Add low-level hook for SDL3 input events (#2867)

* Add low-level hook for SDL3 input events. Resolves #2864

* Apply code review suggestion

Author: Ivan1pl

jme3-lwjgl3/src/main/java/com/jme3/input/lwjgl/SdlEventListener.java

@@ -0,0 +1,51 @@
+/*
+ * Copyright (c) 2009-2026 jMonkeyEngine
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ * * Redistributions of source code must retain the above copyright
+ *   notice, this list of conditions and the following disclaimer.
+ *
+ * * Redistributions in binary form must reproduce the above copyright
+ *   notice, this list of conditions and the following disclaimer in the
+ *   documentation and/or other materials provided with the distribution.
+ *
+ * * Neither the name of 'jMonkeyEngine' nor the names of its contributors
+ *   may be used to endorse or promote products derived from this software
+ *   without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
+ * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
+ * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+ * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
+ * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
+ * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
+ * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+ * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+package com.jme3.input.lwjgl;
+
+import com.jme3.system.lwjgl.LwjglWindow;
+import org.lwjgl.sdl.SDL_Event;
+
+/**
+ * Listen to raw SDL events.
+ *
+ * @author Ivan1pl
+ */
+public interface SdlEventListener {
+
+    /**
+     * When registered by {@link LwjglWindow#registerSdlEventListener(SdlEventListener)},
+     * it gets invoked on each polled SDL event before it is passed to jME inputs.
+     *
+     * @param event SDL event to handle
+     */
+    void onSDLEvent(SDL_Event event);
+}

jme3-lwjgl3/src/main/java/com/jme3/input/lwjgl/SdlJoystickInput.java

@@ -28,7 +28,7 @@
  *
  * @author Riccardo Balbo
  */
-public class SdlJoystickInput implements JoyInput {
+public class SdlJoystickInput implements JoyInput, SdlEventListener {
 
     private static final Logger LOGGER = Logger.getLogger(SdlJoystickInput.class.getName());
     private final AppSettings settings;
@@ -290,6 +290,7 @@ public boolean onPointerUp(int pointerId, float x, float y, long time) {
         return joystick != null && joystick.onPointerUp(pointerId, x, y, time);
     }
 
+    @Override
     public void onSDLEvent(SDL_Event evt) {
         int type = evt.type();
         if (!(listener instanceof InputManager)) {

jme3-lwjgl3/src/main/java/com/jme3/input/lwjgl/SdlKeyInput.java

@@ -49,7 +49,7 @@
 /**
  * SDL implementation of {@link KeyInput}.
  */
-public class SdlKeyInput implements KeyInput {
+public class SdlKeyInput implements KeyInput, SdlEventListener {
 
     private static final Logger LOGGER = Logger.getLogger(SdlKeyInput.class.getName());
 
@@ -80,6 +80,7 @@ public void resetContext() {
 
     }
 
+    @Override
     public void onSDLEvent(SDL_Event event) {
         final int type = event.type();
         if (type == SDL_EVENT_KEY_DOWN || type == SDL_EVENT_KEY_UP) {

jme3-lwjgl3/src/main/java/com/jme3/input/lwjgl/SdlMouseInput.java

@@ -65,7 +65,7 @@
 /**
  * SDL implementation of {@link MouseInput}.
  */
-public class SdlMouseInput implements MouseInput {
+public class SdlMouseInput implements MouseInput, SdlEventListener {
 
     private static final Logger LOGGER = Logger.getLogger(SdlMouseInput.class.getName());
     private static final int WHEEL_SCALE = 120;
@@ -127,6 +127,7 @@ public void resetContext() {
         setCursorVisible(cursorVisible);
     }
 
+    @Override
     public void onSDLEvent(SDL_Event event) {
         final int type = event.type();
 

jme3-lwjgl3/src/main/java/com/jme3/system/lwjgl/LwjglWindow.java

@@ -37,6 +37,7 @@
 import com.jme3.input.KeyInput;
 import com.jme3.input.MouseInput;
 import com.jme3.input.TouchInput;
+import com.jme3.input.lwjgl.SdlEventListener;
 import com.jme3.input.lwjgl.SdlJoystickInput;
 import com.jme3.input.lwjgl.SdlKeyInput;
 import com.jme3.input.lwjgl.SdlMouseInput;
@@ -204,6 +205,7 @@ public abstract class LwjglWindow extends LwjglContext implements Runnable {
 
     private final JmeContext.Type type;
     private final SafeArrayList<WindowSizeListener> windowSizeListeners = new SafeArrayList<>(WindowSizeListener.class);
+    private final SafeArrayList<SdlEventListener> sdlEventListeners = new SafeArrayList<>(SdlEventListener.class);
     private final AtomicBoolean windowCloseRequested = new AtomicBoolean(false);
 
     private Thread mainThread;
@@ -255,6 +257,14 @@ public void removeWindowSizeListener(WindowSizeListener listener) {
         windowSizeListeners.remove(listener);
     }
 
+    public void registerSdlEventListener(SdlEventListener listener) {
+        sdlEventListeners.add(listener);
+    }
+
+    public void removeSdlEventListener(SdlEventListener listener) {
+        sdlEventListeners.remove(listener);
+    }
+
     private static void disableNvidiaThreadedOptimizations() {
         if (SDL_setenv_unsafe("__GL_THREADED_OPTIMIZATIONS", "0", 1) != 0) {
             throw new IllegalStateException("Unable to disable NVIDIA OpenGL threaded optimizations: "
@@ -1111,14 +1121,21 @@ private void handleWindowEvent(SDL_Event event) {
     }
 
     private void dispatchSDLEvent(SDL_Event event) {
-        if (keyInput instanceof SdlKeyInput) {
-            ((SdlKeyInput) keyInput).onSDLEvent(event);
+        for (SdlEventListener listener : sdlEventListeners.getArray()) {
+            try {
+                listener.onSDLEvent(event);
+            } catch (Exception e) {
+                LOGGER.log(Level.SEVERE, "Error handling SDL event", e);
+            }
+        }
+        if (keyInput instanceof SdlEventListener) {
+            ((SdlEventListener) keyInput).onSDLEvent(event);
         }
-        if (mouseInput instanceof SdlMouseInput) {
-            ((SdlMouseInput) mouseInput).onSDLEvent(event);
+        if (mouseInput instanceof SdlEventListener) {
+            ((SdlEventListener) mouseInput).onSDLEvent(event);
         }
-        if (joyInput instanceof SdlJoystickInput) {
-            ((SdlJoystickInput) joyInput).onSDLEvent(event);
+        if (joyInput instanceof SdlEventListener) {
+            ((SdlEventListener) joyInput).onSDLEvent(event);
         }
     }