Implement SDL focus-aware mouse delta handling

Author: Copilot

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

@@ -92,6 +92,7 @@ public class SdlMouseInput implements MouseInput {
     private float windowCoordHeight = 1f;
 
     private boolean cursorVisible = true;
+    private boolean windowFocused = true;
     private boolean x11WarpGrabMode;
     private boolean ignoreNextX11WarpEvent;
     private boolean initialized;
@@ -131,15 +132,20 @@ public void onSDLEvent(SDL_Event event) {
 
         if (type == SDL_EVENT_WINDOW_FOCUS_GAINED) {
             if (event.window().windowID() == context.getWindowId()) {
+                windowFocused = true;
+                refreshWindowMetrics();
+                initCurrentMousePosition();
                 setCursorVisible(cursorVisible);
             }
             return;
         }
 
         if (type == SDL_EVENT_WINDOW_FOCUS_LOST) {
             if (event.window().windowID() == context.getWindowId()) {
+                windowFocused = false;
                 x11WarpGrabMode = false;
                 ignoreNextX11WarpEvent = false;
+                mouseMotionEvents.clear();
                 SDL_CaptureMouse(false);
                 SDL_SetWindowMouseGrab(context.getWindowHandle(), false);
                 SDL_SetWindowRelativeMouseMode(context.getWindowHandle(), false);
@@ -154,6 +160,9 @@ public void onSDLEvent(SDL_Event event) {
             if (event.motion().windowID() != context.getWindowId()) {
                 return;
             }
+            if (!windowFocused) {
+                return;
+            }
             refreshWindowMetrics();
             final boolean relativeMode = SDL_GetWindowRelativeMouseMode(context.getWindowHandle());
             final int x;

jme3-lwjgl3/src/test/java/com/jme3/input/lwjgl/SdlMouseInputTest.java

@@ -0,0 +1,50 @@
+package com.jme3.input.lwjgl;
+
+import com.jme3.system.lwjgl.LwjglWindow;
+import java.lang.reflect.Field;
+import java.util.Queue;
+import org.junit.jupiter.api.Test;
+import org.lwjgl.sdl.SDL_Event;
+
+import static org.junit.jupiter.api.Assertions.assertTrue;
+import static org.lwjgl.sdl.SDLEvents.SDL_EVENT_MOUSE_MOTION;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.when;
+
+public class SdlMouseInputTest {
+
+    @Test
+    public void shouldIgnoreMouseMotionWhenWindowIsUnfocused() throws Exception {
+        LwjglWindow context = mock(LwjglWindow.class);
+        when(context.getWindowId()).thenReturn(7);
+
+        SdlMouseInput mouseInput = new SdlMouseInput(context);
+        setField(mouseInput, "windowFocused", false);
+
+        SDL_Event event = SDL_Event.calloc();
+        try {
+            event.type(SDL_EVENT_MOUSE_MOTION);
+            event.motion().windowID(7);
+
+            mouseInput.onSDLEvent(event);
+        } finally {
+            event.free();
+        }
+
+        Queue<?> mouseMotionEvents = getField(mouseInput, "mouseMotionEvents");
+        assertTrue(mouseMotionEvents.isEmpty());
+    }
+
+    private static void setField(Object target, String fieldName, Object value) throws Exception {
+        Field field = target.getClass().getDeclaredField(fieldName);
+        field.setAccessible(true);
+        field.set(target, value);
+    }
+
+    @SuppressWarnings("unchecked")
+    private static <T> T getField(Object target, String fieldName) throws Exception {
+        Field field = target.getClass().getDeclaredField(fieldName);
+        field.setAccessible(true);
+        return (T) field.get(target);
+    }
+}