Question

How do I write the code that flows items in a GridView (XAML-Win8) group, according to the below illustration?

I currently have a custom TemplateSelector that selects a different (larger) template for the first item, but the flow as specified here:

<GroupStyle.Panel>
    <ItemsPanelTemplate>
        <q42:WrapPanel Orientation="Horizontal" Width="440" Margin="0,0,80,0"/>
        <!-- also tried VariableSizedWrapGrid -->
    </ItemsPanelTemplate>
</GroupStyle.Panel>

Wraps items 1 through 3 similarly, but then places item 4 at item 6’s position, without filling out items 4 nor 5.

Question becomes; how do I write code that acts similar to css:

.item  { display: inline-block; }
.item1 { float: left; }

, which would make the items flow like I want?

Answer 1

Andreas Hammar linked me to a working solution:

using System.Collections.Generic;
using Application1.Data;
using Windows.Foundation;
using Windows.UI.Xaml;
using Windows.UI.Xaml.Controls;

namespace Application1
{
    public class MyGridView : GridView
    {
        int _rowVal;
        int _colVal;
        readonly List<Size> _sequence;

        public MyGridView()
        {
            _sequence = new List<Size>
                {
                    LayoutSizes.PrimaryItem,
                    LayoutSizes.SecondarySmallItem,
                    LayoutSizes.SecondarySmallItem,
                    LayoutSizes.OtherSmallItem,
                    LayoutSizes.OtherSmallItem, // 5 
                    LayoutSizes.OtherSmallItem,
                    LayoutSizes.SecondaryTallItem, // 7
                    LayoutSizes.OtherSmallItem,
                    LayoutSizes.SecondarySmallItem, // 9
                    LayoutSizes.OtherSmallItem,
                    LayoutSizes.SecondarySmallItem, // 11
                    LayoutSizes.SecondarySmallItem,
                    LayoutSizes.OtherSmallItem,
                    LayoutSizes.OtherSmallItem
                };
        }

        protected override void PrepareContainerForItemOverride(DependencyObject element, object item)
        {
            base.PrepareContainerForItemOverride(element, item);
            var dataItem = item as SampleDataItem;
            var index = -1;

            if (dataItem != null)
            {
                index = dataItem.Group.Items.IndexOf(dataItem);
            }

            if (index >= 0 && index < _sequence.Count)
            {
                _colVal = (int) _sequence[index].Width;
                _rowVal = (int) _sequence[index].Height;
            }
            else
            {
                _colVal = (int) LayoutSizes.OtherSmallItem.Width;
                _rowVal = (int) LayoutSizes.OtherSmallItem.Height;
            }

            VariableSizedWrapGrid.SetRowSpan(element as UIElement, _rowVal);
            VariableSizedWrapGrid.SetColumnSpan(element as UIElement, _colVal);
        }
    }

    public static class LayoutSizes
    {
        public static Size PrimaryItem = new Size(6, 2);
        public static Size SecondarySmallItem = new Size(3, 1);
        public static Size SecondaryTallItem = new Size(2, 2);
        public static Size OtherSmallItem = new Size(2, 1);
    }
}

    <local:MyGridView.ItemsPanel>
        <ItemsPanelTemplate>                        
            <VirtualizingStackPanel Orientation="Horizontal"/>
        </ItemsPanelTemplate>
    </local:MyGridView.ItemsPanel>
    <local:MyGridView.GroupStyle>
        <GroupStyle>
            <GroupStyle.HeaderTemplate>
                <DataTemplate>
                    <Grid Margin="1,0,0,6">
                        <Button
                            AutomationProperties.Name="Group Title"
                            Content="{Binding Title}"
                            Click="Header_Click"
                            Style="{StaticResource TextButtonStyle}"/>
                    </Grid>
                </DataTemplate>
            </GroupStyle.HeaderTemplate>
            <GroupStyle.Panel>
                <ItemsPanelTemplate>
                    <VariableSizedWrapGrid ItemWidth="80" ItemHeight="160" Orientation="Vertical" Margin="0,0,80,0" MaximumRowsOrColumns="3"/>
                </ItemsPanelTemplate>
            </GroupStyle.Panel>
        </GroupStyle>
    </local:MyGridView.GroupStyle>
</local:MyGridView>