Hint at something extensible for how to set back technically.

Versions, mods, ...

NCPCore/src/main/java/fr/neatmonster/nocheatplus/checks/moving/MovingListener.java

@@ -1367,6 +1367,7 @@ private void prepareSetBack(final Player player, final PlayerMoveEvent event, fi
         aux.resetPositionsAndMediumProperties(player, newTo, data, cc); // TODO: Might move into prepareSetBack, experimental here.
 
         // Set new to-location.
+        // TODO: Perhaps need to distinguish by version+settings?
         // event.setTo(newTo); // LEGACY: pre-2017-03-24
         event.setCancelled(true);
         // NOTE: A teleport is scheduled on MONITOR priority, if still relevant.
@@ -1432,15 +1433,13 @@ public void onPlayerMoveMonitor(final PlayerMoveEvent event) {
      * @param mData
      * @param data
      */
-    private void onCancelledMove(final Player player, final Location from, final int tick, final long now, final MovingData mData, final MovingConfig mCc, final CombinedData data) {
+    private void onCancelledMove(final Player player, final Location from, final int tick, final long now, 
+            final MovingData mData, final MovingConfig mCc, final CombinedData data) {
         // Detect our own set back, choice of reference location.
         if (mData.hasSetBack()) {
             final Location ref = mData.getTeleported();
-            /*
-             * Attempt to control the immediate set back location, allowing to
-             * do without the PlayerTeleportEvent, if successful.
-             */
-            LocUtil.set(from, ref); // Hope the from location is used for teleport (fastest way).
+            // TODO: Initiate further action depending on version/capabilities (update getFrom()).
+            LocUtil.set(from, ref); // Attempt to do without a PlayerTeleportEvent as follow up.
             // Schedule the teleport, because it might be faster than the next incoming packet.
             final UUID playerId = player.getUniqueId();
             if (!TickTask.isPlayerGoingToBeSetBack(playerId)) {
@@ -1507,6 +1506,7 @@ else if (!from.getWorld().getName().equals(toWorldName)) {
             mData.updateTrace(player, to, tick, mcAccess.getHandle());
             if (mData.hasTeleported()) {
                 if (TickTask.isPlayerGoingToBeSetBack(player.getUniqueId())) {
+                    // TODO: If legacy behavior with setTo is supported, adjust to it here as well.
                     // Skip.
                     if (mData.debug) {
                         debug(player, "Event not cancelled, despite a set back has been scheduled. Ignore set back.");

NCPCore/src/main/java/fr/neatmonster/nocheatplus/checks/moving/player/PlayerSetBackMethod.java

@@ -0,0 +1,76 @@
+package fr.neatmonster.nocheatplus.checks.moving.player;
+
+/**
+ * Provide something to be able to tell how to set back players technically.
+ * 
+ * @author asofold
+ *
+ */
+public class PlayerSetBackMethod {
+
+    // TODO: Might use more speaking method names (cancelPlayerMoveEvent)
+
+
+    // FLAGS (Type might change to long, if so much distinction is necessary).
+
+    /** PlayerMoveEvent.setTo is used (legacy). */
+    private static final int SET_TO = 0x01;
+    /** PlayerMoveEvent.setCancelled(true) is used. */
+    private static final int CANCEL = 0x02;
+    /** PlayerMoveEvent.getFrom() is updated with the set back location. */
+    private static final int UPDATE_FROM = 0x04;
+    /** An additional teleport is scheduled for safety. */
+    private static final int SCHEDULE = 0x08;
+
+
+    // DEFAULTS
+
+    public static final PlayerSetBackMethod LEGACY = new PlayerSetBackMethod(SET_TO);
+    public static final PlayerSetBackMethod CAUTIOUS = new PlayerSetBackMethod(CANCEL | UPDATE_FROM | SCHEDULE);
+    public static final PlayerSetBackMethod MODERN = new PlayerSetBackMethod(CANCEL | UPDATE_FROM);
+
+    public static final PlayerSetBackMethod fromString(String input) {
+        // TODO: Perhpas complain for incomplete/wrong content, much later.
+        input = input.toLowerCase().replaceAll("_", "");
+        int flags = 0;
+        if (input.contains("setto")) {
+            flags |= SET_TO;
+        }
+        if (input.contains("cancel")) {
+            flags |= CANCEL;
+        }
+        if (input.contains("updatefrom")) {
+            flags |= UPDATE_FROM;
+        }
+        if (input.contains("schedule")) {
+            flags |= SCHEDULE;
+        }
+        return new PlayerSetBackMethod(flags);
+    }
+
+
+    // INSTANCE
+
+    private final int flags;
+
+    public PlayerSetBackMethod(int flags) {
+        this.flags = flags;
+    }
+
+    public boolean shouldSetTo() {
+        return (flags & SET_TO) != 0;
+    }
+
+    public boolean shouldCancel() {
+        return (flags & CANCEL) != 0;
+    }
+
+    public boolean shouldUpdateFrom() {
+        return (flags & UPDATE_FROM) != 0;
+    }
+
+    public boolean shouldSchedule() {
+        return (flags & SCHEDULE) != 0;
+    }
+
+}