wpf - 如何在具有圆角半径的边框内设置控件样式

Question

我有一个简单的窗口，其中包含一个带角半径的外边框和一个带背景的内边框。边框基本上只是我想放置在圆角外边框内的任何类型内容的占位符。

<Window x:Class="TestRunner.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="MainWindow" Height="350" Width="525" AllowsTransparency="True" 
        WindowStyle="None" Background="{x:Null}" >
    <Border BorderThickness="2" BorderBrush="Black" CornerRadius="8"  >     
           <Border Background="White">

           </Border>
    </Border>
</Window>

问题是内部控件不继承圆角，所以它在圆角的顶部绘制，如下所示:



如何调整我的外部控件，以便内部控件不要尝试在圆角上绘制。

在内部控件上设置圆角不是一个可行的选择，因为它会导致角半径的可怕重复。

Answer 1

RectangleGeometry没有 Width属性，至少在 WPF 中。

为了我的需要，我不得不创建一个 IMultiValueConverter如此处所述:https://stackoverflow.com/a/5650367/2663813

在那之后，我在拐角处仍然有问题，所以我使用了 Kent 的第二个解决方案(注意 Border.Fill 也不存在)。

这是我写的:

<Grid>
    <Border x:Name="canvasBorder" CornerRadius="5">
        <Border.Resources>
            <tools:ContentClipConverter x:Key="ContentClipConverter" />
        </Border.Resources>
        <Border.Clip>
            <MultiBinding Converter="{StaticResource ContentClipConverter}">
                <Binding Path="ActualWidth"
                RelativeSource="{RelativeSource Self}"/>
                <Binding Path="ActualHeight"
                RelativeSource="{RelativeSource Self}"/>
                <Binding Path="CornerRadius"
                RelativeSource="{RelativeSource Self}"/>
            </MultiBinding>
        </Border.Clip>
        <!-- ... -->
    </Border>
    <Border BorderBrush="Black" BorderThickness="1" CornerRadius="5" Background="Transparent" IsHitTestVisible="false" />
</Grid>

在 ContentClipConverter.cs 内部:

/// <summary>
/// Clips the content of a rounded corner border.
/// Code taken from <a href="https://stackoverflow.com/a/5650367/2663813">this topic</a>
/// </summary>
public class ContentClipConverter : IMultiValueConverter {
    /// <summary>
    /// Gets a clipping geometry for the item
    /// </summary>
    /// <param name="values">The input values</param>
    /// <param name="targetType">The parameter is not used.</param>
    /// <param name="parameter">The parameter is not used.</param>
    /// <param name="culture">The parameter is not used.</param>
    /// <returns>The clipping geometry</returns>
    public object Convert(object[] values, Type targetType, object parameter, CultureInfo culture) {
        if (values.Length == 3 && values[0] is double && values[1] is double && values[2] is CornerRadius) {
            var width = (double)values[0];
            var height = (double)values[1];

            if (width < double.Epsilon || height < double.Epsilon) {
                return Geometry.Empty;
            }

            var radius = (CornerRadius)values[2];

            // Actually we need more complex geometry, when CornerRadius has different values.
            // But let me not to take this into account, and simplify example for a common value.
            var clip = new RectangleGeometry(new Rect(0, 0, width, height), radius.TopLeft, radius.TopLeft);
            clip.Freeze();

            return clip;
        }

        return DependencyProperty.UnsetValue;
    }

    /// <summary>
    /// Not implemented
    /// </summary>
    /// <param name="value">The parameter is not used.</param>
    /// <param name="targetTypes">The parameter is not used.</param>
    /// <param name="parameter">The parameter is not used.</param>
    /// <param name="culture">The parameter is not used.</param>
    /// <returns>This function does not return anything</returns>
    public object[] ConvertBack(object value, Type[] targetTypes, object parameter, CultureInfo culture) {
        throw new NotSupportedException();
    }