Implemented MaxLength property on Entry and Editor

Xamarin.Forms.Controls/CoreGalleryPages/EditorCoreGalleryPage.cs

@@ -35,6 +35,8 @@ protected override void Build (StackLayout stackLayout)
 			var textColorDisabledContainer = new ViewContainer<Editor> (Test.Editor.TextColor,
 				new Editor { Text = "I should have the default disabled text color", TextColor = Color.Red, IsEnabled = false });
 
+			var maxLengthContainer = new ViewContainer<Editor>(Test.Editor.MaxLength, new Editor { MaxLength = 3 });
+
 			Add (completedContainer);
 			Add (textContainer);
 			Add (textChangedContainer);
@@ -46,6 +48,7 @@ protected override void Build (StackLayout stackLayout)
 			Add (textFontSizeLargeContainer);
 			Add (textColorContainer);
 			Add (textColorDisabledContainer);
+			Add (maxLengthContainer);
 		}
 	}
 }

Xamarin.Forms.Controls/CoreGalleryPages/EntryCoreGalleryPage.cs

@@ -64,6 +64,8 @@ protected override void Build (StackLayout stackLayout)
 			var passwordColorContainer = new ViewContainer<Entry> (Test.Entry.PasswordColor,
 				new Entry { IsPassword = true, Text = "12345", TextColor = Color.Red });
 
+			var maxLengthContainer = new ViewContainer<Entry>(Test.Entry.MaxLength,	new Entry { MaxLength = 3 });
+
 			Add (isPasswordContainer);
 			Add (completedContainer);
 			Add (placeholderContainer);
@@ -87,6 +89,7 @@ protected override void Build (StackLayout stackLayout)
 			Add (textColorDisabledContainer);
 			Add (placeholderColorDisabledContainer);
 			Add (passwordColorContainer);
+			Add (maxLengthContainer);
 		}
 	}
 }

Xamarin.Forms.Core/InputView.cs

@@ -5,6 +5,14 @@ public class InputView : View
 		public static readonly BindableProperty KeyboardProperty = BindableProperty.Create("Keyboard", typeof(Keyboard), typeof(InputView), Keyboard.Default,
 			coerceValue: (o, v) => (Keyboard)v ?? Keyboard.Default);
 
+		public static readonly BindableProperty MaxLengthProperty = BindableProperty.Create(nameof(MaxLength), typeof(int), typeof(int), int.MaxValue);
+
+		public int MaxLength
+		{
+			get { return (int)GetValue(MaxLengthProperty); }
+			set { SetValue(MaxLengthProperty, value); }
+		}
+
 		internal InputView()
 		{
 		}

Xamarin.Forms.CustomAttributes/TestAttributes.cs

@@ -497,7 +497,8 @@ public enum Editor
 			TextColor,
 			FontAttributes,
 			FontFamily,
-			FontSize
+			FontSize,
+			MaxLength
 		}
 
 		public enum Entry
@@ -521,7 +522,8 @@ public enum Entry
 			PlaceholderColor,
 			TextDisabledColor,
 			PlaceholderDisabledColor,
-			PasswordColor
+			PasswordColor,
+			MaxLength
 		}
 
 		public enum Frame

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

@@ -1,5 +1,7 @@
 using System;
+using System.Collections.Generic;
 using System.ComponentModel;
+using System.Linq;
 using Android.Content;
 using Android.Content.Res;
 using Android.OS;
@@ -82,6 +84,7 @@ protected override void OnElementChanged(ElementChangedEventArgs<Editor> e)
 			UpdateInputType();
 			UpdateTextColor();
 			UpdateFont();
+			UpdateMaxLength();
 		}
 
 		protected override void OnElementPropertyChanged(object sender, PropertyChangedEventArgs e)
@@ -98,6 +101,8 @@ protected override void OnElementPropertyChanged(object sender, PropertyChangedE
 				UpdateFont();
 			else if (e.PropertyName == Editor.FontSizeProperty.PropertyName)
 				UpdateFont();
+			else if (e.PropertyName == InputView.MaxLengthProperty.PropertyName)
+				UpdateMaxLength();
 
