CODEWITHSUNDEEP
wpfvisibilityismouseover
epalm
epalm

Reputation: 4423

IsMouseOver, Visibility, and Control dimensions

WPF:

<Window x:Class="WpfApplication1.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:local="clr-namespace:WpfApplication1"
        Title="MainWindow" Height="350" Width="525">

    <Window.Resources>
        <local:BooleanToVisibilityConverter x:Key="BooleanToVisibilityConverter"
                                            True="Visible"
                                            False="Collapsed" />
    </Window.Resources>

    <Canvas>
        <StackPanel Canvas.Left="100" Canvas.Top="100" Width="200" Height="100">
            <ListBox>
                <ListBoxItem>one</ListBoxItem>
                <ListBoxItem>two</ListBoxItem>
                <ListBoxItem>three</ListBoxItem>
            </ListBox>
            <StackPanel Orientation="Horizontal"
                        Visibility="{Binding
                                     RelativeSource={RelativeSource AncestorType={x:Type StackPanel}},
                                     Path=IsMouseOver,
                                     Converter={StaticResource BooleanToVisibilityConverter}}">
                <Button>one</Button>
                <Button>two</Button>
                <Button>three</Button>
            </StackPanel>
        </StackPanel>
    </Canvas>
</Window>

Code:

public abstract class BooleanConverter<T> : IValueConverter
{
    public BooleanConverter(T trueValue, T falseValue)
    {
        True = trueValue;
        False = falseValue;
    }

    public T True { get; set; }
    public T False { get; set; }

    public virtual object Convert(object value, Type targetType, object parameter, CultureInfo culture)
    {
        return value is bool && ((bool)value) ? True : False;
    }

    public virtual object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
    {
        return value is T && EqualityComparer<T>.Default.Equals((T)value, True);
    }
}

public class BooleanToVisibilityConverter : BooleanConverter<Visibility>
{
    public BooleanToVisibilityConverter()
        : base(Visibility.Visible, Visibility.Collapsed)
    { }
}

My the mouse hovers over the ListBox, the buttons are displayed as expected. If the mouse moves below the ListBox on the right side, the buttons vanish. Why is IsMouseOver false over there? Shouldn't the height of the outer StackPanel increase when the inner StackPanel's Visibility property changes from Collapsed to Visible?

Here's the project if you want to play with it: http://dl.dropbox.com/u/4220513/WpfApplication1.zip

enter image description here

Upvotes: 4

Views: 696

Answers (2)

Navid Rahmani
Navid Rahmani

Reputation: 7958

Use a background for your StackPanel like <StackPanel Background="Transparent">...

Upvotes: 1

Wallstreet Programmer
Wallstreet Programmer

Reputation: 9677

You need to set the background of the StackPanel (the outer one) to Transparent to detect mouse over. If background is null as in your sample, hit testing will fail.

Upvotes: 3

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