAX; ++i)

code/nel/src/3d/driver/opengl3/driver_opengl.h

@@ -84,6 +84,7 @@ using NLMISC::CVector;
 #define NL3D_GL3_BUFFER_NOT_IN_FLIGHT (std::numeric_limits<uint64>::max())
 #define NL3D_GL3_FRAME_QUEUE_MAX (2) // Maximum is three frames processing (2 frames backlog + current frame)
 #define NL3D_GL3_BUFFER_QUEUE_MAX (NL3D_GL3_FRAME_QUEUE_MAX + 1) // Additional buffer for current working
+#define NL3D_GL3_SYNC_IMMEDIATE 0 // Don't allow frame processing backlog if set to 1. Reduce input lag. Testing only
 
 namespace NL3D {
 namespace NLDRIVERGL3 {