fix(combobox): PlaceholderText not displaying

unoplatform · Aug 25, 2020 · c4c1109 · c4c1109
1 parent 8ef6ac4
commit c4c1109
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Showing 2 changed files with 53 additions and 19 deletions.
diff --git a/src/Uno.UI/UI/Xaml/Controls/ComboBox/ComboBox.cs b/src/Uno.UI/UI/Xaml/Controls/ComboBox/ComboBox.cs
@@ -43,9 +43,12 @@ public partial class ComboBox : ListViewBase // TODO: Selector
 		public event EventHandler<object> DropDownClosed;
 		public event EventHandler<object> DropDownOpened;
 
+		private bool _areItemTemplatesForwarded = false;
+
 		private IPopup _popup;
 		private Border _popupBorder;
 		private ContentPresenter _contentPresenter;
+		private TextBlock _placeholderTextBlock;
 		private ContentPresenter _headerContentPresenter;
 
 		/// <summary>
@@ -79,6 +82,7 @@ protected override void OnApplyTemplate()
 			_popup = this.GetTemplateChild("Popup") as IPopup;
 			_popupBorder = this.GetTemplateChild("PopupBorder") as Border;
 			_contentPresenter = this.GetTemplateChild("ContentPresenter") as ContentPresenter;
+			_placeholderTextBlock = this.GetTemplateChild("PlaceholderTextBlock") as TextBlock;
 
 			if (_popup is PopupBase popup)
 			{
@@ -93,18 +97,7 @@ protected override void OnApplyTemplate()
 
 			if (_contentPresenter != null)
 			{
-				_contentPresenter.SetBinding(
-					ContentPresenter.ContentTemplateProperty,
-					new Binding(new PropertyPath("ItemTemplate"), null)
-					{
-						RelativeSource = RelativeSource.TemplatedParent
-					});
-				_contentPresenter.SetBinding(
-					ContentPresenter.ContentTemplateSelectorProperty,
-					new Binding(new PropertyPath("ItemTemplateSelector"), null)
-					{
-						RelativeSource = RelativeSource.TemplatedParent
-					});
+				_contentPresenter.SynchronizeContentWithOuterTemplatedParent = false;
 
 				_contentPresenter.DataContextChanged += (snd, evt) =>
 				{
@@ -248,10 +241,11 @@ internal override void OnItemClicked(int clickedIndex)
 
 		private void UpdateContentPresenter()
 		{
-			if (_contentPresenter != null)
+			if (_contentPresenter == null) return;
+
+			if (SelectedItem != null)
 			{
 				var item = GetSelectionContent();
-
 				var itemView = item as _View;
 
 				if (itemView != null)
@@ -273,12 +267,34 @@ private void UpdateContentPresenter()
 				}
 
 				_contentPresenter.Content = item;
-
 				if (itemView != null && itemView.GetVisualTreeParent() != _contentPresenter)
 				{
 					// Item may have been put back in list, reattach it to _contentPresenter
 					_contentPresenter.AddChild(itemView);
 				}
+				if (!_areItemTemplatesForwarded)
+				{
+					SetContentPresenterBinding(ContentPresenter.ContentTemplateProperty, nameof(ItemTemplate));
+					SetContentPresenterBinding(ContentPresenter.ContentTemplateSelectorProperty, nameof(ItemTemplateSelector));
+
+					_areItemTemplatesForwarded = true;
+				}
+			}
+			else
+			{
+				_contentPresenter.Content = _placeholderTextBlock;
+				if (_areItemTemplatesForwarded)
+				{
+					_contentPresenter.ClearValue(ContentPresenter.ContentTemplateProperty);
+					_contentPresenter.ClearValue(ContentPresenter.ContentTemplateSelectorProperty);
+
+					_areItemTemplatesForwarded = false;
+				}
+			}
+
+			void SetContentPresenterBinding(DependencyProperty targetProperty, string sourcePropertyPath)
+			{
+				_contentPresenter.SetBinding(targetProperty, new Binding(sourcePropertyPath) { RelativeSource = RelativeSource.TemplatedParent });
 			}
 		}
 

diff --git a/src/Uno.UI/UI/Xaml/Controls/ContentPresenter/ContentPresenter.cs b/src/Uno.UI/UI/Xaml/Controls/ContentPresenter/ContentPresenter.cs
@@ -53,6 +53,12 @@ private void InitializeContentPresenter()
 		{
 		}
 
+		/// <summary>
+		/// Indicates if the content should inherit templated parent from the presenter, or its templated parent.
+		/// </summary>
+		/// <remarks>Clear this flag to let the control nested directly under this ContentPresenter to inherit the correct templated parent</remarks>
+		internal bool SynchronizeContentWithOuterTemplatedParent { get; set; } = true;
+
 		/// <summary>
 		/// Determines if the current ContentPresenter is hosting a native control.
 		/// </summary>
@@ -695,11 +701,23 @@ private void SynchronizeContentTemplatedParent()
 			{
 				if (_contentTemplateRoot is IFrameworkElement binder)
 				{
-					var templatedParent = _contentTemplateRoot is ImplicitTextBlock
-						? this // ImplicitTextBlock is a special case that requires its TemplatedParent to be the ContentPresenter
-						: (this.TemplatedParent as IFrameworkElement)?.TemplatedParent;
+					binder.TemplatedParent = FindTemplatedParent();
 
-					binder.TemplatedParent = templatedParent;
+					DependencyObject FindTemplatedParent()
+					{
+						// ImplicitTextBlock is a special case that requires its TemplatedParent to be the ContentPresenter
+						if (_contentTemplateRoot is ImplicitTextBlock) return this;
+
+						// Sometimes when content is a child view defined in the xaml, the direct TemplatedParent should be used,
+						// but only if the content hasnt been overwritten yet. If the content has been overwritten,
+						// either ImplicitTextBlock or the DataTemplate (requiring the outter TemplatedParent) would has been used.
+						if (!SynchronizeContentWithOuterTemplatedParent && _dataTemplateUsedLastUpdate == null)
+						{
+							return this.TemplatedParent;
+						}
+
+						return (this.TemplatedParent as IFrameworkElement)?.TemplatedParent;
+					}
 				}
 				else if (_contentTemplateRoot is DependencyObject dependencyObject)
 				{