diff --git a/src/Avalonia.Base/Styling/ChildSelector.cs b/src/Avalonia.Base/Styling/ChildSelector.cs index 5c92182b80..8675ca8820 100644 --- a/src/Avalonia.Base/Styling/ChildSelector.cs +++ b/src/Avalonia.Base/Styling/ChildSelector.cs @@ -37,13 +37,13 @@ namespace Avalonia.Styling return _selectorString; } - protected override SelectorMatch Evaluate(IStyleable control, bool subscribe) + protected override SelectorMatch Evaluate(IStyleable control, IStyle? parent, bool subscribe) { var controlParent = ((ILogical)control).LogicalParent; if (controlParent != null) { - var parentMatch = _parent.Match((IStyleable)controlParent, subscribe); + var parentMatch = _parent.Match((IStyleable)controlParent, parent, subscribe); if (parentMatch.Result == SelectorMatchResult.Sometimes) { diff --git a/src/Avalonia.Base/Styling/DescendentSelector.cs b/src/Avalonia.Base/Styling/DescendentSelector.cs index dde88b3436..b164ad1c69 100644 --- a/src/Avalonia.Base/Styling/DescendentSelector.cs +++ b/src/Avalonia.Base/Styling/DescendentSelector.cs @@ -35,7 +35,7 @@ namespace Avalonia.Styling return _selectorString; } - protected override SelectorMatch Evaluate(IStyleable control, bool subscribe) + protected override SelectorMatch Evaluate(IStyleable control, IStyle? parent, bool subscribe) { var c = (ILogical)control; var descendantMatches = new OrActivatorBuilder(); @@ -46,7 +46,7 @@ namespace Avalonia.Styling if (c is IStyleable) { - var match = _parent.Match((IStyleable)c, subscribe); + var match = _parent.Match((IStyleable)c, parent, subscribe); if (match.Result == SelectorMatchResult.Sometimes) { diff --git a/src/Avalonia.Base/Styling/NestingSelector.cs b/src/Avalonia.Base/Styling/NestingSelector.cs new file mode 100644 index 0000000000..1be54dea3c --- /dev/null +++ b/src/Avalonia.Base/Styling/NestingSelector.cs @@ -0,0 +1,29 @@ +using System; + +namespace Avalonia.Styling +{ + /// + /// The `&` nesting style selector. + /// + internal class NestingSelector : Selector + { + public override bool InTemplate => false; + public override bool IsCombinator => false; + public override Type? TargetType => null; + + public override string ToString() => "&"; + + protected override SelectorMatch Evaluate(IStyleable control, IStyle? parent, bool subscribe) + { + if (parent is Style s && s.Selector is Selector selector) + { + return selector.Match(control, null, subscribe); + } + + throw new InvalidOperationException( + "Nesting selector was specified but cannot determine parent selector."); + } + + protected override Selector? MovePrevious() => null; + } +} diff --git a/src/Avalonia.Base/Styling/NotSelector.cs b/src/Avalonia.Base/Styling/NotSelector.cs index ab4e9d5d7f..c4beca6b9e 100644 --- a/src/Avalonia.Base/Styling/NotSelector.cs +++ b/src/Avalonia.Base/Styling/NotSelector.cs @@ -45,9 +45,9 @@ namespace Avalonia.Styling return _selectorString; } - protected override SelectorMatch Evaluate(IStyleable control, bool subscribe) + protected override SelectorMatch Evaluate(IStyleable control, IStyle? parent, bool subscribe) { - var innerResult = _argument.Match(control, subscribe); + var innerResult = _argument.Match(control, parent, subscribe); switch (innerResult.Result) { diff --git a/src/Avalonia.Base/Styling/NthChildSelector.cs b/src/Avalonia.Base/Styling/NthChildSelector.cs index aff34ea17c..cbb5e64772 100644 --- a/src/Avalonia.Base/Styling/NthChildSelector.cs +++ b/src/Avalonia.Base/Styling/NthChildSelector.cs @@ -48,7 +48,7 @@ namespace Avalonia.Styling public int Step { get; } public int Offset { get; } - protected override SelectorMatch Evaluate(IStyleable control, bool subscribe) + protected override SelectorMatch Evaluate(IStyleable control, IStyle? parent, bool subscribe) { if (!