在特定阈值下调整wpf控件大小时不需要的剪辑

Question

在WPF中开发自定义控件时，我发现了一个奇怪的剪辑行为。当我在一定的最小边界/ tress-hold下调整控件的大小时，它决定剪切控件的前24个像素，原因我不明白。

如果有人能够解释如何在没有剪切行为的情况下实现所需的图形效果，将会非常感激。

以下XAML会发生此行为。请注意，XAML是一个精简版，使其符合标准的.net 4.0控件。

        <Style x:Key="{ComponentResourceKey ResourceId=DataGridSelectAllButtonStyle, TypeInTargetAssembly={x:Type DataGrid}}" TargetType="{x:Type Button}">
        <Setter Property="Template">
            <Setter.Value>
                <ControlTemplate TargetType="{x:Type Button}">
                    <Grid>
                        <Rectangle x:Name="Border" Fill="{DynamicResource {x:Static SystemColors.ControlBrushKey}}" SnapsToDevicePixels="True"/>
                        <Polygon x:Name="Arrow" Fill="Black" HorizontalAlignment="Right" Margin="8,8,3,3" Opacity="0.15" Points="0,10 10,10 10,0" Stretch="Uniform" VerticalAlignment="Bottom"/>
                    </Grid>
                    <ControlTemplate.Triggers>
                        <Trigger Property="IsMouseOver" Value="True">
                            <Setter Property="Stroke" TargetName="Border" Value="{DynamicResource {x:Static SystemColors.ControlDarkBrushKey}}"/>
                        </Trigger>
                        <Trigger Property="IsPressed" Value="True">
                            <Setter Property="Fill" TargetName="Border" Value="{DynamicResource {x:Static SystemColors.ControlDarkBrushKey}}"/>
                        </Trigger>
                        <Trigger Property="IsEnabled" Value="False">
                            <Setter Property="Visibility" TargetName="Arrow" Value="Collapsed"/>
                        </Trigger>
                    </ControlTemplate.Triggers>
                </ControlTemplate>
            </Setter.Value>
        </Setter>
    </Style>

    <Style x:Key="DataGridStyle1" TargetType="{x:Type DataGrid}">
        <Setter Property="Background" Value="{DynamicResource {x:Static SystemColors.ControlBrushKey}}"/>
        <Setter Property="Foreground" Value="{DynamicResource {x:Static SystemColors.ControlTextBrushKey}}"/>
        <Setter Property="BorderBrush" Value="#FF688CAF"/>
        <Setter Property="BorderThickness" Value="1"/>
        <Setter Property="RowDetailsVisibilityMode" Value="VisibleWhenSelected"/>
        <Setter Property="ScrollViewer.CanContentScroll" Value="true"/>
        <Setter Property="ScrollViewer.PanningMode" Value="Both"/>
        <Setter Property="Stylus.IsFlicksEnabled" Value="False"/>
        <Setter Property="Template">
            <Setter.Value>
                <ControlTemplate TargetType="{x:Type DataGrid}">
                    <Border Background="Transparent" Margin="0,24,0,0" >
                        <Border BorderBrush="{TemplateBinding BorderBrush}" 
                                BorderThickness="{TemplateBinding BorderThickness}" 
                                Background="{TemplateBinding Background}" Padding="{TemplateBinding Padding}" 
                                SnapsToDevicePixels="True">
                            <ScrollViewer x:Name="DG_ScrollViewer" Focusable="false">
                                <ScrollViewer.Template>
                                    <ControlTemplate TargetType="{x:Type ScrollViewer}">
                                        <Grid>
                                            <Grid.ColumnDefinitions>
                                                <ColumnDefinition Width="Auto" />
                                                <ColumnDefinition Width="*" />
                                                <ColumnDefinition Width="Auto" />
                                            </Grid.ColumnDefinitions>
                                            <Grid.RowDefinitions>
                                                <RowDefinition Height="Auto"/>
                                                <RowDefinition Height="Auto"/>
                                                <RowDefinition Height="*"/>
                                                <RowDefinition Height="Auto"/>
                                            </Grid.RowDefinitions>


