How do you determine the width of the text in a WPF TreeViewItem at run time?

Question

How do you determine the width of the text in a WPF TreeViewItem at run time?

I need to calculate an offset so I can draw a line from one leaf to the leaf of a different TreeView. All the 'width' properties return a size that is way bigger than the space taken up by the actual text of the node. It must be possible because the Select feature doesn't highlight the entire row. I'm writing the client in WPF and Silverlight.

Answer 1

You weren't very specific on the text or the tags, so I'm assuming you're taking about the .Net Framework's TreeViewItem.

There might be easier ways, but one possibility is to use the Graphics.MeasureString method. It gives you the size in pixels of a text when drawn using a specific font.

Answer 2

I have two solutions:

A) Uses the visual tree

    TreeViewItem selected = (TreeViewItem)dataSourceTreeView.SelectedItem;
    double textWidth = 0;
    double expanderWidth = 0;
    Grid grid = (Grid)VisualTreeHelper.GetChild(selected, 0);

    ToggleButton toggleButton = (ToggleButton)VisualTreeHelper.GetChild(grid, 0);
    expanderWidth = toggleButton.ActualWidth;

    Border bd = (Border)VisualTreeHelper.GetChild(grid, 1);
    textWidth = bd.ActualWidth;

B) If you don't want to use the visual tree

    TreeViewItem selected = (TreeViewItem)dataSourceTreeView.SelectedItem;
    double textWidth = 0;
    Typeface typeface = new Typeface(selected.FontFamily,
        selected.FontStyle, selected.FontWeight, selected.FontStretch);

    GlyphTypeface glyphTypeface;
    if (!typeface.TryGetGlyphTypeface(out glyphTypeface))
            throw new InvalidOperationException("No glyphtypeface found");

    string headerText = (string)selected.Header;
    double size = selected.FontSize;

    ushort[] glyphIndexes = new ushort[headerText.Length];
    double[] advanceWidths = new double[headerText.Length];

    for (int n = 0; n < headerText.Length; n++)
    {
            ushort glyphIndex = glyphTypeface.CharacterToGlyphMap[headerText[n]];
            glyphIndexes[n] = glyphIndex;

            double width = glyphTypeface.AdvanceWidths[glyphIndex] * size;
            advanceWidths[n] = width;

            textWidth += width;
    }

Answer 3

@mrphil: Sweet Zombie Jesus, that's scary

myTreeViewItem.Measure(new Size(Double.PositiveInfinity, Double.PositiveInfinity));
Size s = myTreeViewItem.DesiredSize;
return s.Width;