Add draggable tabs unit test (#4203)

Author: shai-almog

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

@@ -0,0 +1,96 @@
+package com.codename1.ui;
+
+import com.codename1.junit.FormTest;
+import com.codename1.junit.UITestBase;
+import com.codename1.testing.TestCodenameOneImplementation;
+import com.codename1.ui.layouts.BorderLayout;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertSame;
+
+class DraggableTabsTest extends UITestBase {
+
+    @FormTest
+    void draggingTabHeaderReordersTabs() {
+        implementation.setBuiltinSoundsEnabled(false);
+        Form form = Display.getInstance().getCurrent();
+        form.removeAll();
+        form.setLayout(new BorderLayout());
+
+        Tabs tabs = new Tabs();
+        Label tabOne = new Label("Tab 1");
+        Label tabTwo = new Label("Tab 2");
+        Label tabThree = new Label("Tab 3");
+        Label tabFour = new Label("Tab 4");
+        tabs.addTab("T1", tabOne);
+        tabs.addTab("T2", tabTwo);
+        tabs.addTab("T3", tabThree);
+        tabs.addTab("T4", tabFour);
+
+        enableTabDragging(tabs);
+
+        form.add(BorderLayout.CENTER, tabs);
+        form.revalidate();
+
+        Container headers = tabs.getTabsContainer();
+        Component firstHeader = headers.getComponentAt(0);
+        Component thirdHeader = headers.getComponentAt(2);
+
+        int startX = firstHeader.getAbsoluteX() + firstHeader.getWidth() / 2;
+        int startY = firstHeader.getAbsoluteY() + firstHeader.getHeight() / 2;
+        int dragX = startX + 10;
+        int dragY = startY + 5;
+        int targetX = thirdHeader.getAbsoluteX() + thirdHeader.getWidth() / 2;
+        int targetY = thirdHeader.getAbsoluteY() + thirdHeader.getHeight() / 2;
+
+        TestCodenameOneImplementation impl = implementation;
+        impl.dispatchPointerPress(startX, startY);
+        impl.dispatchPointerDrag(dragX, dragY);
+        impl.dispatchPointerDrag(targetX, targetY);
+        impl.dispatchPointerRelease(targetX, targetY);
+
+        assertEquals(4, tabs.getTabCount());
+        assertEquals("T2", tabs.getTabTitle(0));
+        assertEquals("T1", tabs.getTabTitle(1));
+        assertEquals("T3", tabs.getTabTitle(2));
+        assertEquals("T4", tabs.getTabTitle(3));
+        assertSame(tabTwo, tabs.getTabComponentAt(0));
+        assertSame(tabOne, tabs.getTabComponentAt(1));
+        assertSame(tabThree, tabs.getTabComponentAt(2));
+        assertSame(tabFour, tabs.getTabComponentAt(3));
+    }
+
+    private void enableTabDragging(final Tabs tabs) {
+        final Container tabsContainer = tabs.getTabsContainer();
+        tabsContainer.setDropTarget(true);
+        for (final Component header : tabsContainer) {
+            header.setDraggable(true);
+            header.addDropListener(e -> {
+                e.consume();
+                int x = e.getX();
+                int y = e.getY();
+                int sourceIndex = tabsContainer.getComponentIndex(header);
+                if (sourceIndex < 0) {
+                    return;
+                }
+                Component destination = tabsContainer.getComponentAt(x, y);
+                if (destination == header) {
+                    return;
+                }
+                int destIndex = tabsContainer.getComponentIndex(destination);
+                if (destIndex < 0 || destIndex == sourceIndex) {
+                    return;
+                }
+                String title = tabs.getTabTitle(sourceIndex);
+                Component content = tabs.getTabComponentAt(sourceIndex);
+                tabs.removeTabAt(sourceIndex);
+                if (destIndex > sourceIndex) {
+                    tabs.insertTab(title, null, content, destIndex - 1);
+                } else {
+                    tabs.insertTab(title, null, content, destIndex);
+                }
+                tabsContainer.animateLayout(0);
+            });
+        }
+    }
+}