Custom popup placement callback

api/Avalonia.nupkg.xml

@@ -19,6 +19,12 @@
     <Left>baseline/netstandard2.0/Avalonia.Base.dll</Left>
     <Right>target/netstandard2.0/Avalonia.Base.dll</Right>
   </Suppression>
+  <Suppression>
+    <DiagnosticId>CP0002</DiagnosticId>
+    <Target>M:Avalonia.Controls.Primitives.IPopupHost.ConfigurePosition(Avalonia.Visual,Avalonia.Controls.PlacementMode,Avalonia.Point,Avalonia.Controls.Primitives.PopupPositioning.PopupAnchor,Avalonia.Controls.Primitives.PopupPositioning.PopupGravity,Avalonia.Controls.Primitives.PopupPositioning.PopupPositionerConstraintAdjustment,System.Nullable{Avalonia.Rect})</Target>
+    <Left>baseline/netstandard2.0/Avalonia.Controls.dll</Left>
+    <Right>target/netstandard2.0/Avalonia.Controls.dll</Right>
+  </Suppression>
   <Suppression>
     <DiagnosticId>CP0002</DiagnosticId>
     <Target>M:Avalonia.Controls.Screens.#ctor(Avalonia.Platform.IScreenImpl)</Target>
@@ -43,6 +49,12 @@
     <Left>baseline/netstandard2.0/Avalonia.Controls.dll</Left>
     <Right>target/netstandard2.0/Avalonia.Controls.dll</Right>
   </Suppression>
+  <Suppression>
+    <DiagnosticId>CP0006</DiagnosticId>
+    <Target>M:Avalonia.Controls.Primitives.IPopupHost.ConfigurePosition(Avalonia.Controls.Primitives.PopupPositioning.PopupPositionRequest)</Target>
+    <Left>baseline/netstandard2.0/Avalonia.Controls.dll</Left>
+    <Right>target/netstandard2.0/Avalonia.Controls.dll</Right>
+  </Suppression>
   <Suppression>
     <DiagnosticId>CP0009</DiagnosticId>
     <Target>T:Avalonia.Controls.Screens</Target>

samples/ControlCatalog/Pages/FlyoutsPage.axaml

@@ -222,7 +222,15 @@
                                 </Flyout>
                             </Button.Flyout>
                         </Button>
-
+                        <Button Content="Placement=Custom">
+                            <Button.Flyout>
+                                <Flyout Placement="Custom" CustomPopupPlacementCallback="CustomPlacementCallback">
+                                    <Panel Width="100" Height="100">
+                                        <TextBlock Text="Flyout Content!" />
+                                    </Panel>
+                                </Flyout>
+                            </Button.Flyout>
+                        </Button>
                     </UniformGrid>
                 </Border>
             </StackPanel>
@@ -267,7 +275,6 @@
                                 </Flyout>
                             </Button.Flyout>
                         </Button>
-
                     </WrapPanel>
                 </Border>
             </StackPanel>

samples/ControlCatalog/Pages/FlyoutsPage.axaml.cs

@@ -1,5 +1,8 @@
+using System;
+using Avalonia;
 using Avalonia.Controls;
 using Avalonia.Controls.Primitives;
+using Avalonia.Controls.Primitives.PopupPositioning;
 using Avalonia.Interactivity;
 
 namespace ControlCatalog.Pages
@@ -71,5 +74,25 @@ private void SetXamlTexts()
                 "Then attach the flyout where you want it:\n" +
                 "<Button Content=\"Launch Flyout here\" Flyout=\"{StaticResource SharedFlyout}\" />";
         }
+
+        public void CustomPlacementCallback(CustomPopupPlacement placement)
+        {
+            var r = new Random().Next();
+            placement.Anchor = (r % 4) switch
+            {
+                1 => PopupAnchor.Top,
+                2 => PopupAnchor.Left,
+                3 => PopupAnchor.Right,
+                _ => PopupAnchor.Bottom,
+            };
+            placement.Gravity = (r % 4) switch
+            {
+                1 => PopupGravity.Top,
+                2 => PopupGravity.Left,
+                3 => PopupGravity.Right,
+                _ => PopupGravity.Bottom,
+            };
+            placement.Offset = new Point(r % 20, r % 20);
+        }
     }
 }

samples/ControlCatalog/Pages/ToolTipPage.xaml

@@ -5,31 +5,24 @@
                 Spacing="4">
         <TextBlock Classes="h2">A control which pops up a hint when a control is hovered</TextBlock>
 
