Fix elytra emulation not working on 1.9.0 servers

src/main/java/com/viaversion/viarewind/legacysupport/feature/ElytraVelocityEmulator.java

@@ -18,6 +18,9 @@
 
 package com.viaversion.viarewind.legacysupport.feature;
 
+import com.viaversion.viarewind.legacysupport.BukkitPlugin;
+import com.viaversion.viarewind.legacysupport.util.NMSUtil;
+import com.viaversion.viarewind.legacysupport.util.ReflectionUtil;
 import com.viaversion.viaversion.api.Via;
 import com.viaversion.viaversion.api.protocol.version.ProtocolVersion;
 import org.bukkit.entity.Player;
@@ -27,9 +30,27 @@ import org.bukkit.event.Listener;
 import org.bukkit.event.player.PlayerMoveEvent;
 import org.bukkit.util.Vector;
 
+import java.lang.reflect.Method;
+import java.util.logging.Level;
+
 @SuppressWarnings("unchecked")
 public class ElytraVelocityEmulator implements Listener {
 
+    private boolean isGliding(final ProtocolVersion version, final Player player) {
+        if (version.olderThanOrEqualTo(ProtocolVersion.v1_9_1)) {
+            final Object nmsPlayer = NMSUtil.getNMSPlayer(player);
+            if (nmsPlayer == null) return false;
+
+            try {
+                final Method getFlag = ReflectionUtil.getMethod(nmsPlayer.getClass(), "getFlag", int.class);
+                return (boolean) getFlag.invoke(nmsPlayer, 7);
+            } catch (Exception e) {
+                BukkitPlugin.getInstance().getLogger().log(Level.SEVERE, "Failed to get player flag", e);
+            }
+        }
+        return player.isGliding();
+    }
+
     @EventHandler(priority = EventPriority.MONITOR, ignoreCancelled = true)
     public void onPlayerMove(PlayerMoveEvent e) {
         final Player player = e.getPlayer();
@@ -37,7 +58,10 @@ public class ElytraVelocityEmulator implements Listener {
         if (Via.getAPI().getPlayerProtocolVersion(player).newerThanOrEqualTo(ProtocolVersion.v1_9)) {
             return; // Only apply for 1.8 and below players
         }
-        if (!player.isGliding()) return; // Only apply if the player is gliding
+        final ProtocolVersion serverVersion = BukkitPlugin.getInstance().getServerProtocol();
+        if (!isGliding(serverVersion, player)) {
+            return; // Only apply if the player is gliding
+        }
 
         final Vector direction = player.getLocation().getDirection();
         final Vector velocity = player.getVelocity();

src/main/java/com/viaversion/viarewind/legacysupport/util/NMSUtil.java

@@ -86,12 +86,18 @@ public class NMSUtil {
         }
     }
 
-    public static void sendPacket(final Player player, final Object packet) {
+    public static Object getNMSPlayer(final Player player) {
-        Object nmsPlayer;
         try {
-            nmsPlayer = player.getClass().getMethod("getHandle").invoke(player);
+            return player.getClass().getMethod("getHandle").invoke(player);
         } catch (InvocationTargetException | IllegalAccessException | NoSuchMethodException e) {
             BukkitPlugin.getInstance().getLogger().log(Level.SEVERE, "Failed to get EntityPlayer from player", e);
+            return null;
+        }
+    }
+
+    public static void sendPacket(final Player player, final Object packet) {
+        final Object nmsPlayer = getNMSPlayer(player);
+        if (nmsPlayer == null) {
             return;
         }
 

src/main/java/com/viaversion/viarewind/legacysupport/util/ReflectionUtil.java

@@ -65,7 +65,9 @@ public class ReflectionUtil {
             return clazz.getDeclaredMethod(methodName, parameterTypes);
         } catch (NoSuchMethodException ex) {
             final Class<?> superClass = clazz.getSuperclass();
-            if (superClass == null) return null;
+            if (superClass == null) {
+                return null;
+            }
             return getMethod(superClass, methodName, parameterTypes);
         }
     }