Measuring text in WPF

Question

Using WPF, what is the most efficient way to measure a large number of short strings? Specifically, I\'d like to determine the display height of each string, given uniform

Answer 1

The most low-level technique (and therefore giving the most scope for creative optimisations) is to use GlyphRuns.

It's not very well documented but I wrote up a little example here:

http://smellegantcode.wordpress.com/2008/07/03/glyphrun-and-so-forth/

The example works out the length of the string as a necessary step before rendering it.

Answer 2

You can use the DesiredSize property on a rendered TextBox to get the height and width

using System.Windows.Threading;

...

Double TextWidth = 0;
Double TextHeight = 0;
...

MyTextBox.Text = "Words to measure size of";
this.Dispatcher.BeginInvoke(
    DispatcherPriority.Background,
    new DispatcherOperationCallback(delegate(Object state) {
        var size = MyTextBox.DesiredSize;
        this.TextWidth = size.Width;
        this.TextHeight = size.Height;
        return null; 
    }
) , null);

If you have a large number of strings it may be quicker to first pre-calualte the height and width of every indiviudal letter and symbol in a given font, and then do a calculation based on the string chars. This may not be 100% acurate due to kerning etc

Answer 3

In WPF:

Remember to call Measure() on the TextBlock before reading the DesiredSize property.

If the TextBlock was created on-the-fly, and not yet shown, you have to call Measure() first, like so:

MyTextBlock.Measure(new Size(Double.PositiveInfinity, Double.PositiveInfinity));

return new Size(MyTextBlock.DesiredSize.Width, MyTextBlock.DesiredSize.Height);

In Silverlight:

No need to measure.

return new Size(TextBlock.ActualWidth, TextBlock.ActualHeight);

The complete code looks like this:

public Size MeasureString(string s) {

    if (string.IsNullOrEmpty(s)) {
        return new Size(0, 0);
    }

    var TextBlock = new TextBlock() {
        Text = s
    };

#if SILVERLIGHT
    return new Size(TextBlock.ActualWidth, TextBlock.ActualHeight);
#else
    TextBlock.Measure(new Size(Double.PositiveInfinity, Double.PositiveInfinity));

    return new Size(TextBlock.DesiredSize.Width, TextBlock.DesiredSize.Height);
#endif
}

Answer 4

It is very simple and done by FormattedText class! Try it.