Add regression test for draggable lead component drag finished (#4198)

Author: shai-almog

maven/core-unittests/src/test/java/com/codename1/ui/DnDRegression3048Test.java

@@ -0,0 +1,64 @@
+package com.codename1.ui;
+
+import com.codename1.junit.FormTest;
+import com.codename1.junit.UITestBase;
+import com.codename1.ui.Container;
+import com.codename1.ui.Display;
+import com.codename1.ui.Form;
+import com.codename1.ui.Label;
+import com.codename1.ui.geom.Dimension;
+import com.codename1.ui.layouts.BoxLayout;
+
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+/**
+ * Regression test for drag and drop interactions when a container sets a lead component
+ * that is also draggable. This mimics the behaviour from the DnDRegression3048 sample and
+ * ensures drag events propagate through the full stack using {@link Form#pointerPressed(int, int)}
+ * and related APIs.
+ */
+class DnDRegression3048Test extends UITestBase {
+
+    @FormTest
+    void dragFinishedFiresWhenDraggingLeadComponent() {
+        implementation.setBuiltinSoundsEnabled(false);
+        Form form = Display.getInstance().getCurrent();
+
+        Container container = new Container(BoxLayout.y());
+        Label imageLabel = new Label("icon");
+        imageLabel.setPreferredSize(new Dimension(48, 48));
+        imageLabel.setDraggable(true);
+
+        container.putClientProperty("isTest", Boolean.TRUE);
+        container.setLeadComponent(imageLabel);
+        container.setDraggable(true);
+
+        container.add(imageLabel);
+        container.add(new Label("Another label in the container"));
+        form.add(container);
+        form.revalidate();
+
+        final int[] pointerDraggedCount = {0};
+        final int[] dragFinishedCount = {0};
+        final int[] leadDragFinishedCount = {0};
+
+        imageLabel.addPointerDraggedListener(evt -> pointerDraggedCount[0]++);
+        container.addDragFinishedListener(evt -> dragFinishedCount[0]++);
+        imageLabel.addDragFinishedListener(evt -> leadDragFinishedCount[0]++);
+
+        int startX = imageLabel.getAbsoluteX() + 10;
+        int startY = imageLabel.getAbsoluteY() + 10;
+        int endX = startX + 30;
+        int endY = startY + 30;
+
+        form.pointerPressed(startX, startY);
+        form.pointerDragged(endX, endY);
+        form.pointerDragged(endX + 10, endY + 10);
+        form.pointerReleased(endX, endY);
+
+        assertTrue(pointerDraggedCount[0] > 0, "Lead component should receive drag events");
+        assertTrue(dragFinishedCount[0] > 0 || leadDragFinishedCount[0] > 0,
+                "Drag finished events should fire on the container or its lead component");
+    }
+}
+