MultiViewZero levelled up.

FunctionZero.Maui.Controls/Controls/MultiView/MultiViewAnimation.cs

@@ -24,11 +24,12 @@ private static object MakeDud(BindableObject bindable)
 
         #region FromProperty
 
-        public static readonly BindableProperty FromProperty = BindableProperty.Create(nameof(From), typeof(double), typeof(MultiViewAnimation), 0.0, BindingMode.OneWay, null, FromChanged);
+        public static readonly BindableProperty FromProperty = BindableProperty.Create(nameof(From), typeof(ExpressionTree), typeof(MultiViewAnimation), _dudExpression, BindingMode.OneWay, null, FromChanged, null, null, MakeDud);
 
-        public double From
+        [TypeConverter(typeof(ExpressionTreeTypeConverter))]
+        public ExpressionTree From
         {
-            get { return (double)GetValue(FromProperty); }
+            get { return (ExpressionTree)GetValue(FromProperty); }
             set { SetValue(FromProperty, value); }
         }
 
@@ -42,11 +43,12 @@ private static void FromChanged(BindableObject bindable, object oldValue, object
 
         #region ToViewNameProperty
 
-        public static readonly BindableProperty ToProperty = BindableProperty.Create(nameof(To), typeof(double), typeof(MultiViewAnimation), 0.0, BindingMode.OneWay, null, ToChanged);
+        public static readonly BindableProperty ToProperty = BindableProperty.Create(nameof(To), typeof(ExpressionTree), typeof(MultiViewAnimation), _dudExpression, BindingMode.OneWay, null, ToChanged, null, null, MakeDud);
 
-        public double To
+        [TypeConverter(typeof(ExpressionTreeTypeConverter))]
+        public ExpressionTree To
         {
-            get { return (double)GetValue(ToProperty); }
+            get { return (ExpressionTree)GetValue(ToProperty); }
             set { SetValue(ToProperty, value); }
         }
 

FunctionZero.Maui.Controls/Controls/MultiView/MultiViewZero.cs

@@ -1,5 +1,8 @@
-using FunctionZero.ExpressionParserZero.BackingStore;
+using FunctionZero.ExpressionParserZero;
+using FunctionZero.ExpressionParserZero.BackingStore;
 using FunctionZero.ExpressionParserZero.Evaluator;
+using FunctionZero.ExpressionParserZero.Operands;
+using FunctionZero.ExpressionParserZero.Parser;
 using FunctionZero.Maui.zBind.z;
 using Microsoft.Maui.Layouts;
 using System.ComponentModel;
@@ -11,10 +14,16 @@ namespace FunctionZero.Maui.Controls
     public class MultiViewZero : Layout
     {
         private readonly PocoBackingStore _backingStore;
-        private IView _currentView;
-        private IView _previousView;
+
+        // Every expression acts on 'this' and has a 'View' property that refers to its target.
+        // View will use *magic* to always have the right value for any Animation that is running.
+        // E.g. 'View.Opacity = value' will set the Opacity of the target View to the animation value during the animation.
         public IView View { get; private set; }
 
+        // A *magic* property that is set to the easing-function value for each Animation.
+        // E.g. 'View.Opacity = value' will set the Opacity of the target View to the animation value during the animation.
+        public double value { get; protected set; }
+
         public MultiViewZero()
         {
             InAnimations = new List<MultiViewAnimation>();
@@ -25,19 +34,11 @@ public MultiViewZero()
 
         private void MultiViewZero_Loaded(object sender, EventArgs e)
         {
-            var oldCurrentView = _currentView;
+            // Once only ever.
+            this.Loaded -= MultiViewZero_Loaded;
 
-            if (oldCurrentView != null)
-            {
-                Debug.WriteLine("Got you!");
-            }
             foreach (IView item in this)
-            {
-                // Temporarily set _currentView so expressions can reference 'View' e.g. View.IsVisible=...
-                _currentView = item;
-                TryEvaluate(CreatedExpression, _backingStore, true);
-            }
-            _currentView = oldCurrentView;
+                TryEvaluate(CreatedExpression, _backingStore, item);
         }
 
         protected override ILayoutManager CreateLayoutManager()
@@ -149,98 +150,123 @@ private static void TopViewNameChanged(BindableObject bindable, object oldValue,
             if (flag == false)
                 self.SetTopView(null);
         }
+        View _topView;
 
         private void SetTopView(View theChildView)
         {
-            if (_previousView is View outgoingPreviousViewAsView)
-            {
-                if (outgoingPreviousViewAsView.AnimationIsRunning("PreviousAnimation"))
-                {
-                    outgoingPreviousViewAsView.AbortAnimation("PreviousAnimation");
+            if (_topView == theChildView)
+                return;
 
