Add draggable container regression tests (#4201)

Author: shai-almog

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

@@ -0,0 +1,89 @@
+package com.codename1.ui;
+
+import com.codename1.components.SpanButton;
+import com.codename1.junit.FormTest;
+import com.codename1.junit.UITestBase;
+import com.codename1.ui.geom.Dimension;
+import com.codename1.ui.layouts.BorderLayout;
+import com.codename1.ui.layouts.BoxLayout;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+class DraggableLeadComponentTest extends UITestBase {
+
+    private static final int DRAG_DELTA = 25;
+
+    @FormTest
+    void draggableContainerStartsDragWithoutLead() {
+        implementation.setBuiltinSoundsEnabled(false);
+        Form form = Display.getInstance().getCurrent();
+        form.setLayout(new BoxLayout(BoxLayout.Y_AXIS));
+
+        Button button = new Button("Normal Button, no lead");
+        button.setPreferredSize(new Dimension(200, 48));
+        Button other = new Button("Other");
+        other.setPreferredSize(new Dimension(120, 48));
+        Container draggableContainer = BorderLayout.centerCenterEastWest(button, other, null);
+        draggableContainer.setDraggable(true);
+        form.add(draggableContainer);
+        form.revalidate();
+
+        Component draggedComponent = performPressDragAndReadDragged(form, button);
+        assertEquals(draggableContainer, draggedComponent, "Draggable containers should start dragging even without a lead component");
+    }
+
+    @FormTest
+    void draggableContainerWithLeadButtonStartsDrag() {
+        implementation.setBuiltinSoundsEnabled(false);
+        Form form = Display.getInstance().getCurrent();
+        form.setLayout(new BoxLayout(BoxLayout.Y_AXIS));
+
+        Button button = new Button("Normal Button, lead");
+        button.setPreferredSize(new Dimension(200, 48));
+        Button other = new Button("Other");
+        other.setPreferredSize(new Dimension(120, 48));
+        Container draggableContainer = BorderLayout.centerCenterEastWest(button, other, null);
+        draggableContainer.setDraggable(true);
+        draggableContainer.setLeadComponent(button);
+        form.add(draggableContainer);
+        form.revalidate();
+
+        Component draggedComponent = performPressDragAndReadDragged(form, button);
+        assertEquals(draggableContainer, draggedComponent, "Lead component should initiate a drag on its container");
+    }
+
+    @FormTest
+    void draggableContainerWithSpanButtonLeadStartsDrag() {
+        implementation.setBuiltinSoundsEnabled(false);
+        Form form = Display.getInstance().getCurrent();
+        form.setLayout(new BoxLayout(BoxLayout.Y_AXIS));
+
+        SpanButton spanButton = new SpanButton("SpanButton, lead");
+        spanButton.setPreferredSize(new Dimension(200, 48));
+        Button other = new Button("Other");
+        other.setPreferredSize(new Dimension(120, 48));
+        Container draggableContainer = BorderLayout.centerCenterEastWest(spanButton, other, null);
+        draggableContainer.setDraggable(true);
+        draggableContainer.setLeadComponent(other);
+        form.add(draggableContainer);
+        form.revalidate();
+
+        Component draggedComponent = performPressDragAndReadDragged(form, other);
+        assertEquals(draggableContainer, draggedComponent, "Containers with SpanButton children should still drag when a lead component is provided");
+    }
+
+    private Component performPressDragAndReadDragged(Form form, Component interactionComponent) {
+        assertTrue(interactionComponent.getWidth() > 0, "Interaction component should be laid out with a width");
+        assertTrue(interactionComponent.getHeight() > 0, "Interaction component should be laid out with a height");
+
+        int startX = interactionComponent.getAbsoluteX() + Math.max(1, interactionComponent.getWidth() / 2);
+        int startY = interactionComponent.getAbsoluteY() + Math.max(1, interactionComponent.getHeight() / 2);
+
+        implementation.dispatchPointerPress(startX, startY);
+        implementation.dispatchPointerDrag(startX + DRAG_DELTA, startY + DRAG_DELTA);
+        implementation.dispatchPointerDrag(startX + (DRAG_DELTA * 2), startY + (DRAG_DELTA * 2));
+        Component draggedComponent = form.getDraggedComponent();
+        implementation.dispatchPointerRelease(startX + (DRAG_DELTA * 2), startY + (DRAG_DELTA * 2));
+        return draggedComponent;
+    }
+}