Update readonly textbox style to make it more UX friendly

PicView/Themes/Styles/TextBox.xaml

@@ -32,15 +32,28 @@
                         <Trigger Property="IsEnabled" Value="False">
                             <Setter TargetName="border" Property="Opacity" Value="0.56" />
                         </Trigger>
-                        <Trigger Property="IsMouseOver" Value="True">
-                            <Setter TargetName="border" Property="BorderBrush" Value="{DynamicResource ResourceKey=ChosenColorBrush}" />
-                        </Trigger>
+                        
+                        <MultiTrigger>
+                            <MultiTrigger.Conditions>
+                                <Condition Property="IsReadOnly" Value="False" />
+                                <Condition Property="IsMouseOver" Value="True" />
+                            </MultiTrigger.Conditions>
+                            <MultiTrigger.Setters>
+                                <Setter TargetName="border" Property="BorderBrush" Value="{DynamicResource ResourceKey=ChosenColorBrush}" />
+                            </MultiTrigger.Setters>
+                        </MultiTrigger>
+                        
                         <Trigger Property="IsMouseOver" Value="False">
                             <Setter TargetName="border" Property="BorderBrush" Value="{StaticResource ResourceKey=BorderBrush}" />
                         </Trigger>
+                        
                         <Trigger Property="IsFocused" Value="True">
                             <Setter TargetName="border" Property="BorderBrush" Value="{DynamicResource ResourceKey=ChosenColorBrush}" />
                         </Trigger>
+                        
+                        <Trigger Property="IsReadOnly" Value="True">
+                            <Setter TargetName="border" Property="Background" Value="{StaticResource BackgroundColorBrush}"  />
+                        </Trigger>
                     </ControlTemplate.Triggers>
                 </ControlTemplate>
             </Setter.Value>