#822 – Deciding which TextFormattingMode to Use

The TextOptions.TextFormattingMode property indicates whether fonts should be formatted using the standard WPF algorithm or the legacy GDI method for positioning the individual glyphs in the font.  The property can have one of the following values:

  • Ideal – Default value, formats text using the standard WPF method.  Glyph shapes are preserved, independent of their final position on the display
  • Display – Positions edges of glyphs on pixel boundaries.  Can result in clearer edges of text.

You should use the value of Ideal, except for the situations listed below.

Set TextFormattingMode to Display when all of the following is true:

  • The FontSize of the text is 14 or less  (small text)
  • Text is not being transformed (scaled, rotated, translated)
  • The exact shape of the glyphs is not critical (e.g. for some graphic design scenario)
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#821 – Use TextFormattingMode to Make Text Look More Clear

WPF tries to retain the exact shape and style of each glyph in a font, no matter what size the font is being rendered at.  This means that as the text gets smaller, relative to the pixel density of the display, the edges of the glyphs may no longer occur at pixel boundaries.  When this happens, WPF will use anti-aliasing to render the edges of the glyphs in a different color.  This can lead to small text looking fuzzy, or having some odd color fragments along the edges of the letters.

To avoid fuzzy text at small sizes, you can set the TextOptions.TextFormattingMode property to Display (as opposed to the default value of Ideal).  This tells WPF to align the glyphs at pixel boundaries, which can lead to crisper/cleaner text.

        <TextBlock Text="WiWi WIWI HaHaHa (Ideal = Default)"
                   Margin="5"/>
        <TextBlock Text="WiWi WIWI HaHaHa (Display)"
                   TextOptions.TextFormattingMode="Display"
                   Margin="5"/>

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