From a8b7e879387a1d83cd724877195c27ac3e320be3 Mon Sep 17 00:00:00 2001 From: Steven Kirk Date: Sun, 12 Jul 2020 15:22:00 +0200 Subject: [PATCH] Added IRecyclingDataTemplate. In #4218 we imported `IElementFactory` from WinUI which is broadly analogous to a recycling datatemplate for lists. In Avalonia this implement `IDataTemplate` in order to have a common base class for all types of data templates. The problem with this is that `IDataTemplate` already had a `SupportsRecycling` property which is incompatible with the way recycling is implemented in `IElementFactory`. Instead, introduce an `IRecyclingDataTemplate` to signal data templates that support recycling. --- .../Generators/TreeItemContainerGenerator.cs | 1 - .../Presenters/ContentPresenter.cs | 21 +++++++------- .../Repeater/ElementFactory.cs | 2 -- .../Repeater/ItemTemplateWrapper.cs | 1 - .../Templates/FuncDataTemplate.cs | 29 ++++++++++++++----- .../Templates/FuncTemplate`2.cs | 6 ++-- .../Templates/IDataTemplate.cs | 12 ++++---- .../Templates/IRecyclingDataTemplate.cs | 25 ++++++++++++++++ .../Diagnostics/ViewLocator.cs | 2 -- .../Templates/DataTemplate.cs | 11 ++++--- .../Templates/TreeDataTemplate.cs | 2 -- .../TreeViewTests.cs | 2 -- 12 files changed, 71 insertions(+), 43 deletions(-) create mode 100644 src/Avalonia.Controls/Templates/IRecyclingDataTemplate.cs diff --git a/src/Avalonia.Controls/Generators/TreeItemContainerGenerator.cs b/src/Avalonia.Controls/Generators/TreeItemContainerGenerator.cs index cd1ce3deae..9e65ef5f81 100644 --- a/src/Avalonia.Controls/Generators/TreeItemContainerGenerator.cs +++ b/src/Avalonia.Controls/Generators/TreeItemContainerGenerator.cs @@ -142,7 +142,6 @@ namespace Avalonia.Controls.Generators private readonly IDataTemplate _inner; public WrapperTreeDataTemplate(IDataTemplate inner) => _inner = inner; public IControl Build(object param) => _inner.Build(param); - public bool SupportsRecycling => _inner.SupportsRecycling; public bool Match(object data) => _inner.Match(data); public InstancedBinding ItemsSelector(object item) => null; } diff --git a/src/Avalonia.Controls/Presenters/ContentPresenter.cs b/src/Avalonia.Controls/Presenters/ContentPresenter.cs index c4571505ba..8837901816 100644 --- a/src/Avalonia.Controls/Presenters/ContentPresenter.cs +++ b/src/Avalonia.Controls/Presenters/ContentPresenter.cs @@ -86,7 +86,7 @@ namespace Avalonia.Controls.Presenters private IControl _child; private bool _createdChild; - private IDataTemplate _dataTemplate; + private IRecyclingDataTemplate _recyclingDataTemplate; private readonly BorderRenderHelper _borderRenderer = new BorderRenderHelper(); /// @@ -281,7 +281,7 @@ namespace Avalonia.Controls.Presenters protected override void OnAttachedToLogicalTree(LogicalTreeAttachmentEventArgs e) { base.OnAttachedToLogicalTree(e); - _dataTemplate = null; + _recyclingDataTemplate = null; _createdChild = false; InvalidateMeasure(); } @@ -307,22 +307,21 @@ namespace Avalonia.Controls.Presenters { var dataTemplate = this.FindDataTemplate(content, ContentTemplate) ?? FuncDataTemplate.Default; - // We have content and it isn't a control, so if the new data template is the same - // as the old data template, try to recycle the existing child control to display - // the new data. - if (dataTemplate == _dataTemplate && dataTemplate.SupportsRecycling) + if (dataTemplate is IRecyclingDataTemplate rdt) { - newChild = oldChild; + var toRecycle = rdt == _recyclingDataTemplate ? oldChild : null; + newChild = rdt.Build(content, toRecycle); + _recyclingDataTemplate = rdt; } else { - _dataTemplate = dataTemplate; - newChild = _dataTemplate.Build(content); + newChild = dataTemplate.Build(content); + _recyclingDataTemplate = null; } } else { - _dataTemplate = null; + _recyclingDataTemplate = null; } return newChild; @@ -422,7 +421,7 @@ namespace Avalonia.Controls.Presenters LogicalChildren.Remove(Child); ((ISetInheritanceParent)Child).SetParent(Child.Parent); Child = null; - _dataTemplate = null; + _recyclingDataTemplate = null; } InvalidateMeasure(); diff --git a/src/Avalonia.Controls/Repeater/ElementFactory.cs b/src/Avalonia.Controls/Repeater/ElementFactory.cs index 1c1b71af88..644e077221 100644 --- a/src/Avalonia.Controls/Repeater/ElementFactory.cs +++ b/src/Avalonia.Controls/Repeater/ElementFactory.cs @@ -4,8 +4,6 @@ namespace Avalonia.Controls { public abstract class ElementFactory : IElementFactory { - bool IDataTemplate.SupportsRecycling => false; - public IControl Build(object data) { return GetElementCore(new ElementFactoryGetArgs { Data = data }); diff --git a/src/Avalonia.Controls/Repeater/ItemTemplateWrapper.cs b/src/Avalonia.Controls/Repeater/ItemTemplateWrapper.cs index 4b784375a9..dd97cde218 100644 --- a/src/Avalonia.Controls/Repeater/ItemTemplateWrapper.cs +++ b/src/Avalonia.Controls/Repeater/ItemTemplateWrapper.cs @@ -13,7 +13,6 @@ namespace Avalonia.Controls public ItemTemplateWrapper(IDataTemplate dataTemplate) => _dataTemplate = dataTemplate; - public bool SupportsRecycling => false; public IControl Build(object param) => GetElement(null, param); public bool Match(object data) => _dataTemplate.Match(data); diff --git a/src/Avalonia.Controls/Templates/FuncDataTemplate.cs b/src/Avalonia.Controls/Templates/FuncDataTemplate.cs index d454a29021..1afd86a11e 100644 --- a/src/Avalonia.Controls/Templates/FuncDataTemplate.cs +++ b/src/Avalonia.Controls/Templates/FuncDataTemplate.cs @@ -6,7 +6,7 @@ namespace Avalonia.Controls.Templates /// /// Builds a control for a piece of data. /// - public class FuncDataTemplate : FuncTemplate, IDataTemplate + public class FuncDataTemplate : FuncTemplate, IRecyclingDataTemplate { /// /// The default data template used in the case where no matching data template is found. @@ -30,10 +30,8 @@ namespace Avalonia.Controls.Templates }, true); - /// - /// The implementation of the method. - /// private readonly Func _match; + private readonly bool _supportsRecycling; /// /// Initializes a new instance of the class. @@ -70,12 +68,9 @@ namespace Avalonia.Controls.Templates Contract.Requires(match != null); _match = match; - SupportsRecycling = supportsRecycling; + _supportsRecycling = supportsRecycling; } - /// - public bool SupportsRecycling { get; } - /// /// Checks to see if this data template matches the specified data. /// @@ -88,6 +83,24 @@ namespace Avalonia.Controls.Templates return _match(data); } + /// + /// Creates or recycles a control to display the specified data. + /// + /// The data to display. + /// An optional control to recycle. + /// + /// The control if supplied and applicable to + /// , otherwise a new control. + /// + /// + /// The caller should ensure that any control passed to + /// originated from the same data template. + /// + public IControl Build(object data, IControl existing) + { + return _supportsRecycling && existing is object ? existing : Build(data); + } + /// /// Determines of an object is of the specified type. /// diff --git a/src/Avalonia.Controls/Templates/FuncTemplate`2.cs b/src/Avalonia.Controls/Templates/FuncTemplate`2.cs index d08616b968..cd0e3ad603 100644 --- a/src/Avalonia.Controls/Templates/FuncTemplate`2.cs +++ b/src/Avalonia.Controls/Templates/FuncTemplate`2.cs @@ -1,5 +1,7 @@ using System; +#nullable enable + namespace Avalonia.Controls.Templates { /// @@ -18,9 +20,7 @@ namespace Avalonia.Controls.Templates /// The function used to create the control. public FuncTemplate(Func func) { - Contract.Requires(func != null); - - _func = func; + _func = func ?? throw new ArgumentNullException(nameof(func)); } /// diff --git a/src/Avalonia.Controls/Templates/IDataTemplate.cs b/src/Avalonia.Controls/Templates/IDataTemplate.cs index cfde029eb8..0368748a0b 100644 --- a/src/Avalonia.Controls/Templates/IDataTemplate.cs +++ b/src/Avalonia.Controls/Templates/IDataTemplate.cs @@ -1,3 +1,7 @@ +using System; + +#nullable enable + namespace Avalonia.Controls.Templates { /// @@ -5,12 +9,6 @@ namespace