-                    foreach (var anim in OutAnimations)
-                        TryEvaluate(anim.FinishedExpression, _backingStore, false);
-                }
-            }
-            if (_currentView is View outgoingCurrentViewAsView)
+            // If there is something to animate out ...
+            if (_topView != null)
             {
-                if (outgoingCurrentViewAsView.AnimationIsRunning("CurrentAnimation"))
+                if (_topView.IsLoaded)
                 {
-                    outgoingCurrentViewAsView.AbortAnimation("CurrentAnimation");
-
-                    foreach (var anim in InAnimations)
-                        TryEvaluate(anim.FinishedExpression, _backingStore, true);
-                }
-            }
+                    // If there's an old animation it'll be on its way in. Kill it.
+                    if (_topView.AnimationIsRunning("TheAnimation"))
+                    {
+                        _topView.AbortAnimation("TheAnimation");
 
-            _previousView = _currentView;
-            _currentView = theChildView;
+                        foreach (var anim in InAnimations)
+                            TryEvaluate(anim.FinishedExpression, _backingStore, _topView);
+                    }
 
-            if (_previousView is View previousViewAsView)
-            {
-                // Workaround for https://github.com/dotnet/maui/issues/18433
-                if (previousViewAsView.IsLoaded)
-                {
                     var a = new Animation();
 
-                    foreach (MultiViewAnimation anim in OutAnimations)
-                    {
-                        TryEvaluate(anim.StartingExpression, _backingStore, false);
+                    var localTopView = _topView;
 
-                        a.Add(0, 1, new Animation(val => { value = val; TryEvaluate(anim.Expression, _backingStore, false); }, anim.From, anim.To, anim.EasingFunc, () => TryEvaluate(anim.FinishedExpression, _backingStore, false)));
+                    // Animate the old topview out ...
+                    foreach (var anim in OutAnimations)
+                    {
+                        TryEvaluate(anim.StartingExpression, _backingStore, _topView);
+                        a.Add(0, 1, new Animation(val => { value = val; View = localTopView; TryEvaluate(anim.Expression, _backingStore, localTopView); }, EvaluateDouble(anim.From, _backingStore, localTopView), EvaluateDouble(anim.To, _backingStore, localTopView), anim.EasingFunc, () => TryEvaluate(anim.FinishedExpression, _backingStore, localTopView)));
                     }
-                    a.Commit(previousViewAsView, "PreviousAnimation", 16, OutDuration, null, null, () => false);
+                    a.Commit(_topView, "TheAnimation", 16, InDuration, null, null, () => false);
                 }
                 else
                 {
                     value = 1.0;
                     foreach (var anim in OutAnimations)
-                        TryEvaluate(anim.Expression, _backingStore, false);
+                        TryEvaluate(anim.Expression, _backingStore, _topView);
                 }
+
             }
-            if (_currentView is View currentViewAsView)
+
+            _topView = theChildView;
+
+            // If there is something to animate in ...
+            if (_topView != null)
             {
-                if (currentViewAsView.IsLoaded)
+                if (_topView.IsLoaded)
                 {
+                    // If there's an old animation it'll be on its way out. Kill it.
+                    if (_topView.AnimationIsRunning("TheAnimation"))
+                    {
+                        _topView.AbortAnimation("TheAnimation");
+
+                        foreach (var anim in OutAnimations)
+                            TryEvaluate(anim.FinishedExpression, _backingStore, _topView);
+                    }
+
                     var a = new Animation();
 
+                    var localTopView = _topView;
+
+                    // Animate the old topview out ...
                     foreach (var anim in InAnimations)
                     {
-                        TryEvaluate(anim.StartingExpression, _backingStore, true);
-                        a.Add(0, 1, new Animation(val => { value = val; TryEvaluate(anim.Expression, _backingStore, true); }, anim.From, anim.To, anim.EasingFunc, () => TryEvaluate(anim.FinishedExpression, _backingStore, true)));
+                        TryEvaluate(anim.StartingExpression, _backingStore, localTopView);
+                        a.Add(0, 1, new Animation(val => { value = val; View = localTopView; TryEvaluate(anim.Expression, _backingStore, localTopView); }, EvaluateDouble(anim.From, _backingStore, localTopView), EvaluateDouble(anim.To, _backingStore, localTopView), anim.EasingFunc, () => TryEvaluate(anim.FinishedExpression, _backingStore, localTopView)));
                     }
-                    a.Commit(currentViewAsView, "CurrentAnimation", 16, InDuration, null, null, () => false);
+                    a.Commit(_topView, "TheAnimation", 16, InDuration, null, null, () => false);
                 }
                 else
                 {
                     value = 1.0;
                     foreach (var anim in InAnimations)
-                        TryEvaluate(anim.Expression, _backingStore, true);
+                        TryEvaluate(anim.Expression, _backingStore, _topView);
                 }
             }
 
             // Visibilty has changed, so arrange it, in case it wasn't visible for the initial arrange call.
             (this as IView).InvalidateArrange();
         }
 
-        private bool TryEvaluate(ExpressionTree compiledExpression, PocoBackingStore backingStore, bool isInAnimation)
+        private double EvaluateDouble(ExpressionTree expression, PocoBackingStore backingStore, IView view)
         {
-            View = isInAnimation ? _currentView : _previousView;
+            View = view;
             try
             {
-                compiledExpression.Evaluate(backingStore);
-                return true;
+                OperandStack result = expression.Evaluate(backingStore);
+                IOperand operand = OperatorActions.PopAndResolve(result, backingStore);
+                double retval = Convert.ToDouble(operand.GetValue());
+                return retval;
             }
             catch (Exception ex)
             {
                 Debug.WriteLine(ex.Message);
-                return false;
+                return 0;
             }
         }
 
