    /**
     * @private
     *
     * This class is used only by the grid's HeaderContainer docked child.
     *
     * It adds the ability to shrink the vertical size of the inner container element back if a grouped
     * column header has all its child columns dragged out, and the whole HeaderContainer needs to shrink back down.
     *
     * Also, after every layout, after all headers have attained their 'stretchmax' height, it goes through and calls
     * `setPadding` on the columns so that they lay out correctly.
     */
    Ext.define('Ext.grid.ColumnLayout', {
        extend: 'Ext.layout.container.HBox',
        alias: 'layout.gridcolumn',
        type : 'gridcolumn',

        reserveOffset: false,

        firstHeaderCls: Ext.baseCSSPrefix + 'column-header-first',
        lastHeaderCls: Ext.baseCSSPrefix + 'column-header-last',

        // Collect the height of the table of data upon layout begin
        beginLayout: function (ownerContext) {
            var me = this,
                owner = me.owner,
                grid = owner.up('[scrollerOwner]'),
                view = grid.view,
                i = 0,
                items = me.getVisibleItems(),
                len = items.length,
                item;

            // If we are one side of a locking grid, then if we are on the "normal" side, we have to grab the normal view
            // for use in determining whether to subtract scrollbar width from available width.
            // The locked side does not have scrollbars, so it should not look at the view.
            if (grid.lockable) {
                if (me.owner.up('tablepanel') === view.normalGrid) {
                    view = view.normalGrid.getView();
                } else {
                    view = null;
                }
            }

            me.callParent(arguments);

            // Unstretch child items before the layout which stretches them.
            for (; i < len; i++) {
                item = items[i];
                item.removeCls([me.firstHeaderCls, me.lastHeaderCls]);
                item.el.setStyle({
                    height: 'auto'
                });
                item.titleEl.setStyle({
                    height: 'auto',
                    paddingTop: ''  // reset back to default padding of the style
                });
            }

            // Add special first/last classes
            if (len > 0) {
                items[0].addCls(me.firstHeaderCls);
                items[len - 1].addCls(me.lastHeaderCls);
            }

            // If the owner is the grid's HeaderContainer, and the UI displays old fashioned scrollbars and there is a rendered View with data in it,
            // collect the View context to interrogate it for overflow, and possibly invalidate it if there is overflow
            if (!me.owner.isHeader && Ext.getScrollbarSize().width && !grid.collapsed && view &&
                    view.rendered && (ownerContext.viewTable = view.el.child('table', true))) {
                ownerContext.viewContext = ownerContext.context.getCmp(view);
            }
        },

        roundFlex: function(width) {
            return Math.floor(width);
        },

        /**
         * @private
         * Local getContainerSize implementation accounts for vertical scrollbar in the view.
         */
        getContainerSize: function(ownerContext) {
            var me = this,
                result = me.callParent(arguments),
                viewContext = ownerContext.viewContext,
                viewHeight;

            // If we've collected a viewContext, we will also have the table height
            // If there's overflow, the View must be narrower to accomodate the scrollbar
            if (viewContext && !viewContext.heightModel.shrinkWrap &&
                    viewContext.target.componentLayout.ownerContext) { // if (its layout is running)
                viewHeight = viewContext.getProp('height');
                if (isNaN(viewHeight)) {
                    me.done = false;
                } else if (ownerContext.state.tableHeight > viewHeight) {
                    result.width -= Ext.getScrollbarSize().width;
                    ownerContext.state.parallelDone = false;
                    viewContext.invalidate();
                }
            }

    // TODO - flip the initial assumption to "we have a vscroll" to avoid the invalidate in most
    // cases (and the expensive ones to boot)

            return result;
        },

        calculate: function(ownerContext) {
            var me = this,
                viewContext = ownerContext.viewContext;

            // Collect the height of the data table if we need it to determine overflow
            if (viewContext && !ownerContext.state.tableHeight) {
                ownerContext.state.tableHeight = ownerContext.viewTable.offsetHeight;
            }
            me.callParent(arguments);
        },

        completeLayout: function(ownerContext) {
            var me = this,
                owner = me.owner,
                state = ownerContext.state,
                needsInvalidate = false,
                calculated = me.sizeModels.calculated,
                childItems, len, i, childContext, item;

            me.callParent(arguments);

            // If we have not been through this already, and the owning Container is configured
            // forceFit, is not a group column and and there is a valid width, then convert
            // widths to flexes, and loop back.
            if (!state.flexesCalculated && owner.forceFit && !owner.isHeader) {
                childItems = ownerContext.childItems;
                len = childItems.length;

                for (i = 0; i < len; i++) {
                    childContext = childItems[i];
                    item = childContext.target;

                    // For forceFit, just use allocated width as the flex value, and the proportions
                    // will end up the same whatever HeaderContainer width they are being forced into.
                    if (item.width) {
                        item.flex = ownerContext.childItems[i].flex = item.width;
                        delete item.width;
                        childContext.widthModel = calculated;
                        needsInvalidate = true;
                    }
                }

                // Recalculate based upon all columns now being flexed instead of sized.
                // Set flag, so that we do not do this infinitely
                if (needsInvalidate) {
                    me.cacheFlexes(ownerContext);
                    ownerContext.invalidate({
                        state: {
                            flexesCalculated: true
                        }
                    });
                }
            }
        },

        finalizeLayout: function() {
            var me = this,
                i = 0,
                items,
                len,
                itemsHeight,
                owner = me.owner,
                titleEl = owner.titleEl;

            // Set up padding in items
            items = me.getVisibleItems();
            len = items.length;
            // header container's items take up the whole height
            itemsHeight = owner.el.getViewSize().height;
            if (titleEl) {
                // if owner is a grouped column with children, we need to subtract the titleEl's height
                // to determine the remaining available height for the child items
                itemsHeight -= titleEl.getHeight();
            }
            for (; i < len; i++) {
                items[i].setPadding(itemsHeight);
            }
        },

        // FIX: when flexing we actually don't have enough space as we would
        // typically because of the scrollOffset on the GridView, must reserve this
        publishInnerCtSize: function(ownerContext) {
            var me = this,
                plan = ownerContext.state.boxPlan,
                size = plan.targetSize,
                cw = ownerContext.peek('contentWidth');

            // InnerCt MUST stretch to accommodate all columns so that left/right scrolling is enabled in the header container.
            if ((cw != null) && !me.owner.isHeader) {
                size.width = cw + Ext.getScrollbarSize().width;
            }

            return me.callParent(arguments);
        }
    });