Avalonia/tests/Avalonia.Controls.UnitTests/Presenters/ContentPresenterTests_InTemplate.cs

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Reactive.Linq;
using Avalonia.Controls.Presenters;
using Avalonia.Controls.Templates;
using Avalonia.Data;
using Avalonia.LogicalTree;
using Avalonia.Styling;
using Avalonia.UnitTests;
using Avalonia.VisualTree;
using Xunit;

namespace Avalonia.Controls.UnitTests.Presenters
{
    /// <summary>
    /// Tests for ContentControls that are hosted in a control template.
    /// </summary>
    public class ContentPresenterTests_InTemplate : ScopedTestBase
    {
        [Fact]
        public void Should_Register_With_Host_When_TemplatedParent_Set()
        {
            var host = new ContentControl();
            var target = new ContentPresenter { Name = "PART_ContentPresenter" };

            Assert.Null(host.Presenter);

            target.TemplatedParent = host;

            Assert.Same(target, host.Presenter);
        }

        [Fact]
        public void Setting_Content_To_Control_Should_Set_Child()
        {
            var (target, _) = CreateTarget();
            var child = new Border();

            target.Content = child;

            Assert.Equal(child, target.Child);
        }

        [Fact]
        public void Setting_Content_To_Control_Should_Update_Logical_Tree()
        {
            var (target, parent) = CreateTarget();
            var child = new Border();

            target.Content = child;

            Assert.Equal(parent, child.GetLogicalParent());
            Assert.Equal(new[] { child }, parent.GetLogicalChildren());
        }

        [Fact]
        public void Setting_Content_To_Control_Should_Update_Visual_Tree()
        {
            var (target, _) = CreateTarget();
            var child = new Border();

            target.Content = child;

            Assert.Equal(target, child.GetVisualParent());
            Assert.Equal(new[] { child }, target.GetVisualChildren());
        }

        [Fact]
        public void Setting_Content_To_String_Should_Create_TextBlock()
        {
            var (target, _) = CreateTarget();

            target.Content = "Foo";

            Assert.IsType<TextBlock>(target.Child);
            Assert.Equal("Foo", ((TextBlock)target.Child).Text);
        }

        [Fact]
        public void Setting_Content_To_String_Should_Update_Logical_Tree()
        {
            var (target, parent) = CreateTarget();

            target.Content = "Foo";

            var child = target.Child;
            Assert.NotNull(child);
            Assert.Equal(parent, child.GetLogicalParent());
            Assert.Equal(new[] { child }, parent.GetLogicalChildren());
        }

        [Fact]
        public void Setting_Content_To_String_Should_Update_Visual_Tree()
        {
            var (target, _) = CreateTarget();

            target.Content = "Foo";

            var child = target.Child;
            Assert.NotNull(child);
            Assert.Equal(target, child.GetVisualParent());
            Assert.Equal(new[] { child }, target.GetVisualChildren());
        }

        [Fact]
        public void Clearing_Control_Content_Should_Update_Logical_Tree()
        {
            var (target, _) = CreateTarget();
            var child = new Border();

            target.Content = child;
            target.Content = null;

            Assert.Null(child.GetLogicalParent());
            Assert.Empty(target.GetLogicalChildren());
        }

        [Fact]
        public void Clearing_Control_Content_Should_Update_Visual_Tree()
        {
            var (target, _) = CreateTarget();
            var child = new Border();

            target.Content = child;
            target.Content = null;

            Assert.Null(child.GetVisualParent());
            Assert.Empty(target.GetVisualChildren());
        }

        [Fact]
        public void Control_Content_Should_Not_Be_NameScope()
        {
            var (target, _) = CreateTarget();

            target.Content = new TextBlock();

            Assert.IsType<TextBlock>(target.Child);
            Assert.Null(NameScope.GetNameScope((Control)target.Child));
        }

