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Text Annotation Size



I’m using the following code to create a text annotation:

private void AddLabel(DateTime StartTime, DateTime EndTime, string label)
    TextAnnotation text = new TextAnnotation();
    text.YAxisId = "LeftAxis";
    text.HorizontalContentAlignment = System.Windows.HorizontalAlignment.Center;
    text.Text = label;
    text.CoordinateMode = AnnotationCoordinateMode.RelativeY;
    text.X1 = StartTime;
    text.X2 = EndTime;
    text.Y1 = .05;
    text.Y2 = 0;
    text.TextAlignment = TextAlignment.Center;
    text.TextStretch = Stretch.UniformToFill;
    text.Background = new SolidColorBrush(Color.FromArgb(0x80, 0x80, 0x80, 0x80));
    text.BorderBrush = new SolidColorBrush(Color.FromArgb(0xC0, 0xD0, 0xD0, 0xD0));
    text.BorderThickness = new Thickness(2);

Unfortunately the text doesn’t scale like I want it to though. The size of the text stays the same even when the chart is small, making the height greater than .05. Is there a way to make the text get smaller as the chart is shrunk so that it stays within the .05 Y boundary?

I attached 2 images to illustrate the issue.


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Hi Greg,

Hm…in this case I can suggest you changing the FontSize of annotations dynamically or modifying a Template of TextAnnotaion. Please, try using following control template:

                <ControlTemplate TargetType="s:TextAnnotation">
                    <Border x:Name="PART_TextAnnotationRoot"
                            Margin="{TemplateBinding Margin}"
                            Background="{TemplateBinding Background}"
                            BorderBrush="{TemplateBinding BorderBrush}"
                            BorderThickness="{TemplateBinding BorderThickness}"
                            CornerRadius="{TemplateBinding CornerRadius}">
                          <Viewbox Stretch="{TemplateBinding TextStretch}">
                        <TextBox x:Name="PART_InputTextArea"
                                 Margin="{TemplateBinding Padding}"
                                 VerticalAlignment="{TemplateBinding VerticalAlignment}"
                                 FontFamily="{TemplateBinding FontFamily}"
                                 FontSize="{TemplateBinding FontSize}"
                                 FontWeight="{TemplateBinding FontWeight}"
                                 Foreground="{TemplateBinding Foreground}"
                                 IsEnabled="{Binding CanEditText,
                                                     RelativeSource={RelativeSource TemplatedParent}}"
                                 IsTabStop="{TemplateBinding IsEditable}"
                                 Style="{StaticResource AnnotationTextBoxStyle}"
                                 Text="{Binding Text,
                                                RelativeSource={RelativeSource TemplatedParent},
                                 TextAlignment="{TemplateBinding TextAlignment}"
                                 TextWrapping="Wrap" />

Also you can find info about how to apply a template to a control in code in How to generate RolloverMarkerTemplate in code topic.

Please, let us know if this helps,

Best regards,

  • Sean Clifford
    Thanks, that does help. If you don't mind I have another real quick question related to this issue. Is there any way that I can make it where a text annotation is always above the box annotations? Right now it seems to give a greater Z-Index to whatever annotation was last rendered onto the chart as the chart is panned, so I end up with some box annotations in front of the text annotation and some behind. Thanks for your help, I appreciate it. Greg
  • Andrew Burnett-Thompson
    This is an old comment but for sake of keeping the forums current - you can change ZIndex of annotations using the Panel.ZIndex property (or change their order in the AnnotationCollection). I would also suggest investigating TextAnnotation.LayoutTransform (ScaleTransform) and adjusting the scale factors to achieve the same affect.
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Another solution to make the TextAnnotation size small when the chart is resized is presented here:

Text Annotation Resizing with FontSize Binding

enter image description here

This is a very simple solution requiring just one binding per annotation plus a converter.

Hope this helps!

Best regards,

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