How can I determine if my TextBlock text is being trimmed?

user_71183 0
Viewed 18076

The following textblock wraps and trims as expected. The elipsis "..." is displayed when the text is trimmed.

<TextBlock 
    MaxWidth="60" 
    MaxHeight="60" 
    Text="This is some long text which I would like to wrap."
    TextWrapping="Wrap" 
    TextTrimming="CharacterEllipsis" />

I would like to display a tooltip over the text with the full text, but only if the text is trimmed. I'm not sure how to reliably determine if the "..." is being shown or not.

How do I determine if the text is being trimmed or not?

textblock wpf
5 Answers

I haven't done a lot of WPF lately, so I'm not sure if this is what you're looking for, but check out this article: Customizing “lookful” WPF controls – Take 2. It's a bit complex, but it seems to address the same question you're asking. UPDATE: The website seems gone, but you can find the article in the archive. SEE Scott Chamberlain's ANSWER WITH THE SAMPLE CODE (thanks Scott).

user_525450

I had a small issue using Alex answer and had to change my logic a bit to clarify if the text in the text block was being trimmed. 

var formattedText = new FormattedText(
            Text, System.Threading.Thread.CurrentThread.CurrentCulture, FlowDirection, typeface, FontSize,
            Foreground, VisualTreeHelper.GetDpi( this ).PixelsPerDip ) { MaxTextWidth = ActualWidth };
        //Measure(new Size(Double.PositiveInfinity, Double.PositiveInfinity));

 return ( Math.Floor(formattedText.Height ) > ActualHeight || Math.Floor( formattedText.MinWidth ) > ActualWidth;

This works perfectly for me.

I defined a user control that was a TextBlock with ellipsis enabled. Then I defined 2 functions for OnMouseUp and OnMouseDown, so that when the user clicked on the textblock that had overflow it would display a tooltip with the full value.

This is the OnMouseDown function

private void TextBlockWithToolTipView_OnMouseDown(
        object sender,
        MouseButtonEventArgs e )
    {
        var typeface = new Typeface(
            FontFamily,
            FontStyle,
            FontWeight,
            FontStretch);

        var formattedText = new FormattedText(
            Text, System.Threading.Thread.CurrentThread.CurrentCulture, FlowDirection, typeface, FontSize,
            Foreground, VisualTreeHelper.GetDpi( this ).PixelsPerDip ) { MaxTextWidth = ActualWidth };

        if (Math.Floor(formattedText.Height) > ActualHeight || Math.Floor(formattedText.MinWidth) > ActualWidth )
        {
            if( ToolTip is ToolTip tt )

            {
                {
                    if( tt.PlacementTarget == null )
                    {
                        tt.PlacementTarget = this;
                    }

                    tt.IsOpen = true;
                    e.Handled = true;
                }
            }
        }
    }

And this was the Xaml bit

<TextBlock 
         ToolTipService.IsEnabled="True"
         MouseDown="TextBlockWithToolTipView_OnMouseDown"
         MouseLeave="TextBlockWithToolTipView_OnMouseLeave"   
         TextTrimming="CharacterEllipsis"
         TextWrapping="WrapWithOverflow">
<TextBlock.ToolTip>
        <ToolTip 
            DataContext="{Binding Path=PlacementTarget, RelativeSource={x:Static RelativeSource.Self}}">
        <TextBlock Text="{Binding Path=Text, Mode=OneWay }"
                       TextWrapping="Wrap"/>
        </ToolTip>
    </TextBlock.ToolTip>
</TextBlock>
user_123596330
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