        [Fact]
        public void Assigning_Control_To_Content_Should_Not_Set_DataContext()
        {
            var (target, _) = CreateTarget();
            target.Content = new Border();

            Assert.False(target.IsSet(Control.DataContextProperty));
        }

        [Fact]
        public void Assigning_NonControl_To_Content_Should_Set_DataContext_On_UpdateChild()
        {
            var (target, _) = CreateTarget();
            target.Content = "foo";

            Assert.Equal("foo", target.DataContext);
        }

        [Fact]
        public void Should_Use_ContentTemplate_If_Specified()
        {
            var (target, _) = CreateTarget();

            target.ContentTemplate = new FuncDataTemplate<string>((_, __) => new Canvas());
            target.Content = "Foo";

            Assert.IsType<Canvas>(target.Child);
        }

        [Fact]
        public void Should_Update_If_ContentTemplate_Changed()
        {
            var (target, _) = CreateTarget();

            target.Content = "Foo";
            Assert.IsType<TextBlock>(target.Child);

            target.ContentTemplate = new FuncDataTemplate<string>((_, __) => new Canvas());
            Assert.IsType<Canvas>(target.Child);

            target.ContentTemplate = null;
            Assert.IsType<TextBlock>(target.Child);
        }

        [Fact]
        public void Assigning_Control_To_Content_After_NonControl_Should_Clear_DataContext()
        {
            var (target, _) = CreateTarget();

            target.Content = "foo";

            Assert.True(target.IsSet(Control.DataContextProperty));

            target.Content = new Border();

            Assert.False(target.IsSet(Control.DataContextProperty));
        }

        [Fact]
        public void Recycles_DataTemplate()
        {
            var (target, _) = CreateTarget();
            target.DataTemplates.Add(new FuncDataTemplate<string>((_, __) => new Border(), true));

            target.Content = "foo";

            var control = target.Child;
            Assert.IsType<Border>(control);

            target.Content = "bar";
            Assert.Same(control, target.Child);
        }

        [Fact]
        public void Detects_DataTemplate_Doesnt_Match_And_Doesnt_Recycle()
        {
            var (target, _) = CreateTarget();
            target.DataTemplates.Add(new FuncDataTemplate<string>(x => x == "foo", _ => new Border(), true));

            target.Content = "foo";

            var control = target.Child;
            Assert.IsType<Border>(control);

            target.Content = "bar";
            Assert.IsType<TextBlock>(target.Child);
        }

        [Fact]
        public void Detects_DataTemplate_Doesnt_Support_Recycling()
        {
            var (target, _) = CreateTarget();
            target.DataTemplates.Add(new FuncDataTemplate<string>((_, __) => new Border(), false));

            target.Content = "foo";

            var control = target.Child;
            Assert.IsType<Border>(control);

            target.Content = "bar";
            Assert.NotSame(control, target.Child);
        }

        [Fact]
        public void Reevaluates_DataTemplates_When_Recycling()
        {
            var (target, _) = CreateTarget();

            target.DataTemplates.Add(new FuncDataTemplate<string>(x => x == "bar", _ => new Canvas(), true));
            target.DataTemplates.Add(new FuncDataTemplate<string>((_, __) => new Border(), true));

            target.Content = "foo";

            var control = target.Child;
            Assert.IsType<Border>(control);

            target.Content = "bar";
            Assert.IsType<Canvas>(target.Child);
        }

        [Fact]
        public void Should_Not_Bind_Old_Child_To_New_DataContext()
        {
            // Test for issue #1099.
            var textBlock = new TextBlock
            {
                [!TextBlock.TextProperty] = new Binding(),
            };

            var (target, host) = CreateTarget();
            host.DataTemplates.Add(new FuncDataTemplate<string>((_, __) => textBlock));
            host.DataTemplates.Add(new FuncDataTemplate<int>((_, __) => new Canvas()));

            target.Content = "foo";
            Assert.Same(textBlock, target.Child);