-        #endregion
+        private OperandStack TryEvaluate(ExpressionTree compiledExpression, PocoBackingStore backingStore, IView view)
+        {
+            //View = isInAnimation ? _currentView : _previousView;
+            View = view;
 
-        public double value { get; protected set; }
+            try
+            {
+                OperandStack retval = compiledExpression.Evaluate(backingStore);
+                return retval;
+            }
+            catch (Exception ex)
+            {
+                Debug.WriteLine(ex.Message);
+                return null;
+            }
+        }
+
+        #endregion
 
         #region InAnimationsProperty
 
@@ -305,7 +331,6 @@ private static void CreatedExpressionChanged(BindableObject bindable, object old
 
         #endregion
 
-
         #region AttachedProperties
 
         public static readonly BindableProperty MultiNameProperty =

FunctionZero.Maui.Controls/Controls/TransformContentPresenter/BackdropContentContainer.xaml

@@ -0,0 +1,18 @@
+<?xml version="1.0" encoding="utf-8" ?>
+<ContentView xmlns="http://schemas.microsoft.com/dotnet/2021/maui"
+             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
+             x:Class="FunctionZero.Maui.Controls.BackdropContentContainer"
+             x:Name="Self"
+             >
+    <!-- Any layout that allows a child to fill its render area will do. Custom layout would be better? -->
+    <ContentView.ControlTemplate>
+        <ControlTemplate>
+            <Grid>
+                <Grid BackgroundColor="{TemplateBinding BackdropColor, Mode=OneWay}" Opacity="{TemplateBinding BackdropOpacity, Mode=OneWay}"/>
+
+                <ContentPresenter />
+            </Grid>
+        </ControlTemplate>
+    </ContentView.ControlTemplate>
+
+</ContentView>

FunctionZero.Maui.Controls/Controls/TransformContentPresenter/BackdropContentContainer.xaml.cs

@@ -0,0 +1,43 @@
+namespace FunctionZero.Maui.Controls;
+
+public partial class BackdropContentContainer : ContentView
+{
+	public BackdropContentContainer()
+	{
+		InitializeComponent();
+	}
+
+    #region BackdropOpacityProperty
+
+    public static readonly BindableProperty BackdropOpacityProperty = BindableProperty.Create(nameof(BackdropOpacity), typeof(double), typeof(BackdropContentContainer), 1.0, BindingMode.OneWay, null, BackdropOpacityChanged);
+
+    public double BackdropOpacity
+    {
+        get { return (double)GetValue(BackdropOpacityProperty); }
+        set { SetValue(BackdropOpacityProperty, value); }
+    }
+
+    private static void BackdropOpacityChanged(BindableObject bindable, object oldValue, object newValue)
+    {
+        var self = (BackdropContentContainer)bindable;
+    }
+
+    #endregion
+
+    #region BackdropColorProperty
+
+    public static readonly BindableProperty BackdropColorProperty = BindableProperty.Create(nameof(BackdropColor), typeof(Color), typeof(BackdropContentContainer), Colors.Black, BindingMode.OneWay, null, BackdropColorChanged);
+
+    public Color BackdropColor
+    {
+        get { return (Color)GetValue(BackdropColorProperty); }
+        set { SetValue(BackdropColorProperty, value); }
+    }
+
+    private static void BackdropColorChanged(BindableObject bindable, object oldValue, object newValue)
+    {
+        var self = (BackdropContentContainer)bindable;
+    }
+
+    #endregion
+}

FunctionZero.Maui.Controls/FunctionZero.Maui.Controls.csproj

@@ -63,6 +63,12 @@
 		<PackageReference Include="FunctionZero.TreeListItemsSourceZero" Version="1.1.0-beta" />
 	</ItemGroup>
 
+	<ItemGroup>
+	  <Compile Update="Controls\TransformContentPresenter\BackdropContentContainer.xaml.cs">
+	    <DependentUpon>BackdropContentContainer.xaml</DependentUpon>
+	  </Compile>
+	</ItemGroup>
+
 	<ItemGroup>
 		<MauiXaml Update="Controls\Chevron.xaml">
 			<Generator>MSBuild:Compile</Generator>
@@ -82,6 +88,9 @@
 		<MauiXaml Update="Controls\MaskZero\MaskZero.xaml">
 			<Generator>MSBuild:Compile</Generator>
 		</MauiXaml>
+		<MauiXaml Update="Controls\TransformContentPresenter\BackdropContentContainer.xaml">
+		  <Generator>MSBuild:Compile</Generator>
+		</MauiXaml>
 		<MauiXaml Update="Controls\TreeView\TreeViewZero.xaml">
 			<Generator>MSBuild:Compile</Generator>
 		</MauiXaml>