From ce73838f1b7a51da81aa731e7d8503011940852a Mon Sep 17 00:00:00 2001
From: Alibek Omarov <a1ba.omarov@gmail.com>
Date: Thu, 4 Jan 2024 05:09:36 +0300
Subject: [PATCH] engine: add a function that validates requested features bits

---
 engine/client/cl_parse.c |  6 +-----
 engine/common/common.h   |  2 +-
 engine/common/host.c     | 32 +++++++++++++++++++++++++++++++-
 engine/server/sv_phys.c  |  6 +++---
 4 files changed, 36 insertions(+), 10 deletions(-)

diff --git a/engine/client/cl_parse.c b/engine/client/cl_parse.c
index 5d15caee..b23a7bf3 100644
--- a/engine/client/cl_parse.c
+++ b/engine/client/cl_parse.c
@@ -903,11 +903,7 @@ void CL_ParseServerData( sizebuf_t *msg, qboolean legacy )
 	Q_strncpy( clgame.maptitle, MSG_ReadString( msg ), sizeof( clgame.maptitle ));
 	background = MSG_ReadOneBit( msg );
 	Q_strncpy( gamefolder, MSG_ReadString( msg ), sizeof( gamefolder ));
-	host.features = (uint)MSG_ReadLong( msg );
-	host.features &= legacy ? ENGINE_LEGACY_FEATURES_MASK : ENGINE_FEATURES_MASK;
-
-	if( !Host_IsLocalGame( ))
-		Host_PrintEngineFeatures( host.features );
+	Host_ValidateEngineFeatures( MSG_ReadDword( msg ));
 
 	if( !legacy )
 	{
diff --git a/engine/common/common.h b/engine/common/common.h
index 8f053788..f6a240e1 100644
--- a/engine/common/common.h
+++ b/engine/common/common.h
@@ -554,7 +554,7 @@ qboolean Host_IsLocalGame( void );
 qboolean Host_IsLocalClient( void );
 void Host_ShutdownServer( void );
 void Host_Error( const char *error, ... ) _format( 1 );
-void Host_PrintEngineFeatures( int features );
+void Host_ValidateEngineFeatures( uint32_t features );
 void Host_Frame( float time );
 void Host_InitDecals( void );
 void Host_Credits( void );
diff --git a/engine/common/host.c b/engine/common/host.c
index e8050fe7..fa7c0410 100644
--- a/engine/common/host.c
+++ b/engine/common/host.c
@@ -190,7 +190,7 @@ void Host_ShutdownServer( void )
 Host_PrintEngineFeatures
 ================
 */
-void Host_PrintEngineFeatures( int features )
+static void Host_PrintEngineFeatures( int features )
 {
 	const char *features_str[] =
 	{
@@ -213,6 +213,36 @@ void Host_PrintEngineFeatures( int features )
 	}
 }
 
+/*
+==============
+Host_ValidateEngineFeatures
+
+validate features bits and set host.features
+==============
+*/
+void Host_ValidateEngineFeatures( uint32_t features )
+{
+	uint32_t mask = ENGINE_FEATURES_MASK;
+
+#if !HOST_DEDICATED
+	if( !Host_IsDedicated( ) && cls.legacymode )
+		mask = ENGINE_LEGACY_FEATURES_MASK;
+#endif
+
+	// don't allow unsupported bits
+	features &= mask;
+
+	// print requested first
+	Host_PrintEngineFeatures( features );
+
+	// now warn about incompatible bits
+	if( FBitSet( features, ENGINE_STEP_POSHISTORY_LERP|ENGINE_COMPUTE_STUDIO_LERP ))
+		Con_Printf( S_WARN "%s: incompatible ENGINE_STEP_POSHISTORY_LERP and ENGINE_COMPUTE_STUDIO_LERP are enabled!\n", __func__ );
+
+	// finally set global variable
+	host.features = features;
+}
+
 /*
 ==============
 Host_IsQuakeCompatible
diff --git a/engine/server/sv_phys.c b/engine/server/sv_phys.c
index 905d81b4..8e152cb4 100644
--- a/engine/server/sv_phys.c
+++ b/engine/server/sv_phys.c
@@ -2139,18 +2139,18 @@ qboolean SV_InitPhysicsAPI( void )
 			if( svgame.physFuncs.SV_CheckFeatures != NULL )
 			{
 				// grab common engine features (it will be shared across the network)
-				host.features = svgame.physFuncs.SV_CheckFeatures() & ENGINE_FEATURES_MASK;
-				Host_PrintEngineFeatures( host.features );
+				Host_ValidateEngineFeatures( svgame.physFuncs.SV_CheckFeatures( ));
 			}
 			return true;
 		}
 
 		// make sure what physic functions is cleared
 		memset( &svgame.physFuncs, 0, sizeof( svgame.physFuncs ));
-
+		Host_ValidateEngineFeatures( 0 );
 		return false; // just tell user about problems
 	}
 
 	// physic interface is missed
+	Host_ValidateEngineFeatures( 0 );
 	return true;
 }