            textBlock.PropertyChanged += (s, e) =>
            {
                Assert.NotEqual(e.NewValue, "42");
            };

            target.Content = 42;
        }

        [Fact]
        public void Should_Not_Bind_Child_To_Wrong_DataContext_When_Removing()
        {
            // Test for issue #2823
            var canvas = new Canvas();
            var (target, host) = CreateTarget();
            var viewModel = new TestViewModel { Content = "foo" };
            var dataContexts = new List<object?>();

            target.Bind(ContentPresenter.ContentProperty, (IBinding)new TemplateBinding(ContentControl.ContentProperty));
            canvas.GetObservable(ContentPresenter.DataContextProperty).Subscribe(x => dataContexts.Add(x));

            host.DataTemplates.Add(new FuncDataTemplate<string>((_, __) => canvas));
            host.Bind(ContentControl.ContentProperty, new Binding(nameof(TestViewModel.Content)));
            host.DataContext = viewModel;

            Assert.Same(canvas, target.Child);

            viewModel.Content = 42;

            Assert.Equal(new object?[]
            {
                null,
                "foo",
                null,
            }, dataContexts);
        }

        [Fact]
        public void Should_Set_InheritanceParent_Even_When_LogicalParent_Is_Already_Set()
        {
            var logicalParent = new Canvas();
            var child = new TextBlock();
            var (target, host) = CreateTarget();

            ((ISetLogicalParent)child).SetParent(logicalParent);
            target.Content = child;

            Assert.Same(logicalParent, child.Parent);

            // InheritanceParent is exposed via StylingParent.
            Assert.Same(target, ((IStyleHost)child).StylingParent);
        }

        [Fact]
        public void Should_Reset_InheritanceParent_When_Child_Removed()
        {
            var logicalParent = new Canvas();
            var child = new TextBlock();
            var (target, _) = CreateTarget();

            ((ISetLogicalParent)child).SetParent(logicalParent);
            target.Content = child;
            target.Content = null;

            // InheritanceParent is exposed via StylingParent.
            Assert.Same(logicalParent, ((IStyleHost)child).StylingParent);
        }

        [Fact]
        public void Should_Clear_Host_When_Host_Template_Cleared()
        {
            var (target, host) = CreateTarget();

            Assert.Same(host, target.Host);

            host.Template = null;
            host.ApplyTemplate();

            Assert.Null(target.Host);
        }

        [Fact]
        public void Content_Should_Become_DataContext_When_ControlTemplate_Is_Not_Null()
        {
            var (target, _) = CreateTarget();

            var textBlock = new TextBlock
            {
                [!TextBlock.TextProperty] = new Binding("Name"),
            };

            var canvas = new Canvas()
            {
                Name = "Canvas"
            };

            target.ContentTemplate = new FuncDataTemplate<Canvas>((_, __) => textBlock);
            target.Content = canvas;

            Assert.NotNull(target.DataContext);
            Assert.Equal(canvas, target.DataContext);
            Assert.Equal("Canvas", textBlock.Text);
        }

        static (ContentPresenter presenter, ContentControl templatedParent) CreateTarget()
        {
            var templatedParent = new ContentControl
            {
                Template = new FuncControlTemplate<ContentControl>((_, s) => 
                    new ContentPresenter
                    {
                        Name = "PART_ContentPresenter",
                    }.RegisterInNameScope(s)),
            };
            var root = new TestRoot { Child = templatedParent };

            templatedParent.ApplyTemplate();

            return (templatedParent.Presenter!, templatedParent);
        }

        private class TestContentControl : ContentControl, IContentPresenterHost
        {
            public Control? Child { get; set; }
        }

        private class TestViewModel : INotifyPropertyChanged
        {
            private object? _content;

            public object? Content
            {
                get => _content;
                set
                {
                    if (_content != value)
                    {
                        _content = value;
                        PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(nameof(Content)));
                    }
                }
            }

            public event PropertyChangedEventHandler? PropertyChanged;
        }
    }
}