TextBlock AutoTooltip

这里实现了一个简单的TextBlock的AutoTooltip，Code as Follow:

public sealed class SimpleTextBlockTrimming
    {
        public static bool GetAutoTooltip( DependencyObject obj)
        {
            return ( bool)obj.GetValue(AutoTooltipProperty);
        }
        
        public static void SetAutoTooltip( DependencyObject obj, bool value)
        {
            obj.SetValue(AutoTooltipProperty, value);
        }

        public static readonly DependencyProperty AutoTooltipProperty =
            DependencyProperty.RegisterAttached(
                "AutoTooltip",
                typeof( bool),
                typeof( SimpleTextBlockTrimming),
                new PropertyMetadata(false , OnAutoTooltipPropertyChanged));

        private static void OnAutoTooltipPropertyChanged( DependencyObject d, DependencyPropertyChangedEventArgs e)
        {
            var textBlock = d as TextBlock;
            if (textBlock == null)
            {
                return;
            }

            if (e.NewValue.Equals( true))
            {
                textBlock.TextTrimming = TextTrimming.CharacterEllipsis;
                textBlock.MouseEnter += textBlock_MouseEnter;
            }
            else
            {
                textBlock.MouseEnter -= textBlock_MouseEnter;
            }
        }

        private static void textBlock_MouseEnter( object sender, MouseEventArgs e)
        {
            var tblock = sender as TextBlock;
            if ( null == tblock)
                return;

            ToolTipService.SetToolTip(tblock, IsTextTrimmed(tblock) ? tblock.Text : null);
        }

        private static bool IsTextTrimmed( TextBlock textBlock)
        {
            Typeface typeface = new Typeface(textBlock.FontFamily,
                textBlock.FontStyle,
                textBlock.FontWeight,
                textBlock.FontStretch);

            // FormattedText is used to measure the whole width of the text held up by TextBlock container.
            FormattedText formattedText = new FormattedText (
                textBlock.Text,
                System.Threading. Thread.CurrentThread.CurrentCulture,
                textBlock.FlowDirection,
                typeface,
                textBlock.FontSize,
                textBlock.Foreground);

            return formattedText.Width - textBlock.ActualWidth > 2;
        }

    }