Avalonia.Controls.Templates /// public interface IDataTemplate : ITemplate { - /// - /// Gets a value indicating whether the data template supports recycling of the generated - /// control. - /// - bool SupportsRecycling { get; } - /// /// Checks to see if this data template matches the specified data. /// @@ -20,4 +18,4 @@ namespace Avalonia.Controls.Templates /// bool Match(object data); } -} \ No newline at end of file +} diff --git a/src/Avalonia.Controls/Templates/IRecyclingDataTemplate.cs b/src/Avalonia.Controls/Templates/IRecyclingDataTemplate.cs new file mode 100644 index 0000000000..25956a9c9a --- /dev/null +++ b/src/Avalonia.Controls/Templates/IRecyclingDataTemplate.cs @@ -0,0 +1,25 @@ +#nullable enable + +namespace Avalonia.Controls.Templates +{ + /// + /// An that supports recycling existing elements. + /// + public interface IRecyclingDataTemplate : IDataTemplate + { + /// + /// Creates or recycles a control to display the specified data. + /// + /// The data to display. + /// An optional control to recycle. + /// + /// The control if supplied and applicable to + /// , otherwise a new control. + /// + /// + /// The caller should ensure that any control passed to + /// originated from the same data template. + /// + IControl Build(object data, IControl? existing); + } +} diff --git a/src/Avalonia.Diagnostics/Diagnostics/ViewLocator.cs b/src/Avalonia.Diagnostics/Diagnostics/ViewLocator.cs index c06fbec801..be3564e781 100644 --- a/src/Avalonia.Diagnostics/Diagnostics/ViewLocator.cs +++ b/src/Avalonia.Diagnostics/Diagnostics/ViewLocator.cs @@ -7,8 +7,6 @@ namespace Avalonia.Diagnostics { internal class ViewLocator : IDataTemplate { - public bool SupportsRecycling => false; - public IControl Build(object data) { var name = data.GetType().FullName.Replace("ViewModel", "View"); diff --git a/src/Markup/Avalonia.Markup.Xaml/Templates/DataTemplate.cs b/src/Markup/Avalonia.Markup.Xaml/Templates/DataTemplate.cs index 5663d08412..07c5451135 100644 --- a/src/Markup/Avalonia.Markup.Xaml/Templates/DataTemplate.cs +++ b/src/Markup/Avalonia.Markup.Xaml/Templates/DataTemplate.cs @@ -5,7 +5,7 @@ using Avalonia.Metadata; namespace Avalonia.Markup.Xaml.Templates { - public class DataTemplate : IDataTemplate + public class DataTemplate : IRecyclingDataTemplate { public Type DataType { get; set; } @@ -14,8 +14,6 @@ namespace Avalonia.Markup.Xaml.Templates [TemplateContent] public object Content { get; set; } - public bool SupportsRecycling { get; set; } = true; - public bool Match(object data) { if (DataType == null) @@ -28,6 +26,11 @@ namespace Avalonia.Markup.Xaml.Templates } } - public IControl Build(object data) => TemplateContent.Load(Content).Control; + public IControl Build(object data) => Build(data, null); + + public IControl Build(object data, IControl existing) + { + return existing ?? TemplateContent.Load(Content).Control; + } } } diff --git a/src/Markup/Avalonia.Markup.Xaml/Templates/TreeDataTemplate.cs b/src/Markup/Avalonia.Markup.Xaml/Templates/TreeDataTemplate.cs index b96486235a..b8e1c2df80 100644 --- a/src/Markup/Avalonia.Markup.Xaml/Templates/TreeDataTemplate.cs +++ b/src/Markup/Avalonia.Markup.Xaml/Templates/TreeDataTemplate.cs @@ -18,8 +18,6 @@ namespace Avalonia.Markup.Xaml.Templates [AssignBinding] public Binding ItemsSource { get; set; } - public bool SupportsRecycling { get; set; } = true; - public bool Match(object data) { if (DataType == null) diff --git a/tests/Avalonia.Controls.UnitTests/TreeViewTests.cs b/tests/Avalonia.Controls.UnitTests/TreeViewTests.cs index c1bd45bcad..c25ad19027 100644 --- a/tests/Avalonia.Controls.UnitTests/TreeViewTests.cs +++ b/tests/Avalonia.Controls.UnitTests/TreeViewTests.cs @@ -1273,8 +1273,6 @@ namespace Avalonia.Controls.UnitTests return new TextBlock { Text = node.Value }; } - public bool SupportsRecycling => false; - public InstancedBinding ItemsSelector(object item) { var obs = ExpressionObserver.Create(item, o => (o as Node).Children);