Allow observe for dying player with EF_NODRAW effect

regamedll/dlls/observer.cpp

@@ -29,9 +29,29 @@ CBasePlayer *CBasePlayer::__API_HOOK(Observer_IsValidTarget)(int iPlayerIndex, b
 	CBasePlayer *pPlayer = UTIL_PlayerByIndex(iPlayerIndex);
 
 	// Don't spec observers or players who haven't picked a class yet
-	if (!pPlayer || pPlayer == this || pPlayer->has_disconnected || pPlayer->GetObserverMode() != OBS_NONE || (pPlayer->pev->effects & EF_NODRAW) || pPlayer->m_iTeam == UNASSIGNED || (bSameTeam && pPlayer->m_iTeam != m_iTeam))
+	if (!pPlayer || pPlayer == this)
 		return nullptr;
 
+	if (pPlayer->has_disconnected)
+		return nullptr;
+
+	if (pPlayer->GetObserverMode() != OBS_NONE)
+		return nullptr;
+
+	if (pPlayer->m_iTeam == UNASSIGNED || (bSameTeam && pPlayer->m_iTeam != m_iTeam))
+		return nullptr;
+
+	if (pPlayer->pev->effects & EF_NODRAW)
+	{
+#ifdef REGAMEDLL_FIXES
+		bool bStillDying = (pPlayer->pev->deadflag >= DEAD_DYING && (gpGlobals->time <= (pPlayer->m_fDeadTime + 3.0f)));
+		if (bStillDying && !(pPlayer->m_afPhysicsFlags & PFLAG_OBSERVER))
+			return pPlayer; // keep observing to victim until dying, even if it is invisible
+#endif
+
+		return nullptr;
+	}
+
 	return pPlayer;
 }