only show toolbar overflow button if necessary

Author: ButchersBoy

MaterialDesignThemes.Wpf/Themes/MaterialDesignTheme.ToolBar.xaml

@@ -12,6 +12,8 @@
         <ResourceDictionary Source="pack://application:,,,/MaterialDesignThemes.Wpf;component/Themes/materialdesigntheme.ToggleButton.xaml" />
         <ResourceDictionary Source="pack://application:,,,/MaterialDesignThemes.Wpf;component/Themes/materialdesigntheme.Font.xaml" />
     </ResourceDictionary.MergedDictionaries>
+
+    <BooleanToVisibilityConverter x:Key="BooleanToVisibilityConverter" />
 
     <Style x:Key="MaterialDesignToolBarVerticalOverflowButtonStyle" TargetType="{x:Type ToggleButton}">
         <Setter Property="Background" Value="{DynamicResource MaterialDesignPaper}"/>
@@ -125,7 +127,10 @@
                 <ControlTemplate TargetType="{x:Type ToolBar}">
                     <DockPanel x:Name="Grid" Margin="3,1,1,1" SnapsToDevicePixels="true" Background="{TemplateBinding Background}">
                         <Grid DockPanel.Dock="Right" x:Name="OverflowGrid" HorizontalAlignment="Right">
-                            <ToggleButton x:Name="OverflowButton" ClickMode="Press" FocusVisualStyle="{x:Null}" IsChecked="{Binding IsOverflowOpen, Mode=TwoWay, RelativeSource={RelativeSource TemplatedParent}}" IsEnabled="{TemplateBinding HasOverflowItems}" Style="{StaticResource MaterialDesignToolBarHorizontalOverflowButtonStyle}"
+                            <ToggleButton x:Name="OverflowButton" ClickMode="Press" FocusVisualStyle="{x:Null}" 
+                                          IsChecked="{Binding IsOverflowOpen, Mode=TwoWay, RelativeSource={RelativeSource TemplatedParent}}" 
+                                          Visibility="{Binding RelativeSource={RelativeSource TemplatedParent}, Path=HasOverflowItems, Converter={StaticResource BooleanToVisibilityConverter}}" 
+                                          Style="{StaticResource MaterialDesignToolBarHorizontalOverflowButtonStyle}"
                                           Foreground="{TemplateBinding Foreground}"
                                           />
                             <Popup x:Name="OverflowPopup" AllowsTransparency="true" Focusable="false" IsOpen="{Binding IsOverflowOpen, RelativeSource={RelativeSource TemplatedParent}}" PopupAnimation="{DynamicResource {x:Static SystemParameters.ComboBoxPopupAnimationKey}}" Placement="Bottom" StaysOpen="false" Margin="1">