RFE: getSelectedWidgets

[GoogleCodeExporter]

Request for Enhancement on PickupDragController to provide the list of 
selectedWidgets with a get method.

In our application each of the draggable nodes is a container for data and 
we now have a feature request that requires the application to know which 
nodes have been selected (via normal selection or ctrl-click) in the same 
drag area. We are using 2.5.6 so I took a look at the code for 2.6.5 but 
didn't see this capability. I looked into recording the selected widgets in 
my own class but onDragStart does not fire on ctrl-click. So I can only 
save a pointer to the context by stealing it off the first onDragStart 
event and taking advantage that you left selectedWidgets public.

We do not have the means to upgrade to GWT 1.7 yet so I can't move up to 
gwt-dnd 2.6.5. Would you be able to retrofit the method into 2.5.6 as well?

Original issue reported on code.google.com by bbla...@gmail.com on 3 Aug 2009 at 3:19

[GoogleCodeExporter]

Does selectedWidgets in the drag context provide the information you need? That 
is in 
fact the intended approach.

Original comment by fredsa on 3 Aug 2009 at 3:52

• Changed state: NeedsInfo

[GoogleCodeExporter]

The DragContext does indeed satisfy that condition but it's the way I have to 
get the 
context that is the issue. I have to add a DragHandler then listen for an event 
that 
is outside of my controller that instantiated the canvas to begin with. Only 
through 
the DragStartEvent can I get a pointer to the context.

So from the PickupDragController I can clearSelection and I can toggleSelection 
(if I 
already know which widget to toggle) but there is no method to get which, if 
any, 
draggable nodes are chosen by the user. Why would clearSelection be in 
AbstractDragController if everything it does can be handled by the DragContext 
object? The same can be said for toggleSelection.

So maybe where I'm headed in my argument is to supply access to the context 
object 
and move clearSelection and toggleSelection into DragContext. Example code 
would be

PickupDragController dragController = new PickupDragController();
...
dragController.getContext().clearSelection();

or in my case

List<Widget> selected = dragController.getContext().getSelectedWidgets();

Original comment by bbla...@gmail.com on 3 Aug 2009 at 5:14

[GoogleCodeExporter]

There are two goals here:
- The drag context is the place that maintain a list of selected widgets
- The drag controller determines how a user action to toggle particular widget 
selection affects already selected widgets. For example see 
ListBoxDragController#toggleSelection(Widget)

I'd prefer to the data (=what's selected) and the object (=drag context) live 
together, but the use cases seem to demand more.

I might suggest copying the PickupDragController source code and creating your 
own 
drag controller from it. Would that address your immediate needs? (I realize 
this is 
not always ideal, but I'm constantly trying to limit the amount of API surface 
area I 
provide since 'there be dragons')

Original comment by fredsa on 3 Aug 2009 at 5:31

[GoogleCodeExporter]

dragController.getContext()

That seems to be what he's asking for. There doesn't seem to be any other way 
of 
grabbing the context (or what's inside the dragController). 

Original comment by Christop...@gmail.com on 3 Aug 2009 at 7:16

[GoogleCodeExporter]

What about extending PickupDragController?

class MyPickupDragController extends PickupDragController {

  DragContext getDragContext() {
    return context;
  }

}

Original comment by fredsa on 3 Aug 2009 at 7:39

[GoogleCodeExporter]

Gotta say, not a fan of that way. I understand how your separating class 
responsibilities. I also 
follow the rule of keeping your variables private/protected. Here's what I was 
hoping for

public class Canvas extends Composite {

    private AbsolutePanel panel;
    private PickupDragController dragController;

    public Canvas() {
        panel = new AbsolutePanel();

        dragController = new PickupDragController(panel, true);
        dragController.setBehaviorMultipleSelection(true);

        Label label1 = new Label("LABEL1");
        Label label2 = new Label("LABEL2");

        panel.add(label1);
        panel.add(label2);

        dragController.makeDraggable(label1, label1);
        dragController.makeDraggable(label2, label2);

        initWidget(panel);
    }

    public List<Widget> getSelectedWidgets() {
        // lets's say a button calls this method
        // how can i get (easily) what is selected with just gwt-dnd code?

        return ?;


        // return dragController.getContext().getSelectedWidgets();
    }
}

Original comment by bbla...@gmail.com on 3 Aug 2009 at 8:42

[GoogleCodeExporter]

I'd like to provide access to the drag context, so settings to 'Accepted'.

I do think I need to tighten up access to the drag context fields, perhaps as 
part of this 
effort. I like that you wrote 'getSelectedWidgets()' rather than 
'selectedWidgets'. The 
GWT compiler will inline trivial getters and setters so this is effectively a 
noop change 
for production code.

Original comment by fredsa on 3 Aug 2009 at 8:58

• Changed state: Accepted

[GoogleCodeExporter]

Fixed in 985 by adding PickupDragController.getSelectedWidgets()

  public Iterable<Widget> getSelectedWidgets();

Original comment by fredsa on 13 Sep 2009 at 5:43

• Changed state: Fixed

[GoogleCodeExporter]

So what is the difference between calling context.selectedWidgets vs 
context.getSelectedWidgets(); when the later calls the former?

Regards,

SigmaSquared

Original comment by SigmaBl...@gmail.com on 23 Apr 2012 at 3:07