refactor<TextEdit>: rewrite implementation of placeholder for TextEdit

src/Resources/Styles/ComboBox.xaml

@@ -19,10 +19,6 @@
         </ControlTemplate.Triggers>
     </ControlTemplate>
 
-    <ControlTemplate x:Key="Template.ComboBox.TextBox" TargetType="{x:Type TextBox}">
-        <Border x:Name="PART_ContentHost" Focusable="False" Background="{TemplateBinding Background}" />
-    </ControlTemplate>
-
     <Style TargetType="{x:Type ComboBox}">
         <Setter Property="SnapsToDevicePixels" Value="true" />
         <Setter Property="OverridesDefaultStyle" Value="true" />
@@ -38,7 +34,6 @@
                     <Grid>
                         <ToggleButton x:Name="ToggleButton" BorderThickness="{TemplateBinding BorderThickness}" Template="{StaticResource Template.ComboBox.ToggleButton}" Grid.Column="2" Focusable="false" ClickMode="Press" IsChecked="{Binding IsDropDownOpen, Mode=TwoWay, RelativeSource={RelativeSource TemplatedParent}}"/>
                         <ContentPresenter x:Name="ContentSite" IsHitTestVisible="False" Content="{TemplateBinding SelectionBoxItem}" ContentTemplate="{TemplateBinding SelectionBoxItemTemplate}" ContentTemplateSelector="{TemplateBinding ItemTemplateSelector}" Margin="3,3,23,3" VerticalAlignment="Center" HorizontalAlignment="Left" TextElement.Foreground="{DynamicResource Brush.FG1}"/>
-                        <TextBox x:Name="PART_EditableTextBox" Style="{x:Null}" Template="{StaticResource Template.ComboBox.TextBox}" HorizontalAlignment="Left" VerticalAlignment="Bottom" Margin="3,3,23,3" Focusable="True" Background="Transparent" Visibility="Hidden" IsReadOnly="{TemplateBinding IsReadOnly}" />
                         <Popup x:Name="Popup" Placement="Bottom" IsOpen="{TemplateBinding IsDropDownOpen}" AllowsTransparency="True" Focusable="False" PopupAnimation="Slide">
                             <Grid x:Name="DropDown" SnapsToDevicePixels="True" MinWidth="{TemplateBinding ActualWidth}" MaxHeight="{TemplateBinding MaxDropDownHeight}">
                                 <Border x:Name="DropDownBorder" BorderThickness="1" BorderBrush="{DynamicResource Brush.Accent1}" Background="{DynamicResource Brush.Contents}"/>

src/Resources/Styles/TextBox.xaml

@@ -1,7 +1,7 @@
 <ResourceDictionary xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
                     xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
                     xmlns:controls="clr-namespace:SourceGit.Views.Controls">
-    <Style x:Key="Style.TextBox" TargetType="{x:Type TextBox}">
+    <Style TargetType="{x:Type controls:TextEdit}">
         <Setter Property="SnapsToDevicePixels" Value="True"/>
         <Setter Property="OverridesDefaultStyle" Value="True"/>
         <Setter Property="FocusVisualStyle" Value="{x:Null}"/>
@@ -58,16 +58,25 @@
         </Setter>
         <Setter Property="Template">
             <Setter.Value>
-                <ControlTemplate TargetType="{x:Type TextBox}">
+                <ControlTemplate TargetType="{x:Type controls:TextEdit}">
                     <Border 
                         x:Name="Border" 
                         Background="{TemplateBinding Background}"
                         SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}"
                         BorderThickness="{TemplateBinding BorderThickness}"
-                        BorderBrush="{TemplateBinding BorderBrush}">
+                        BorderBrush="{TemplateBinding BorderBrush}"
+                        Padding="{TemplateBinding Padding}">
+                        <Grid>
+                            <TextBlock
+                                x:Name="PART_Placeholder"
+                                Margin="4,0"
+                                Text="{TemplateBinding Placeholder}"
+                                Foreground="{DynamicResource Brush.FG2}"
+                                Visibility="{TemplateBinding PlaceholderVisibility}"
+                                VerticalAlignment="Center"/>
+
                             <ScrollViewer 
                                 x:Name="PART_ContentHost"
-                            Margin="{TemplateBinding Padding}"
                                 VerticalAlignment="Center"
                                 Background="Transparent"
                                 BorderThickness="0"
@@ -75,6 +84,7 @@
                                 RenderOptions.ClearTypeHint="Enabled"
                                 CanContentScroll="True"
                                 SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}"/>
+                        </Grid>
                     </Border>
 