 			base.OnElementPropertyChanged(sender, e);
 		}
@@ -177,5 +182,28 @@ void OnKeyboardBackPressed(object sender, EventArgs eventArgs)
 			ElementController?.SendCompleted();
 			Control?.ClearFocus();
 		}
+
+		void UpdateMaxLength()
+		{
+			var currentFilters = new List<IInputFilter>(Control?.GetFilters() ?? new IInputFilter[0]);
+
+			for (var i = 0; i < currentFilters.Count; i++)
+			{
+				if (currentFilters[i] is InputFilterLengthFilter)
+				{
+					currentFilters.RemoveAt(i);
+					break;
+				}
+			}
+
+			currentFilters.Add(new InputFilterLengthFilter(Element.MaxLength));
+
+			Control?.SetFilters(currentFilters.ToArray());
+
+			var currentControlText = Control?.Text;
+
+			if (currentControlText.Length > Element.MaxLength)
+				Control.Text = currentControlText.Substring(0, Element.MaxLength);
+		}
 	}
 }

Xamarin.Forms.Platform.Android/Renderers/EntryRenderer.cs

@@ -1,4 +1,5 @@
 using System;
+using System.Collections.Generic;
 using System.ComponentModel;
 using Android.Content;
 using Android.Content.Res;
@@ -83,8 +84,6 @@ protected override void OnElementChanged(ElementChangedEventArgs<Entry> e)
 				_textColorSwitcher = new TextColorSwitcher(textView.TextColors, useLegacyColorManagement);
 				_hintColorSwitcher = new TextColorSwitcher(textView.HintTextColors, useLegacyColorManagement);
 
-
-
 				SetNativeControl(textView);
 			}
 
@@ -96,6 +95,7 @@ protected override void OnElementChanged(ElementChangedEventArgs<Entry> e)
 			UpdateAlignment();
 			UpdateFont();
 			UpdatePlaceholderColor();
+			UpdateMaxLength();
 		}
 
 		protected override void Dispose(bool disposing)
@@ -117,7 +117,7 @@ protected override void Dispose(bool disposing)
 
 			base.Dispose(disposing);
 		}
-		
+
 		protected override void OnElementPropertyChanged(object sender, PropertyChangedEventArgs e)
 		{
 			if (e.PropertyName == Entry.PlaceholderProperty.PropertyName)
@@ -152,14 +152,16 @@ protected override void OnElementPropertyChanged(object sender, PropertyChangedE
 				UpdatePlaceholderColor();
 			else if (e.PropertyName == VisualElement.FlowDirectionProperty.PropertyName)
 				UpdateAlignment();
+			else if (e.PropertyName == InputView.MaxLengthProperty.PropertyName)
+				UpdateMaxLength();
 
 			base.OnElementPropertyChanged(sender, e);
 		}
 
 		protected virtual NumberKeyListener GetDigitsKeyListener(InputTypes inputTypes)
 		{
-			// Override this in a custom renderer to use a different NumberKeyListener 
-			// or to filter out input types you don't want to allow 
+			// Override this in a custom renderer to use a different NumberKeyListener
+			// or to filter out input types you don't want to allow
 			// (e.g., inputTypes &= ~InputTypes.NumberFlagSigned to disallow the sign)
 			return LocalizedDigitsKeyListener.Create(inputTypes);
 		}
@@ -207,5 +209,27 @@ void OnKeyboardBackPressed(object sender, EventArgs eventArgs)
 		{
 			Control?.ClearFocus();
 		}
+		void UpdateMaxLength()
+		{
+			var currentFilters = new List<IInputFilter>(Control?.GetFilters() ?? new IInputFilter[0]);
+
+			for (var i = 0; i < currentFilters.Count; i++)
+			{
+				if (currentFilters[i] is InputFilterLengthFilter)
+				{
+					currentFilters.RemoveAt(i);
+					break;
+				}
+			}
+
+			currentFilters.Add(new InputFilterLengthFilter(Element.MaxLength));
+
+			Control?.SetFilters(currentFilters.ToArray());
+
+			var currentControlText = Control?.Text;
+
+			if (currentControlText.Length > Element.MaxLength)
+				Control.Text = currentControlText.Substring(0, Element.MaxLength);
+		}
 	}
 }

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

@@ -76,6 +76,11 @@ public void SetFont(FontDescription fontDescription)
             _placeholder.ModifyFont(fontDescription);
         }
 
+        public void SetMaxLength(int maxLength)
+        {
+            _entry.MaxLength = maxLength;
+        }
+
         protected override void OnSizeAllocated(Gdk.Rectangle allocation)
         {
             base.OnSizeAllocated(allocation);

