Implemented Editor Placeholder and PlaceholderColor in GTK (#3135)

Xamarin.Forms.Platform.GTK/Controls/ScrolledTextView.cs

@@ -2,45 +2,134 @@
 
 namespace Xamarin.Forms.Platform.GTK.Controls
 {
-    public class ScrolledTextView : ScrolledWindow
+	public class ScrolledTextView : EventBox
 	{
-        private TextView _textView;
+		private Table _table;
+		private ScrolledWindow _scrolledWindow;
+		private Gtk.Label _placeholder;
+		private EventBox _placeholderContainer;
 		private int _maxLength;
 
 		public ScrolledTextView()
 		{
-            ShadowType = ShadowType.In;
+			_table = new Table(1, 1, true);
-            HscrollbarPolicy = PolicyType.Never;
-            VscrollbarPolicy = PolicyType.Always;
 
-            _textView = new TextView
+			TextView = new TextView
 			{
 				AcceptsTab = false,
 				WrapMode = WrapMode.WordChar
 			};
 
-            _textView.Buffer.InsertText += InsertText;
+			TextView.Buffer.InsertText += InsertText;
-            Add(_textView);
+			TextView.FocusOutEvent += FocusedOut;
+
+			_scrolledWindow = new ScrolledWindow
+			{
+				ShadowType = ShadowType.In,
+				HscrollbarPolicy = PolicyType.Never,
+				VscrollbarPolicy = PolicyType.Automatic
+			};
+
+			_scrolledWindow.Add(TextView);
+
+			_placeholder = new Gtk.Label();
+			_placeholder.SetAlignment(0, 0);
+
+			_placeholderContainer = new EventBox
+			{
+				BorderWidth = 2
+			};
+
+			_placeholderContainer.Add(_placeholder);
+
+			_placeholderContainer.ButtonPressEvent += PlaceHolderContainerPressed;
+
+			SetBackgroundColor(TextView.Style.BaseColors[(int)StateType.Normal]);
+
+			Add(_table);
+
+			_table.Attach(_placeholderContainer, 0, 1, 0, 1, AttachOptions.Fill, AttachOptions.Fill, 0, 0);
+			_table.Attach(_scrolledWindow, 0, 1, 0, 1);
 		}
 
-        public TextView TextView => _textView;
+		public TextView TextView { get; }
+
+		public string PlaceholderText
+		{
+			get
+			{
+				return _placeholder.Text;
+			}
+			set
+			{
+				_placeholder.Text = GLib.Markup.EscapeText(value ?? string.Empty);
+			}
+		}
+
+		public void SetBackgroundColor(Gdk.Color color)
+		{
+			ModifyBg(StateType.Normal, color);
+			TextView.ModifyBase(StateType.Normal, color);
+			_placeholderContainer.ModifyBg(StateType.Normal, color);
+		}
+
+		public void SetPlaceholderTextColor(Gdk.Color color)
+		{
+			_placeholder.ModifyFg(StateType.Normal, color);
+		}
 
 		public void SetMaxLength(int maxLength)
 		{
 			_maxLength = maxLength;
 
-			if (_textView.Buffer.CharCount > maxLength)
+			if (TextView.Buffer.CharCount > maxLength)
-				_textView.Buffer.Text = _textView.Buffer.Text.Substring(0, maxLength);
+				TextView.Buffer.Text = TextView.Buffer.Text.Substring(0, maxLength);
 		}
 
 		protected override void OnFocusGrabbed()
 		{
-            _textView?.GrabFocus();
+			TextView?.GrabFocus();
 		}
 
-        void InsertText(object o, InsertTextArgs args)
+		protected override void OnSizeAllocated(Gdk.Rectangle allocation)
+		{
+			base.OnSizeAllocated(allocation);
+
+			TextView.SetSizeRequest(allocation.Width, allocation.Height);
+
+			ShowPlaceholderIfNeeded();
+		}
+
+		private void InsertText(object o, InsertTextArgs args)
 		{
 			args.RetVal = args.Length <= _maxLength;
 		}
+
+		private void FocusedOut(object o, FocusOutEventArgs args)
+		{
+			ShowPlaceholderIfNeeded();
+		}
+
+		private void ShowPlaceholderIfNeeded()
+		{
+			if (string.IsNullOrEmpty(TextView.Buffer.Text) && !string.IsNullOrEmpty(_placeholder.Text))
+			{
+				_placeholderContainer.VisibleWindow = true;
+			}
+			else
+			{
+				_placeholderContainer.VisibleWindow = false;
+			}
+		}
+
+		private void PlaceHolderContainerPressed(object o, ButtonPressEventArgs args)
+		{
+			if (Sensitive)
+			{
+				TextView.Sensitive = true;
+				TextView.HasFocus = true;
+				TextView.GdkWindow?.Raise();
+			}
+		}
 	}
 }

Xamarin.Forms.Platform.GTK/Renderers/EditorRenderer.cs

@@ -20,10 +20,9 @@ namespace Xamarin.Forms.Platform.GTK.Renderers
 		{
 			if (!Element.BackgroundColor.IsDefaultOrTransparent())
 			{
-                var color = Element.BackgroundColor.ToGtkColor();
+				var backgroundColor = Element.BackgroundColor.ToGtkColor();
 
-                Control.TextView.ModifyBg(StateType.Normal, color);
+				Control.SetBackgroundColor(backgroundColor);
-                Control.TextView.ModifyBase(StateType.Normal, color);
 			}
 		}
 
@@ -34,6 +33,7 @@ namespace Xamarin.Forms.Platform.GTK.Renderers
 				var scrolled = new ScrolledTextView();
 
 				scrolled.TextView.Buffer.TagTable.Add(new TextTag(TextColorTagName));
+
 				scrolled.TextView.Buffer.Changed += TextViewBufferChanged;
 				scrolled.TextView.Focused += TextViewFocused;
 				scrolled.TextView.FocusOutEvent += TextViewFocusedOut;
@@ -47,6 +47,8 @@ namespace Xamarin.Forms.Platform.GTK.Renderers
 				UpdateText();
 				UpdateFont();
 				UpdateTextColor();
+				UpdatePlaceholder();
+				UpdatePlaceholderColor();
 				UpdateMaxLength();
 			}
 
@@ -61,6 +63,10 @@ namespace Xamarin.Forms.Platform.GTK.Renderers
 				UpdateText();
 			else if (e.PropertyName == Editor.TextColorProperty.PropertyName)
 				UpdateTextColor();
+			else if (e.PropertyName == Editor.PlaceholderProperty.PropertyName)
+				UpdatePlaceholder();
+			else if (e.PropertyName == Editor.PlaceholderColorProperty.PropertyName)
+				UpdatePlaceholderColor();
 			else if (e.PropertyName == Editor.FontAttributesProperty.PropertyName)
 				UpdateFont();
 			else if (e.PropertyName == Editor.FontFamilyProperty.PropertyName)
@@ -161,5 +167,23 @@ namespace Xamarin.Forms.Platform.GTK.Renderers
 		{
 			Control.SetMaxLength(Element.MaxLength);
 		}
+
+		private void UpdatePlaceholder()
+		{
+			if (Element.Placeholder != Control.PlaceholderText)
+			{
+				Control.PlaceholderText = Element.Placeholder;
+			}
+		}
+
+		private void UpdatePlaceholderColor()
+		{
+			if (!Element.PlaceholderColor.IsDefaultOrTransparent())
+			{
+				var placeholderColor = Element.PlaceholderColor.ToGtkColor();
+
+				Control.SetPlaceholderTextColor(placeholderColor);
+			}
+		}
 	}
 }