add InputPaneAwareView

src/Avalonia.Controls/InputPaneAwareBehavior.cs

@@ -0,0 +1,9 @@
+namespace Avalonia.Controls
+{
+    public enum InputPaneAwareBehavior
+    {
+        None = 0,
+        Pan,
+        Resize
+    }
+}

src/Avalonia.Controls/InputPaneAwareView.cs

@@ -0,0 +1,147 @@
+using Avalonia.Animation;
+using Avalonia.Animation.Easings;
+using Avalonia.Controls.Platform;
+
+namespace Avalonia.Controls
+{
+    /// <summary>
+    /// A control that automatically adjusts its child position or height based on the input pane's height to ensure the content is visible.
+    /// </summary>
+    public class InputPaneAwareView : Decorator
+    {
+        private InputPaneAwareBehavior _behavior;
+        private IInputPane? _inputPane;
+        private bool _firstLayoutDone;
+
+        /// <summary>
+        /// Defines the <see cref="Behavior"/> property.
+        /// </summary>
+        public static readonly DirectProperty<InputPaneAwareView, InputPaneAwareBehavior> BehaviorProperty = AvaloniaProperty.RegisterDirect<InputPaneAwareView, InputPaneAwareBehavior>(
+            nameof(Behavior),
+            o => o.Behavior,
+            (o, x) => o.Behavior = x);
+
+        private static readonly StyledProperty<double> CurrentInputPanePaddingProperty = AvaloniaProperty.Register<InputPaneAwareView, double>(
+            nameof(CurrentInputPanePadding), coerce: (o, x) =>
+            {
+                return x;
+            });
+
+        /// <summary>
+        /// Gets or sets how the view reacts to the input pane state. 
+        /// </summary>
+        public InputPaneAwareBehavior Behavior
+        {
+            get => _behavior;
+            set => SetAndRaise(BehaviorProperty, ref _behavior, value);
+        }
+
+        private double CurrentInputPanePadding
+        {
+            get => GetValue(CurrentInputPanePaddingProperty);
+            set => SetValue(CurrentInputPanePaddingProperty, value);
+        }
+
+        static InputPaneAwareView()
+        {
+            AffectsMeasure<InputPaneAwareView>(BehaviorProperty, CurrentInputPanePaddingProperty);
+            AffectsArrange<InputPaneAwareView>(CurrentInputPanePaddingProperty);
+        }
+
+        protected override Size MeasureOverride(Size availableSize)
+        {
+            if (_inputPane != null && _firstLayoutDone && VisualRoot is { } root && Behavior == InputPaneAwareBehavior.Resize)
+            {
+                SetCurrentValue(PaddingProperty, new Thickness(0, 0, 0, CurrentInputPanePadding));
+            }
+            return base.MeasureOverride(availableSize);
+        }
+
+        protected override Size ArrangeOverride(Size finalSize)
+        {
+            _firstLayoutDone = true;
+
+            if (Behavior == InputPaneAwareBehavior.Pan)
+            {
+                Child?.Arrange(new Rect(new Point(0, -CurrentInputPanePadding), finalSize));
+
+                return finalSize;
+            }
+            else
+                return base.ArrangeOverride(finalSize);
+        }
+
+        protected override void OnAttachedToVisualTree(VisualTreeAttachmentEventArgs e)
+        {
+            base.OnAttachedToVisualTree(e);
+
+            _inputPane = TopLevel.GetTopLevel(this)?.InputPane;
+            _inputPane?.StateChanged += InputPaneAwareView_StateChanged;
+            EnsureInputPanePaddingApplied();
+        }
+
+        protected override void OnDetachedFromVisualTree(VisualTreeAttachmentEventArgs e)
+        {
+            base.OnDetachedFromVisualTree(e);
+            _inputPane?.StateChanged -= InputPaneAwareView_StateChanged;
+            _inputPane = null;
+            SetCurrentValue(PaddingProperty, default);
+#pragma warning disable AVP1012 // An AvaloniaObject should use SetCurrentValue when assigning its own StyledProperty or AttachedProperty values
+            CurrentInputPanePadding = 0;
+#pragma warning restore AVP1012 // An AvaloniaObject should use SetCurrentValue when assigning its own StyledProperty or AttachedProperty values
+        }
+
+        private void EnsureInputPanePaddingApplied()
+        {
+            SetCurrentValue(PaddingProperty, default);
+
+            if (_inputPane != null && _firstLayoutDone && this.VisualRoot is { } root && Behavior != InputPaneAwareBehavior.None)
+            {
+                var occludedRect = _inputPane.OccludedRect;
+
+                var transformMatrix = this.TransformToVisual(root) ?? Matrix.Identity;
+
+                var translatedRect = Bounds.TransformToAABB(transformMatrix);
+
+                var intersect = occludedRect.Intersect(translatedRect);
+
+#pragma warning disable AVP1012 // An AvaloniaObject should use SetCurrentValue when assigning its own StyledProperty or AttachedProperty values
+                CurrentInputPanePadding = intersect.Height;
+            }
+            else
+            {
+                CurrentInputPanePadding = 0;
+            }
+#pragma warning restore AVP1012 // An AvaloniaObject should use SetCurrentValue when assigning its own StyledProperty or AttachedProperty values
+        }
+
+        private void InputPaneAwareView_StateChanged(object? sender, InputPaneStateEventArgs e)
+        {
+            var transition = new DoubleTransition()
+            {
+                Property = CurrentInputPanePaddingProperty,
+                Duration = e.AnimationDuration,
+                Easing = e.Easing as Easing ?? new LinearEasing()
+            };
+
+            Transitions =
+            [
+                transition
+            ];
+
+            EnsureInputPanePaddingApplied();
+
+            InvalidateMeasure();
+        }
+
+        protected override void OnPropertyChanged(AvaloniaPropertyChangedEventArgs change)
+        {
+            base.OnPropertyChanged(change);
+
+            if(change.Property == BehaviorProperty)
+            {
+                EnsureInputPanePaddingApplied();
+            }
+        }
+    }
+}