SWT 可拖拉的CTabFolder

   原本以为CTabFolder中的元素默认支持可拖拉事件，无奈发现需要自己实现。实现如下代码：

public static void main(String[] args) {
        final Display display = new Display();
        Shell shell = new Shell(display);
        shell.setLayout(new GridLayout());
        final CTabFolder tabFolder =  new CTabFolder(shell, SWT.CLOSE | SWT.BORDER | SWT.FLAT);
        tabFolder.setSimple(false);
        tabFolder.setLayoutData(new GridData(GridData.FILL_BOTH));
        for (int i = 0; i < 5; i++) {
            CTabItem item = new CTabItem(tabFolder, SWT.NONE);
            item.setText("item " + i);
            Text text = new Text(tabFolder, SWT.BORDER | SWT.MULTI | SWT.VERTICAL);
            text.setText("Text control for " + i);
            item.setControl(text);
        }
        Listener listener = new Listener() {
            boolean drag = false;
            boolean exitDrag = false;
            CTabItem dragItem;
            Cursor cursorSizeAll = new Cursor(null, SWT.CURSOR_SIZEALL);
            Cursor cursorIbeam = new Cursor(null, SWT.CURSOR_NO);
            Cursor cursorArrow = new Cursor(null, SWT.CURSOR_ARROW);

            public void handleEvent(Event e) {
                Point p = new Point(e.x, e.y);
                if (e.type == SWT.DragDetect) {
                    p = tabFolder.toControl(display.getCursorLocation()); // see eclipse bug 43251
                }
                switch (e.type) {
                    // 拖拉Tab
                    case SWT.DragDetect: {
                        CTabItem item = tabFolder.getItem(p);
                        if (item == null) {
                            return;
                        }
                        
                        drag = true;
                        exitDrag = false;
                        dragItem = item;
                        
                        // 换鼠标形状
                        tabFolder.getShell().setCursor(cursorIbeam);
                        break;
                    }
                    // 鼠标进入区域
                    case SWT.MouseEnter:
                        if (exitDrag) {
                            exitDrag = false;
                            drag = e.button != 0;
                        }
                        break;
                    // 鼠标离开区域
                    case SWT.MouseExit:
                        if (drag) {
                            tabFolder.setInsertMark(null, false);
                            exitDrag = true;
                            drag = false;
                            
                            // 换鼠标形状
                            tabFolder.getShell().setCursor(cursorArrow);
                        }
                        break;
                    // 松开左键
                    case SWT.MouseUp: {
                        if (!drag) {
                            return;
                        }
                        tabFolder.setInsertMark(null, false);
                        CTabItem item = tabFolder.getItem(new Point(p.x, 1));
                        
                        if (item != null) {
                            int index = tabFolder.indexOf(item);
                            int newIndex = tabFolder.indexOf(item);
                            int oldIndex = tabFolder.indexOf(dragItem);
                            if (newIndex != oldIndex) {
                                boolean after = newIndex > oldIndex;
                                index = after ? index + 1 : index/* - 1*/;
                                index = Math.max(0, index);
                                
                                CTabItem newItem = new CTabItem(tabFolder, SWT.NONE, index);
                                newItem.setText(dragItem.getText());
                                
                                Control c = dragItem.getControl();
                                dragItem.setControl(null);
                                newItem.setControl(c);
                                dragItem.dispose();
                                
                                tabFolder.setSelection(newItem);
                                
                            }
                        }
                        drag = false;
                        exitDrag = false;
                        dragItem = null;
                        
                        // 换鼠标形状
                        tabFolder.getShell().setCursor(cursorArrow);
                        break;
                    }
                    // 鼠标移动
                    case SWT.MouseMove: {
                        if (!drag) {
                            return;
                        }
                        CTabItem item = tabFolder.getItem(new Point(p.x, 2));
                        if (item == null) {
                            tabFolder.setInsertMark(null, false);
                            return;
                        }
                        Rectangle rect = item.getBounds();
                        boolean after = p.x > rect.x + rect.width / 2;
                        tabFolder.setInsertMark(item, after);
                        
                        // 换鼠标形状
                        tabFolder.getShell().setCursor(cursorSizeAll);
                        break;
                    }
                }
            }
        };
        tabFolder.addListener(SWT.DragDetect, listener);
        tabFolder.addListener(SWT.MouseUp, listener);
        tabFolder.addListener(SWT.MouseMove, listener);
        tabFolder.addListener(SWT.MouseExit, listener);
        tabFolder.addListener(SWT.MouseEnter, listener);
        shell.open();
        while (!shell.isDisposed()) {
            if (!display.readAndDispatch())
                display.sleep();
        }
        display.dispose();
    }