确定组合框的弹出框何时遇到屏幕边缘并更改目标原点更改为目标区域的左上角

Question

我有一个问题与弹出框的位置。如果组合框遇到屏幕边缘，则目标原点更改为目标区域的左上角，而弹出框对齐点更改为弹出框的左下角。这对我来说是个问题，因为我把组合框的样式改成了圆角。这是正常情况下的样子这是遇到屏幕边缘时的样子

我已经定义了一个样式，我试图在组合框的"放置"属性上设置触发器，但没有成功。这是我的风格:

<Style
x:Key="FormComboboxStyle"
BasedOn="{StaticResource BaseStyle}"
TargetType="ComboBox">
<Setter Property="SnapsToDevicePixels" Value="true" />
<Setter Property="OverridesDefaultStyle" Value="true" />
<Setter Property="ScrollViewer.HorizontalScrollBarVisibility" Value="Auto" />
<Setter Property="ScrollViewer.VerticalScrollBarVisibility" Value="Auto" />
<Setter Property="ScrollViewer.CanContentScroll" Value="true" />
<Setter Property="Padding"
Value="5" />
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="ComboBox">
<Grid>
<ToggleButton
Name="ToggleButton"
Template="{StaticResource ComboBoxToggleButton}"
Grid.Column="2"
Focusable="false"
IsChecked="{Binding Path=IsDropDownOpen,Mode=TwoWay,RelativeSource={RelativeSource TemplatedParent}}"
ClickMode="Press">
</ToggleButton>
<ContentPresenter
Name="ContentSite"
IsHitTestVisible="False"
Content="{TemplateBinding SelectionBoxItem}"
ContentTemplate="{TemplateBinding SelectionBoxItemTemplate}"
ContentTemplateSelector="{TemplateBinding ItemTemplateSelector}"
Margin="{TemplateBinding Padding}"
VerticalAlignment="Center"
HorizontalAlignment="Left" />
<TextBox x:Name="PART_EditableTextBox"
Style="{StaticResource ComboBoxTextBoxStyle}"
Template="{StaticResource ComboBoxTextBox}"
HorizontalAlignment="Left"
VerticalAlignment="Center"
Margin="{TemplateBinding Padding}"
Focusable="True"
Background="Transparent"
Visibility="Hidden"
IsReadOnly="{TemplateBinding IsReadOnly}" />
<Popup
Name="Popup"
IsOpen="{TemplateBinding IsDropDownOpen}"
Placement="Bottom"
AllowsTransparency="True"
Focusable="False"
VerticalOffset="0"
HorizontalOffset="0"
PopupAnimation="Slide">
<Grid
Name="DropDown"
SnapsToDevicePixels="True"
MinWidth="{TemplateBinding ActualWidth}"
MaxHeight="{TemplateBinding MaxDropDownHeight}">
<Border
x:Name="DropDownBorder"
Background="{DynamicResource WhiteColor}"
BorderThickness="2,0,2,2"
CornerRadius="0 0 5 5"
Padding="0"
BorderBrush="{DynamicResource PrimaryGrayColor}" />
<ScrollViewer Margin="4,2,4,6" SnapsToDevicePixels="True">
<StackPanel
IsItemsHost="True"
KeyboardNavigation.DirectionalNavigation="Contained" />
</ScrollViewer>
</Grid>
</Popup>
</Grid>
<ControlTemplate.Triggers>
<Trigger Property="HasItems" Value="false">
<Setter TargetName="DropDownBorder" Property="MinHeight" Value="95" />
</Trigger>
<Trigger Property="IsEnabled" Value="false">
<Setter Property="Foreground" Value="{DynamicResource DisabledPrimaryGrayColor}" />
</Trigger>
<Trigger Property="IsGrouping" Value="true">
<Setter Property="ScrollViewer.CanContentScroll" Value="false" />
</Trigger>
<Trigger SourceName="Popup" Property="Popup.AllowsTransparency" Value="true">
<Setter TargetName="DropDownBorder" Property="Margin" Value="0,0,0,0" />
</Trigger>
<Trigger Property="IsEditable"
Value="true">
<Setter Property="IsTabStop" Value="false" />
<Setter TargetName="PART_EditableTextBox" Property="Visibility"    Value="Visible" />
<Setter TargetName="ContentSite" Property="Visibility" Value="Hidden" />
</Trigger>
</ControlTemplate.Triggers>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>

Answer 1

根据当弹出窗口遇到屏幕边缘时，"出于安全考虑，不能将弹出窗口隐藏在屏幕边缘。"因此，你不能强行将弹出框放在组合框下，如果它会隐藏弹出框。