Building a tag cloud in WPF

Question

I'm trying to build a tag cloud in WPF based on an existing implementation [Download Source]. I didn't understand completely the implementation and my problem is, that instead of having the FontSize binded to the number of items in a collection, I want to bind it to some other values contained in a class. So in this part here,

FontSize="{Binding Path=ItemCount, Converter={StaticResource CountToFontSizeConverter}}"

I want to bind the FontSize to something else. How do I do that? Where does ItemCount belong to?

Thanks

Answer 1

ItemCount belongs to the group inside the collection view that is generated from that Tag.

e.g. if i have a list

A A B B B C

And i group them i get:

Group A : ItemCount = 2
Group B : ItemCount = 3
Group C : ItemCount = 1

The whole point of a Tag-Cloud is to bind to that very property because you want to visualize how often a certain tag is used.

---

To respond to your comments, the bare-bones setup should be something like this:

<ItemsControl ItemsSource="{Binding Data}">
    <ItemsControl.Resources>
        <vc:CountToFontSizeConverter x:Key="CountToFontSizeConverter"/>
    </ItemsControl.Resources>
    <ItemsControl.ItemsPanel>
        <ItemsPanelTemplate>
            <WrapPanel />
        </ItemsPanelTemplate>
    </ItemsControl.ItemsPanel>
    <ItemsControl.ItemTemplate>
        <DataTemplate>
            <TextBlock Text="{Binding Name}" Margin="2"
                       FontSize="{Binding Count, Converter={StaticResource CountToFontSizeConverter}}"/>
        </DataTemplate>
    </ItemsControl.ItemTemplate>
</ItemsControl>

I assume that your data-object class exposes the properties Name and Count, to make sure that the size changes as count goes up that data-object class needs to implement INotifyPropertyChanged, that is about all there is to it.

public class Tag : INotifyPropertyChanged
{
    private string _name = null;
    public string Name
    {
        get { return _name; }
        set
        {
            if (_name != value)
            {
                _name = value;
                OnPropertyChanged("Name");
            }
        }
    }

    private int _count = 0;
    public int Count
    {
        get { return _count; }
        set
        {
            if (_count != value)
            {
                _count = value;
                OnPropertyChanged("Count");
            }
        }
    }

    //...

    public event PropertyChangedEventHandler PropertyChanged;

    protected virtual void OnPropertyChanged(string propertyName)
    {
        if (this.PropertyChanged != null)
        {
            this.PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
        }
    }
}

Answer 2

ItemCount is a property of whatever instance is contained in the DataContext property of the WPF object you want to change the FontSize of. In the hierarchy tree, everything from FrameworkElement onwards inherits the "DataContext" property.

With "snoop" you can look into the UI tree of a WPF App at runtime and e.g. figure out what objects live in your DataContext at any given time.