newDragProxy

[MD]

Hi,

I want to clarify the way to override newDragProxy.

Here's my case. I need a palette whose each item is dragged on a
canvas, moved around, and resized. It is just a plain tool palette of
Label, TextBox, TextArea, and so on.

I made it with PaletteWidget and WindowPanel in examples, and which
works perfect. But some are not clear to me.

Here's the code:

@Override
protected Widget newDragProxy(DragContext context) {
AbsolutePanel container = new AbsolutePanel(); // 1

Widget proxy = null;
Widget widget = context.draggable;
widget.removeStyleName("dragdrop-dragging"); // 2

if(!(widget instanceof PaletteWidget)){
throw new IllegalStateException("Unhandled Widget class " +
widget.getClass().getName());
}

widget = ((PaletteWidget) widget).getWidget();

// Create proxy object(e.g. TextBox)
proxy = new WindowPanel(this.windowController, new HTML(), textBox,
false);
proxy.addStyleName("dragdrop-dragging"); // 2
container.add(proxy); // 1

// to make proxy work
context.draggable = proxy; // 3
context.selectedWidgets.clear(); // 4
context.selectedWidgets.add(proxy); // 4

return container; // 1
}

Some look required like 1 above by referencing to
PickupDragController#dragStart and #dragEnd.
But what about 2, 3, and 4? It doesn't work correctly without.

Without 2, a dragged palette object becomes transparent while a
dragged WindowPanel object stays opaque.
Without 3, a dragged WindowPanel object will not correctly placed.
Without 4, a dragged WindowPanel object disappears after dragEnds.

So could you clarify if I override correctly and do something wrong?
Or it is very helpful if its contract, the way to override, is clearly
stated.

Thanks!