(control is ILogical logical)) { diff --git a/src/Avalonia.Base/Styling/OrSelector.cs b/src/Avalonia.Base/Styling/OrSelector.cs index 3d6db9b01e..a34712caaf 100644 --- a/src/Avalonia.Base/Styling/OrSelector.cs +++ b/src/Avalonia.Base/Styling/OrSelector.cs @@ -65,14 +65,14 @@ namespace Avalonia.Styling return _selectorString; } - protected override SelectorMatch Evaluate(IStyleable control, bool subscribe) + protected override SelectorMatch Evaluate(IStyleable control, IStyle? parent, bool subscribe) { var activators = new OrActivatorBuilder(); var neverThisInstance = false; foreach (var selector in _selectors) { - var match = selector.Match(control, subscribe); + var match = selector.Match(control, parent, subscribe); switch (match.Result) { diff --git a/src/Avalonia.Base/Styling/PropertyEqualsSelector.cs b/src/Avalonia.Base/Styling/PropertyEqualsSelector.cs index 1cd1a650ef..34474fb7ab 100644 --- a/src/Avalonia.Base/Styling/PropertyEqualsSelector.cs +++ b/src/Avalonia.Base/Styling/PropertyEqualsSelector.cs @@ -74,7 +74,7 @@ namespace Avalonia.Styling } /// - protected override SelectorMatch Evaluate(IStyleable control, bool subscribe) + protected override SelectorMatch Evaluate(IStyleable control, IStyle? parent, bool subscribe) { if (subscribe) { diff --git a/src/Avalonia.Base/Styling/Selector.cs b/src/Avalonia.Base/Styling/Selector.cs index 0740e0f891..008ce7f3a5 100644 --- a/src/Avalonia.Base/Styling/Selector.cs +++ b/src/Avalonia.Base/Styling/Selector.cs @@ -33,22 +33,25 @@ namespace Avalonia.Styling /// Tries to match the selector with a control. /// /// The control. + /// + /// The parent style, if the style containing the selector is a nested style. + /// /// /// Whether the match should subscribe to changes in order to track the match over time, /// or simply return an immediate result. /// /// A . - public SelectorMatch Match(IStyleable control, bool subscribe = true) + public SelectorMatch Match(IStyleable control, IStyle? parent = null, bool subscribe = true) { // First match the selector until a combinator is found. Selectors are stored from // right-to-left, so MatchUntilCombinator reverses this order because the type selector // will be on the left. - var match = MatchUntilCombinator(control, this, subscribe, out var combinator); + var match = MatchUntilCombinator(control, this, parent, subscribe, out var combinator); // If the pre-combinator selector matches, we can now match the combinator, if any. if (match.IsMatch && combinator is object) { - match = match.And(combinator.Match(control, subscribe)); + match = match.And(combinator.Match(control, parent, subscribe)); // If we have a combinator then we can never say that we always match a control of // this type, because by definition the combinator matches on things outside of the @@ -68,12 +71,15 @@ namespace Avalonia.Styling /// Evaluates the selector for a match. /// /// The control. + /// + /// The parent style, if the style containing the selector is a nested style. + /// /// /// Whether the match should subscribe to changes in order to track the match over time, /// or simply return an immediate result. /// /// A . - protected abstract SelectorMatch Evaluate(IStyleable control, bool subscribe); + protected abstract SelectorMatch Evaluate(IStyleable control, IStyle? parent, bool subscribe); /// /// Moves to the previous selector. @@ -83,13 +89,18 @@ namespace Avalonia.Styling private static SelectorMatch MatchUntilCombinator( IStyleable control, Selector start, + IStyle? parent, bool subscribe, out Selector? combinator) { combinator = null; var activators = new AndActivatorBuilder(); - var result = Match(control, start, subscribe, ref activators, ref combinator); + var foundNested = false; + var result = Match(control, start, parent, subscribe, ref activators, ref combinator, ref foundNested); + + if (parent is not null && !foundNested) + throw new InvalidOperationException("Nesting selector '&' must appear in child selector."); return result == SelectorMatchResult.Sometimes ? new SelectorMatch(activators.Get()) : @@ -99,9 +110,11 @@ namespace Avalonia.Styling private static SelectorMatchResult Match( IStyleable control, Selector selector, + IStyle? parent, bool subscribe, ref AndActivatorBuilder activators, - ref Selector? combinator) + ref Selector? combinator, + ref bool foundNested) { var previous = selector.MovePrevious(); @@ -110,7 +123,7 @@ namespace Avalonia.Styling // opportunity to exit early. if (previous != null && !previous.IsCombinator) { - var previousMatch = Match(control, previous, subscribe, ref