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

@@ -5,6 +5,7 @@ namespace Xamarin.Forms.Platform.GTK.Controls
     public class ScrolledTextView : ScrolledWindow
     {
         private TextView _textView;
+        private int _maxLength;
 
         public ScrolledTextView()
         {
@@ -18,14 +19,28 @@ public ScrolledTextView()
                 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;
+        }
     }
 }

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

@@ -47,6 +47,7 @@ protected override void OnElementChanged(ElementChangedEventArgs<Editor> e)
                 UpdateText();
                 UpdateFont();
                 UpdateTextColor();
+                UpdateMaxLength();
             }
 
             base.OnElementChanged(e);
@@ -66,6 +67,8 @@ protected override void OnElementPropertyChanged(object sender, PropertyChangedE
                 UpdateFont();
             else if (e.PropertyName == Editor.FontSizeProperty.PropertyName)
                 UpdateFont();
+            else if (e.PropertyName == InputView.MaxLengthProperty.PropertyName)
+                UpdateMaxLength();
         }
 
         protected override void Dispose(bool disposing)
@@ -153,5 +156,10 @@ private static void AdjustMinimumHeight(TextView textView, FontDescription font
                 textView.HeightRequest = minHeight;
             }
         }
+
+        private void UpdateMaxLength()
+        {
+            Control.SetMaxLength(Element.MaxLength);
+        }
     }
 }

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

@@ -4,6 +4,7 @@
 using Xamarin.Forms.Platform.GTK.Controls;
 using Xamarin.Forms.Platform.GTK.Extensions;
 using Xamarin.Forms.Platform.GTK.Helpers;
+using System;
 
 namespace Xamarin.Forms.Platform.GTK.Renderers
 {
@@ -35,6 +36,7 @@ protected override void OnElementChanged(ElementChangedEventArgs<Entry> e)
                 UpdateFont();
                 UpdateTextVisibility();
                 UpdatePlaceholder();
+                UpdateMaxLength();
             }
 
             base.OnElementChanged(e);
@@ -60,6 +62,8 @@ protected override void OnElementPropertyChanged(object sender, PropertyChangedE
                 UpdatePlaceholder();
             else if (e.PropertyName == Entry.PlaceholderColorProperty.PropertyName)
                 UpdatePlaceholder();
+            else if (e.PropertyName == InputView.MaxLengthProperty.PropertyName)
+                UpdateMaxLength();
 
             base.OnElementPropertyChanged(sender, e);
         }
@@ -148,5 +152,10 @@ private void OnKeyReleased(object o, KeyReleaseEventArgs args)
                 EntryController.SendCompleted();
             }
         }
+
+        private void UpdateMaxLength()
+        {
+            Control.SetMaxLength(Element.MaxLength);
+        }
     }
 }

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

@@ -41,6 +41,7 @@ protected override void OnElementChanged(ElementChangedEventArgs<Editor> e)
 			UpdateFont();
 			UpdateTextColor();
 			UpdateEditable();
+			UpdateMaxLength();
 		}
 
 		protected override void OnElementPropertyChanged(object sender, PropertyChangedEventArgs e)
@@ -59,6 +60,8 @@ protected override void OnElementPropertyChanged(object sender, PropertyChangedE
 				UpdateFont();
 			else if (e.PropertyName == Editor.FontSizeProperty.PropertyName)
 				UpdateFont();
+			else if (e.PropertyName == InputView.MaxLengthProperty.PropertyName)
+				UpdateMaxLength();
 		}
 
 		protected override void SetBackgroundColor(Color color)
@@ -88,6 +91,8 @@ protected override void Dispose(bool disposing)
 
 		void HandleChanged(object sender, EventArgs e)
 		{
+			UpdateMaxLength();
+
 			ElementController.SetValueFromRenderer(Editor.TextProperty, Control.StringValue);
 		}
 
@@ -124,5 +129,13 @@ void UpdateTextColor()
 
 			Control.TextColor = textColor.IsDefault ? NSColor.Black : textColor.ToNSColor();
 		}
+
+		void UpdateMaxLength()
+		{
+			var currentControlText = Control?.StringValue;
+
+			if (currentControlText.Length > Element?.MaxLength)
+				Control.StringValue = currentControlText.Substring(0, Element.MaxLength);
+		}
 	}
 }