GXT: Filter Grid add select all columns checkbox

Question

I have a Filter Grid component similar to the icon below. What I want is to add a Select All functionality in the columns section of the header. I've done my research but I can't find any kind of solution. Not even a direction. I want to be able to attach a handler to that checkbox that will check/uncheck all of the below options.

The module in question

I'm using Sencha GXT 3.1.0 and and GWT 2.6.1

The icon

Answer 1

Here's how to do this , override createContextMenu of the GridView

ColumnModel<HashMap> cm = new ColumnModel<HashMap>(l);

GridView<HashMap> gridView = new GridView<HashMap>()
{
    @Override
    protected void initHeader()
    {
        super.initHeader();
    }

    protected Menu createContextMenu(final int colIndex)
    {
        Menu createContextMenu = super.createContextMenu(colIndex);

        final CheckMenuItem check = new CheckMenuItem();
        check.setHideOnClick(false);
        check.setHTML("Toggle Selection");
        check.setChecked(true);

        check.addCheckChangeHandler(new CheckChangeHandler<CheckMenuItem>()
        {

            @Override
            public void onCheckChange(CheckChangeEvent<CheckMenuItem> event)
            {
                Window.alert("Toggle Selection");
            }
        });

        createContextMenu.add(check);

        return createContextMenu;

    }

};

Grid grid = new Grid(store, cm, gridView);