                                            <Button Grid.Row="0" Command="{x:Static DataGrid.SelectAllCommand}" Focusable="false" Style="{DynamicResource {ComponentResourceKey ResourceId=DataGridSelectAllButtonStyle, TypeInTargetAssembly={x:Type DataGrid}}}" Visibility="{Binding HeadersVisibility, ConverterParameter={x:Static DataGridHeadersVisibility.All}, Converter={x:Static DataGrid.HeadersVisibilityConverter}, RelativeSource={RelativeSource AncestorType={x:Type DataGrid}}}" Width="{Binding CellsPanelHorizontalOffset, RelativeSource={RelativeSource AncestorType={x:Type DataGrid}}}"/>
                                            <DataGridColumnHeadersPresenter Grid.Row="0" x:Name="PART_ColumnHeadersPresenter" Grid.Column="1" Visibility="{Binding HeadersVisibility, ConverterParameter={x:Static DataGridHeadersVisibility.Column}, Converter={x:Static DataGrid.HeadersVisibilityConverter}, RelativeSource={RelativeSource AncestorType={x:Type DataGrid}}}"/>
                                            <Grid VerticalAlignment="Top" Grid.Row="0" Grid.Column="1" Grid.ColumnSpan="1" ClipToBounds="False">
                                                <Grid.RenderTransform>
                                                    <TranslateTransform Y="-24" />
                                                </Grid.RenderTransform>
                                                <Grid.ColumnDefinitions>
                                                    <ColumnDefinition Width="{Binding NonFrozenColumnsViewportHorizontalOffset, RelativeSource={RelativeSource AncestorType={x:Type DataGrid}}}"/>
                                                    <ColumnDefinition Width="*"/>
                                                </Grid.ColumnDefinitions>
                                                <Rectangle Fill="Yellow" Grid.Row="1" Grid.ColumnSpan="3" Grid.Column="1" Height="48" />
                                            </Grid>
                                        </Grid>
                                    </ControlTemplate>
                                </ScrollViewer.Template>
                                <ItemsPresenter SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}"/>
                            </ScrollViewer>
                        </Border>
                    </Border>
                </ControlTemplate>
            </Setter.Value>
        </Setter>
        <Style.Triggers>
            <Trigger Property="IsGrouping" Value="true">
                <Setter Property="ScrollViewer.CanContentScroll" Value="false"/>
            </Trigger>
        </Style.Triggers>
    </Style>

   <DataGrid AutoGenerateColumns="False" HorizontalAlignment="Left" Margin="12,12,0,12" Name="dataGrid1" Width="868" FrozenColumnCount="2"
              ScrollViewer.HorizontalScrollBarVisibility="Visible" CanUserSortColumns="False" CanUserReorderColumns="False" 
              AreRowDetailsFrozen="True" CanUserAddRows="False" Style="{StaticResource DataGridStyle1}"
              ScrollViewer.VerticalScrollBarVisibility="Visible">
        <DataGrid.Columns>
            <DataGridTextColumn Header="Layer Name" Width="250" IsReadOnly="True" />
            <DataGridHyperlinkColumn Header="" Width="150" IsReadOnly="True" />
            <DataGridTemplateColumn  Width="*" HeaderStyle="{StaticResource DataGridColumnHeaderStyle}" IsReadOnly="True">
                <DataGridTemplateColumn.Header>                        
                    <Grid Height="18">
                        <TextBlock Text="100.0f" Margin="0,-10" />    
                    </Grid>
                </DataGridTemplateColumn.Header>
            </DataGridTemplateColumn>

        </DataGrid.Columns>     
        <DataGrid.GroupStyle>
            <GroupStyle>
                <GroupStyle.ContainerStyle>
                    <Style TargetType="{x:Type GroupItem}">
                        <Setter Property="Template">
                            <Setter.Value>
                                <ControlTemplate TargetType="{x:Type GroupItem}">
                                    <StackPanel>

                                        <TextBlock Text="test" />
                                        <ItemsPresenter />
                                    </StackPanel>
                                </ControlTemplate>
                            </Setter.Value>                                
                        </Setter>
                    </Style>                        
                </GroupStyle.ContainerStyle>
            </GroupStyle>
        </DataGrid.GroupStyle>  
    </DataGrid>

Answer 1

因此，经过几天的摆弄，我发现罪魁祸首是GetLayoutClip方法。如果控件的边界小于最小边界，则此方法仅返回剪裁几何 。

重写此行为的最简单方法是使自定义控件继承自所述基本控件。并构建新的剪裁几何体，并考虑额外的余量。