                     <ControlTemplate.Triggers>
@@ -82,6 +92,11 @@
                             <Setter TargetName="Border" Property="BorderBrush" Value="{DynamicResource Brush.Accent1}"/>
                         </Trigger>
                         <Trigger Property="AcceptsReturn" Value="True">
+                            <Setter TargetName="PART_Placeholder" Property="VerticalAlignment" Value="Top"/>
+                            <Setter TargetName="PART_ContentHost" Property="VerticalAlignment" Value="Top"/>
+                        </Trigger>
+                        <Trigger Property="TextWrapping" Value="Wrap">
+                            <Setter TargetName="PART_Placeholder" Property="VerticalAlignment" Value="Top"/>
                             <Setter TargetName="PART_ContentHost" Property="VerticalAlignment" Value="Top"/>
                         </Trigger>
                     </ControlTemplate.Triggers>
@@ -89,7 +104,4 @@
             </Setter.Value>
         </Setter>
     </Style>
-
-    <Style TargetType="{x:Type TextBox}" BasedOn="{StaticResource Style.TextBox}"/>
-    <Style TargetType="{x:Type controls:TextEdit}" BasedOn="{StaticResource Style.TextBox}"/>
 </ResourceDictionary>

src/Views/Controls/TextEdit.cs

@@ -1,8 +1,6 @@
-using System.Globalization;
 using System.Windows;
 using System.Windows.Controls;
 using System.Windows.Input;
-using System.Windows.Media;
 
 namespace SourceGit.Views.Controls {
 
@@ -10,8 +8,6 @@ namespace SourceGit.Views.Controls {
     ///     扩展默认TextBox
     /// </summary>
     public class TextEdit : TextBox {
-        private bool isPlaceholderShow = false;
-
         public static readonly DependencyProperty PlaceholderProperty = DependencyProperty.Register(
             "Placeholder",
             typeof(string),
@@ -23,15 +19,15 @@ namespace SourceGit.Views.Controls {
             set { SetValue(PlaceholderProperty, value); }
         }
 
-        public static readonly DependencyProperty PlaceholderBaselineProperty = DependencyProperty.Register(
-            "PlaceholderBaseline",
-            typeof(AlignmentY),
+        public static readonly DependencyProperty PlaceholderVisibilityProperty = DependencyProperty.Register(
+            "PlaceholderVisibility",
+            typeof(Visibility),
             typeof(TextEdit),
-            new PropertyMetadata(AlignmentY.Center));
+            new PropertyMetadata(Visibility.Visible));
 
-        public AlignmentY PlaceholderBaseline {
-            get { return (AlignmentY)GetValue(PlaceholderBaselineProperty); }
-            set { SetValue(PlaceholderBaselineProperty, value); }
+        public Visibility PlaceholderVisibility {
+            get { return (Visibility)GetValue(PlaceholderVisibilityProperty); }
+            set { SetValue(PlaceholderVisibilityProperty, value); }
         }
 
         public TextEdit() {
@@ -39,41 +35,8 @@ namespace SourceGit.Views.Controls {
             SelectionChanged += OnSelectionChanged;
         }
 
-        protected override void OnRender(DrawingContext dc) {
-            base.OnRender(dc);
-
-            if (string.IsNullOrEmpty(Text) && !string.IsNullOrEmpty(Placeholder)) {
-                isPlaceholderShow = true;
-
-                var text = new FormattedText(
-                    Placeholder,
-                    CultureInfo.CurrentCulture,
-                    FlowDirection.LeftToRight,
-                    new Typeface(new FontFamily(Models.Preference.Instance.General.FontFamilyWindow), FontStyle, FontWeight, FontStretch),
-                    FontSize,
-                    FindResource("Brush.FG2") as Brush,
-                    new NumberSubstitution(),
-                    TextFormattingMode.Display,
-                    VisualTreeHelper.GetDpi(this).PixelsPerDip);
-
-                switch (PlaceholderBaseline) {
-                case AlignmentY.Top:
-                    dc.DrawText(text, new Point(4, 4));
-                    break;
-                case AlignmentY.Center:
-                    dc.DrawText(text, new Point(4, ActualHeight * .5 - text.Height * .5));
-                    break;
-                default:
-                    dc.DrawText(text, new Point(4, ActualHeight - text.Height - 4));
-                    break;
-                }
-            } else {
-                isPlaceholderShow = false;
-            }
-        }
-
         private void OnTextChanged(object sender, TextChangedEventArgs e) {
-            if (string.IsNullOrEmpty(Text) || isPlaceholderShow) InvalidateVisual();
+            PlaceholderVisibility = string.IsNullOrEmpty(Text) ? Visibility.Visible : Visibility.Collapsed;
         }
 
         private void OnSelectionChanged(object sender, RoutedEventArgs e) {

src/Views/Popups/CreateTag.xaml

@@ -66,7 +66,6 @@
             Text="{Binding ElementName=me, Path=Message, Mode=TwoWay}"
             Height="56" Padding="0,2"
             AcceptsReturn="True"
-            Placeholder="{DynamicResource Text.CreateTag.Message.Placeholder}"
-            PlaceholderBaseline="Top"/>
+            Placeholder="{DynamicResource Text.CreateTag.Message.Placeholder}"/>
     </Grid>
 </controls:PopupWidget>

src/Views/Widgets/WorkingCopy.xaml

@@ -191,8 +191,9 @@
                 KeyDown="CommitMessageKeyDown"
                 ScrollViewer.HorizontalScrollBarVisibility="Disabled"
                 ScrollViewer.VerticalScrollBarVisibility="Auto"
-                Placeholder="{DynamicResource Text.WorkingCopy.CommitMessageTip}"
-                PlaceholderBaseline="Top">
+                Background="{DynamicResource Brush.Contents}"
+                BorderBrush="{DynamicResource Brush.Border2}"
+                Placeholder="{DynamicResource Text.WorkingCopy.CommitMessageTip}">
                 <TextBox.Text>
                     <Binding ElementName="me" Path="CommitMessage" Mode="TwoWay" UpdateSourceTrigger="PropertyChanged">
                         <Binding.ValidationRules>