Text field focus fix (#1724)

* Added in a template binding to the background property in the MaterialDesignDatePicker, this now makes it so when setting Background on a datepicker it will reflect the change.

* Change the clear buttons on the ComboBox, PasswordBox and the TextBox to not allow focussing any longer. Fixes #1464

Author: ColossalMoose

MaterialDesignThemes.Wpf/Themes/MaterialDesignTheme.ComboBox.xaml

@@ -471,7 +471,7 @@
                             Opacity="{Binding Path=(wpf:HintAssist.HintOpacity), RelativeSource={RelativeSource TemplatedParent}}"
                             Text="{Binding Path=(wpf:TextFieldAssist.SuffixText), RelativeSource={RelativeSource TemplatedParent}}"
                             />
-                        <Button x:Name="PART_ClearButton" Height="Auto" Padding="2,0,-6,0" Style="{DynamicResource MaterialDesignToolButton}">
+                        <Button x:Name="PART_ClearButton" Height="Auto" Padding="2,0,-6,0" Style="{DynamicResource MaterialDesignToolButton}" Focusable="False">
                             <Button.Visibility>
                                 <MultiBinding Converter="{StaticResource ClearTextConverter}">
                                     <Binding ElementName="Hint" Path="IsContentNullOrEmpty" Converter="{StaticResource NotConverter}"/>
@@ -781,7 +781,7 @@
                             Opacity="{Binding Path=(wpf:HintAssist.HintOpacity), RelativeSource={RelativeSource TemplatedParent}}"
                             Text="{Binding Path=(wpf:TextFieldAssist.SuffixText), RelativeSource={RelativeSource TemplatedParent}}"
                             />
-                        <Button x:Name="PART_ClearButton" Height="Auto" Padding="2,0,-6,0" Style="{DynamicResource MaterialDesignToolButton}">
+                        <Button x:Name="PART_ClearButton" Height="Auto" Padding="2,0,-6,0" Style="{DynamicResource MaterialDesignToolButton}" Focusable="false">
                             <Button.Visibility>
                                 <MultiBinding Converter="{StaticResource ClearTextConverter}">
                                     <Binding ElementName="Hint" Path="IsContentNullOrEmpty" Converter="{StaticResource NotConverter}"/>

MaterialDesignThemes.Wpf/Themes/MaterialDesignTheme.PasswordBox.xaml

@@ -132,7 +132,7 @@
                                                 </Border>
                                             </wpf:SmartHint.Hint>
                                         </wpf:SmartHint>
-                                <Button x:Name="PART_ClearButton" Height="Auto" Grid.Column="1" Padding="2,0,0,0" 
+                                        <Button x:Name="PART_ClearButton" Height="Auto" Grid.Column="1" Padding="2,0,0,0" Focusable="false"
                                             Style="{DynamicResource MaterialDesignToolButton}" VerticalAlignment="Top">
                                     <Button.Visibility>
                                         <MultiBinding Converter="{StaticResource ClearTextConverter}">

MaterialDesignThemes.Wpf/Themes/MaterialDesignTheme.TextBox.xaml

@@ -139,7 +139,7 @@
                                                    Opacity="{Binding Path=(wpf:HintAssist.HintOpacity), RelativeSource={RelativeSource TemplatedParent}}"
                                                    Text="{Binding Path=(wpf:TextFieldAssist.SuffixText), RelativeSource={RelativeSource TemplatedParent}}"
                                                    />
-                                            <Button x:Name="PART_ClearButton" Height="Auto" Padding="2,0,0,0"
+                                            <Button x:Name="PART_ClearButton" Height="Auto" Padding="2,0,0,0" Focusable="False"
                                                 Style="{DynamicResource MaterialDesignToolButton}">
                                             <Button.Visibility>
                                                 <MultiBinding Converter="{StaticResource ClearTextConverter}">