activators, ref combinator); + var previousMatch = Match(control, previous, parent, subscribe, ref activators, ref combinator, ref foundNested); if (previousMatch < SelectorMatchResult.Sometimes) { @@ -118,8 +131,10 @@ namespace Avalonia.Styling } } + foundNested |= selector is NestingSelector; + // Match this selector. - var match = selector.Evaluate(control, subscribe); + var match = selector.Evaluate(control, parent, subscribe); if (!match.IsMatch) { diff --git a/src/Avalonia.Base/Styling/Selectors.cs b/src/Avalonia.Base/Styling/Selectors.cs index 7c66469cf1..a036c140c2 100644 --- a/src/Avalonia.Base/Styling/Selectors.cs +++ b/src/Avalonia.Base/Styling/Selectors.cs @@ -109,6 +109,15 @@ namespace Avalonia.Styling } } + public static Selector Nesting(this Selector? previous) + { + if (previous is not null) + throw new InvalidOperationException( + "Nesting selector '&' must appear at the start of the style selector."); + + return new NestingSelector(); + } + /// /// Returns a selector which inverts the results of selector argument. /// diff --git a/src/Avalonia.Base/Styling/Style.cs b/src/Avalonia.Base/Styling/Style.cs index 00819ef7be..a3a7ea29d3 100644 --- a/src/Avalonia.Base/Styling/Style.cs +++ b/src/Avalonia.Base/Styling/Style.cs @@ -4,8 +4,6 @@ using Avalonia.Animation; using Avalonia.Controls; using Avalonia.Metadata; -#nullable enable - namespace Avalonia.Styling { /// @@ -14,6 +12,7 @@ namespace Avalonia.Styling public class Style : AvaloniaObject, IStyle, IResourceProvider { private IResourceHost? _owner; + private StyleChildren? _children; private IResourceDictionary? _resources; private List? _setters; private List? _animations; @@ -34,6 +33,14 @@ namespace Avalonia.Styling Selector = selector(null); } + /// + /// Gets the children of the style. + /// + public IList Children => _children ??= new(this); + + /// + /// Gets the or Application that hosts the style. + /// public IResourceHost? Owner { get => _owner; @@ -47,6 +54,11 @@ namespace Avalonia.Styling } } + /// + /// Gets the parent style if this style is hosted in a collection. + /// + public Style? Parent { get; private set; } + /// /// Gets or sets a dictionary of style resources. /// @@ -90,7 +102,7 @@ namespace Avalonia.Styling public IList Animations => _animations ??= new List(); bool IResourceNode.HasResources => _resources?.Count > 0; - IReadOnlyList IStyle.Children => Array.Empty(); + IReadOnlyList IStyle.Children => (IReadOnlyList?)_children ?? Array.Empty(); public event EventHandler? OwnerChanged; @@ -98,7 +110,7 @@ namespace Avalonia.Styling { target = target ?? throw new ArgumentNullException(nameof(target)); - var match = Selector is object ? Selector.Match(target) : + var match = Selector is object ? Selector.Match(target, Parent) : target == host ? SelectorMatch.AlwaysThisInstance : SelectorMatch.NeverThisInstance; if (match.IsMatch && (_setters is object || _animations is object)) @@ -156,5 +168,7 @@ namespace Avalonia.Styling _resources?.RemoveOwner(owner); } } + + internal void SetParent(Style? parent) => Parent = parent; } } diff --git a/src/Avalonia.Base/Styling/StyleChildren.cs b/src/Avalonia.Base/Styling/StyleChildren.cs new file mode 100644 index 0000000000..21ac3c4072 --- /dev/null +++ b/src/Avalonia.Base/Styling/StyleChildren.cs @@ -0,0 +1,29 @@ +using System.Collections.ObjectModel; + +namespace Avalonia.Styling +{ + internal class StyleChildren : Collection + { + private readonly Style _owner; + + public StyleChildren(Style owner) => _owner = owner; + + protected override void InsertItem(int index, IStyle item) + { + base.InsertItem(index, item); + (item as Style)?.SetParent(_owner); + } + + protected override void RemoveItem(int index) + { + (Items[index] as Style)?.SetParent(null); + base.RemoveItem(index); + } + + protected override void SetItem(int index, IStyle item) + { + base.SetItem(index, item); + (item as Style)?.SetParent(_owner); + } + } +} diff --git a/src/Avalonia.Base/Styling/TemplateSelector.cs b/src/Avalonia.Base/Styling/TemplateSelector.cs index e8051efa6d..6f0f9e0900 100644 --- a/src/Avalonia.Base/Styling/TemplateSelector.cs +++ b/src/Avalonia.Base/Styling/TemplateSelector.cs @@ -36,7 +36,7 @@ namespace Avalonia.Styling return _selectorString; } - protected override SelectorMatch Evaluate(IStyleable control, bool subscribe) + protected override SelectorMatch Evaluate(IStyleable control, IStyle? parent, bool subscribe) { var templatedParent = control.TemplatedParent as IStyleable; @@ -45,7 +45,7 @@ namespace Avalonia.Styling return SelectorMatch.NeverThisInstance; } - return _parent.Match(templatedParent, subscribe); + return _parent.Match(templatedParent, parent, subscribe); } protected override Selector? MovePrevious() => null; diff --git a/src/Avalonia.Base/Styling/TypeNameAndClassSelector.cs b/src/Avalonia.Base/Styling/TypeNameAndClassSelector.cs index ef48c4a8cd..ae9b14635f 100644 --- a/src/Avalonia.Base/Styling/TypeNameAndClassSelector.cs +++ b/src/Avalonia.Base/Styling/TypeNameAndClassSelector.cs @@ -94,7 +94,7 @@ namespace Avalonia.Styling } /// - protected override SelectorMatch Evaluate(IStyleable control, bool subscribe) + protected override SelectorMatch Evaluate(IStyleable control, IStyle? parent, bool subscribe) { if (TargetType != null) { diff --git a/tests/Avalonia.Base.UnitTests/Styling/SelectorTests_Nesting.cs b/tests/Avalonia.Base.UnitTests/Styling/SelectorTests_Nesting.cs new file mode 100644 index 0000000000..cee7e748ba --- /dev/null +++ b/tests/Avalonia.Base.UnitTests/Styling/SelectorTests_Nesting.cs @@ -0,0 +1,132 @@ +using System; +using Avalonia.Controls; +using Avalonia.Styling; +using Avalonia.Styling.Activators; +using Xunit; + +namespace Avalonia.Base.UnitTests.Styling +{ + public class SelectorTests_Nesting + { + [Fact] + public void Parent_Selector_Doesnt_Match_OfType() + { + var control = new Control2(); + Style nested; + var parent = new Style(x => x.OfType()) + { + Children = + { + (nested = new Style(x => x.Nesting().Class("foo"))), + } + }; + + var match = nested.Selector.Match(control, parent); + Assert.Equal(SelectorMatchResult.NeverThisType, match.Result); + } + + [Fact] + public void Nested_Class_Selector() + { + var control = new Control1 { Classes = { "foo" } }; + Style nested; + var parent = new Style(x => x.OfType()) + { + Children = + { + (nested = new Style(x => x.Nesting().Class("foo"))), + } + }; + + var match = nested.Selector.Match(control, parent); + Assert.Equal(SelectorMatchResult.Sometimes, match.Result); + + var sink = new ActivatorSink(match.Activator); + + Assert.True(sink.Active); + control.Classes.Clear(); + Assert.False(sink.Active); + } + + [Fact] + public void Nesting_With_No_Parent_Style_Fails() + { + var control = new Control1(); + var style = new Style(x => x.Nesting().OfType()); + + Assert.Throws(() => style.Selector.Match(control, null)); + } + + [Fact] + public void Nesting_With_No_Parent_Selector_Fails() + { + var control = new Control1(); + Style nested; + var parent = new Style + { + Children = + { + (nested = new Style(x => x.Nesting().Class("foo"))), + } + }; + + Assert.Throws(() => nested.Selector.Match(control, parent)); + } + + [Fact] + public void Nesting_Must_Appear_At_Start_Of_Selector() + { + var control = new Control1(); + Assert.Throws(() => new Style(x => x.OfType().Nesting())); + } + + [Fact] + public void Nesting_Must_Appear() + { + var control = new Control1(); + Style nested; + var parent = new Style + { + Children = + { + (nested = new Style(x => x.OfType().Class("foo"))), + } + }; + + Assert.Throws(() => nested.Selector.Match(control, parent)); + } + + [Fact] + public void Nesting_Must_Appear_In_All_Or_Arguments() + { + var control = new Control1(); + Style nested; + var parent = new Style(x => x.OfType()) + { + Children = + { + (nested = new Style(x => Selectors.Or( + x.Nesting().Class("foo"), + x.Class("bar")))) + } + }; + + Assert.Throws(() => nested.Selector.Match(control, parent)); + } + + public class Control1 : Control + { + } + + public class Control2 : Control + { + } + + private class ActivatorSink : IStyleActivatorSink + { + public ActivatorSink(IStyleActivator source) => source.Subscribe(this); + public bool Active { get; private set; } + public void OnNext(bool value, int tag) => Active = value; + } + } +}