private void startResizing(final boolean vertical) {
        final Element glassElem = getGlass();

        isResizing = true;
        // onSplitterResizeStarted(x, y);

        // Resize glassElem to take up the entire scrollable window area
        final int height = RootPanel.getBodyElement().getScrollHeight() - 1;
        final int width = RootPanel.getBodyElement().getScrollWidth() - 1;
        glassElem.getStyle().setWidth(width, Unit.PX);
        glassElem.getStyle().setHeight(height, Unit.PX);

        if (vertical) {
            glassElem.getStyle().setCursor(Cursor.ROW_RESIZE);
        } else {
            glassElem.getStyle().setCursor(Cursor.COL_RESIZE);
        }

        RootPanel.getBodyElement().appendChild(glassElem);
    }
Sets the minimum allowable size for the given widget.
<p>
<p>
Its associated splitter cannot be dragged to a position that would make
it smaller than this size. This method has no effect for the
{@link DockLayoutPanel.Direction#CENTER} widget.
</p>

@param child   the child whose minimum size will be set
@param minSize the minimum size for this widget
stroom-core-client-widget/src/main/java/com/google/gwt/user/client/ui/MySplitLayoutPanel.java