.net - 如何禁用 scollbar 的箭头按钮

Question

我正在尝试创建一个工具栏按钮，用于显示两个箭头按钮之间的内容。我能够使用以下代码做到这一点：

<ItemsControl 
            ScrollViewer.VerticalScrollBarVisibility="Auto"
            ItemsSource="{Binding DynamicToolbarItems}" 
            ItemTemplate="{StaticResource ItemTemplate}"
            HorizontalAlignment="Left">
            <ItemsControl.Template>
            <ControlTemplate TargetType="{x:Type ItemsControl}">
                    <ScrollViewer Focusable="false" Padding="{TemplateBinding Padding}">
                        <ScrollViewer.Template>
                            <ControlTemplate TargetType="{x:Type ScrollViewer}">
                            <Grid Background="Transparent">
                                <Grid.RowDefinitions>
                                    <RowDefinition Height="16" />
                                    <RowDefinition/>
                                    <RowDefinition Height="16" />
                                </Grid.RowDefinitions>
                                <Border Grid.Row="0" BorderThickness="0,0,0,1" BorderBrush="#666666">
                                    <Grid Margin="1" x:Name="UpGrid">
                                            <Path x:Name="UpArrowPath" Fill="#FFFFFF" Data="{StaticResource UpArrowGeometry}" Margin="-1" HorizontalAlignment="Center" VerticalAlignment="Center"/>
                                        <RepeatButton x:Name="RepeatButtonUp" Command="{x:Static ScrollBar.LineUpCommand}" Opacity="0"/>
                                        <RepeatButton x:Name="RepeatButtonPageUp" Command="{x:Static ScrollBar.PageUpCommand}" Visibility="Hidden"/>
                                    </Grid>
                                </Border>
                                <ScrollContentPresenter  Grid.Row="1" x:Name="PART_ScrollContentPresenter" CanContentScroll="{TemplateBinding CanContentScroll}" CanHorizontallyScroll="False" CanVerticallyScroll="False" ContentTemplate="{TemplateBinding ContentTemplate}" Content="{TemplateBinding Content}" Margin="{TemplateBinding Padding}"/>
                                <Border Grid.Row="2" BorderThickness="0,1,0,0" BorderBrush="#666666">
                                    <Grid Margin="1" x:Name="DownGrid">
                                            <Path x:Name="DownArrowPath" Data="{StaticResource DownArrowGeometry}" Margin="-1" HorizontalAlignment="Center" VerticalAlignment="Center" Fill="#FFFFFF"/>
                                        <RepeatButton x:Name="RepeatButtonDown" Command="{x:Static ScrollBar.LineDownCommand}" Opacity="0" />
                                        <RepeatButton x:Name="RepeatButtonPageDown" Command="{x:Static ScrollBar.PageDownCommand}" Visibility="Hidden"/>
                                    </Grid>
                                </Border>
                            </Grid>
                            <ControlTemplate.Triggers>
                                <MultiTrigger>
                                </MultiTrigger>
                                <Trigger SourceName="UpGrid" Property="IsMouseOver" Value="True">
                                    <Setter TargetName="UpArrowPath" Property="Fill" Value="#02abf2" />
                                </Trigger>
                                <Trigger SourceName="DownGrid" Property="IsMouseOver" Value="True">
                                    <Setter TargetName="DownArrowPath" Property="Fill" Value="#02abf2" />
                                </Trigger>
                                <!--Trigger SourceName="RepeatButtonPageUp" Property="IsEnabled" Value="False">
                                    <Setter TargetName="UpArrowPath" Property="Fill" Value="Red" />
                                </Trigger>
                                <Trigger SourceName="RepeatButtonPageDown" Property="IsEnabled" Value="False">
                                    <Setter TargetName="DownArrowPath" Property="Fill" Value="Red" />
                                </Trigger-->
                            </ControlTemplate.Triggers>
                            </ControlTemplate>
                        </ScrollViewer.Template>
                        <ItemsPresenter SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}"/>
                    </ScrollViewer>
                <ControlTemplate.Triggers>
                    <Trigger Property="IsGrouping" Value="true">
                        <Setter Property="ScrollViewer.CanContentScroll" Value="false"/>
                    </Trigger>
                </ControlTemplate.Triggers>
            </ControlTemplate>
        </ItemsControl.Template>
            <ItemsControl.GroupStyle>
                <GroupStyle HidesIfEmpty="True">
                    <GroupStyle.HeaderTemplate>
                        <DataTemplate>
                            <Separator x:Name="Separator" Style="{StaticResource ToolbarSeparatorStyle}"/>
                            <DataTemplate.Triggers>
                                <DataTrigger Binding="{Binding RelativeSource={RelativeSource PreviousData}}" Value="{x:Null}">
                                    <Setter TargetName="Separator" Property="Visibility" Value="Collapsed"/>
                                </DataTrigger>
                            </DataTemplate.Triggers>
                        </DataTemplate>
                    </GroupStyle.HeaderTemplate>
                </GroupStyle>
            </ItemsControl.GroupStyle>
    </ItemsControl>

我唯一的问题是，当您无法再滚动时，我想更改箭头按钮的填充颜色。在代码中，您可以看到我有两个注释掉的触发器：

<!--Trigger SourceName="RepeatButtonPageUp" Property="IsEnabled" Value="False">
                                <Setter TargetName="UpArrowPath" Property="Fill" Value="Red" />
                            </Trigger>
                            <Trigger SourceName="RepeatButtonPageDown" Property="IsEnabled" Value="False">
                                <Setter TargetName="DownArrowPath" Property="Fill" Value="Red" />
                            </Trigger-->

我认为这不起作用，因为当没有可滚动的内容时，RepeatButtons 不会被禁用。

我该如何实施？

谢谢！