your question helped me to find ShowButtonSpinner
property which I needed to hide up and down buttons
i can suggest a workaround with setting a fixed Padding
for content when buttons are hidden. Value 0,0,17,0
seems ok to me (Win7, wpf toolkit version v2.6.0.0)
<xctk:IntegerUpDown.Style>
<Style TargetType="xctk:IntegerUpDown">
<Setter Property="Padding" Value="0,0,17,0"/>
<Setter Property="ShowButtonSpinner" Value="False"/>
<Style.Triggers>
<Trigger Property="IsMouseOver" Value="True">
<Setter Property="Padding" Value="0"/>
<Setter Property="ShowButtonSpinner" Value="True"/>
</Trigger>
</Style.Triggers>
</Style>
</xctk:IntegerUpDown.Style>
another simple thing is to align text to left side via property
<xctk:IntegerUpDown TextAlignment="Left"/>