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
-    {
-        private TextView _textView;
-        private int _maxLength;
-
-        public ScrolledTextView()
-        {
-            ShadowType = ShadowType.In;
-            HscrollbarPolicy = PolicyType.Never;
-            VscrollbarPolicy = PolicyType.Always;
-
-            _textView = new TextView
-            {
-                AcceptsTab = false,
-                WrapMode = WrapMode.WordChar
-            };
-
-            _textView.Buffer.InsertText += InsertText;
-            Add(_textView);
-        }
-
-        public TextView TextView => _textView;
-
-        public void SetMaxLength(int maxLength)
-        {
-            _maxLength = maxLength;
-
-			if (_textView.Buffer.CharCount > maxLength)
-				_textView.Buffer.Text = _textView.Buffer.Text.Substring(0, maxLength);
-        }
-
-        protected override void OnFocusGrabbed()
-        {
-            _textView?.GrabFocus();
-        }
-
-        void InsertText(object o, InsertTextArgs args)
-        {
-            args.RetVal = args.Length <= _maxLength;
-        }
-    }
+	public class ScrolledTextView : EventBox
+	{
+		private Table _table;
+		private ScrolledWindow _scrolledWindow;
+		private Gtk.Label _placeholder;
+		private EventBox _placeholderContainer;
+		private int _maxLength;
+
+		public ScrolledTextView()
+		{
+			_table = new Table(1, 1, true);
+
+			TextView = new TextView
+			{
+				AcceptsTab = false,
+				WrapMode = WrapMode.WordChar
+			};
+
+			TextView.Buffer.InsertText += InsertText;
+			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 { 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)
+				TextView.Buffer.Text = TextView.Buffer.Text.Substring(0, maxLength);
+		}
+
+		protected override void OnFocusGrabbed()
+		{
+			TextView?.GrabFocus();
+		}
+
+		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();
+			}
+		}
+	}
 }