-        <Grid RowDefinitions="Auto,Auto,Auto,Auto"
-              ColumnDefinitions="Auto,Auto"
-              Margin="0,16,0,0"
-              HorizontalAlignment="Center">
+        <UniformGrid Columns="2"
+                     Margin="0,16,0,0"
+                     HorizontalAlignment="Center">
             <ToggleSwitch Margin="5" 
-                    HorizontalAlignment="Center"
-                    IsChecked="{Binding Path=(ToolTip.ServiceEnabled), RelativeSource={RelativeSource AncestorType=UserControl}}"
-                    Content="Enable ToolTip service" />
-            <Border Grid.Column="0"
-                    Grid.Row="1"
-                    Background="{DynamicResource SystemAccentColor}"
+                          HorizontalAlignment="Center"
+                          IsChecked="{Binding Path=(ToolTip.ServiceEnabled), RelativeSource={RelativeSource AncestorType=UserControl}}"
+                          Content="Enable ToolTip service" />
+            <ToggleSwitch Margin="5"
+                          IsChecked="{Binding ElementName=Border, Path=(ToolTip.IsOpen)}"
+                          HorizontalAlignment="Center"
+                          Content="ToolTip Open" />
+            <Border Background="{DynamicResource SystemAccentColor}"
                     Margin="5"
                     Padding="50"
                     ToolTip.Tip="This is a ToolTip">
                 <TextBlock>Hover Here</TextBlock>
             </Border>
-            <ToggleSwitch Grid.Column="1"
-                      Margin="5"
-                      Grid.Row="0"
-                      IsChecked="{Binding ElementName=Border, Path=(ToolTip.IsOpen)}"
-                      HorizontalAlignment="Center"
-                      Content="ToolTip Open" />
             <Border Name="Border"
-                    Grid.Column="1"
-                    Grid.Row="1"
                     Background="{DynamicResource SystemAccentColor}"
                     Margin="5"
                     Padding="50"
@@ -42,8 +35,15 @@
                 </ToolTip.Tip>
                 <TextBlock>ToolTip bottom placement</TextBlock>
             </Border>
-            <Border Grid.Row="2"
-                    Background="{DynamicResource SystemAccentColor}"
+            <Border Background="{DynamicResource SystemAccentColor}"
+                    Margin="5"
+                    Padding="50"
+                    ToolTip.Placement="Custom"
+                    ToolTip.CustomPopupPlacementCallback="CustomPlacementCallback"
+                    ToolTip.Tip="Custom positioned tooltip">
+              <TextBlock>ToolTip custom placement</TextBlock>
+            </Border>
+            <Border Background="{DynamicResource SystemAccentColor}"
                     Margin="5"
                     Padding="50"
                     ToolTip.Tip="Hello"
@@ -67,33 +67,28 @@
               <TextBlock>Moving offset</TextBlock>
             </Border>
 
-            <Button Grid.Row="2" Grid.Column="1"
-                    IsEnabled="False"
+            <Button IsEnabled="False"
                     ToolTip.ShowOnDisabled="True"
                     ToolTip.Tip="This control is disabled"
                     Margin="5"
                     Padding="50">
               <TextBlock>ToolTip on a disabled control</TextBlock>
             </Button>
 
-          <Border Grid.Row="3"
-                  Grid.Column="0"
-                  Background="{DynamicResource SystemAccentColor}"
+          <Border Background="{DynamicResource SystemAccentColor}"
                   Margin="5"
                   Padding="50"
                   ToolTip.Tip="Outer tooltip">
             <TextBlock Background="{StaticResource SystemAccentColorDark1}" Padding="10" ToolTip.Tip="Inner tooltip" VerticalAlignment="Center">Nested ToolTips</TextBlock>
           </Border>
-
-          <Border Grid.Row="3"
-                  Grid.Column="1"
-                  Background="{DynamicResource SystemAccentColor}"
+
+          <Border Background="{DynamicResource SystemAccentColor}"
                   Margin="5"
                   Padding="50"
                   ToolTip.ToolTipOpening="ToolTipOpening"
                   ToolTip.Tip="Should never be visible">
             <TextBlock VerticalAlignment="Center">ToolTip replaced on the fly</TextBlock>
           </Border>
-        </Grid>
+        </UniformGrid>
     </StackPanel>
 </UserControl>

samples/ControlCatalog/Pages/ToolTipPage.xaml.cs

@@ -1,5 +1,8 @@
+using System;
+using Avalonia;
 using Avalonia.Controls;
 using Avalonia.Interactivity;
+using Avalonia.Controls.Primitives.PopupPositioning;
 using Avalonia.Markup.Xaml;
 
 namespace ControlCatalog.Pages
@@ -19,6 +22,27 @@ private void InitializeComponent()
         private void ToolTipOpening(object? sender, CancelRoutedEventArgs args)
         {
             ((Control)args.Source!).SetValue(ToolTip.TipProperty, "New tip set from ToolTipOpening.");
-        } 
+        }
+
+        public void CustomPlacementCallback(CustomPopupPlacement placement)
+        {
+            var r = new Random().Next();
+
+            placement.Anchor = (r % 4) switch
+            {
+                1 => PopupAnchor.Top,
+                2 => PopupAnchor.Left,
+                3 => PopupAnchor.Right,
+                _ => PopupAnchor.Bottom,
+            };
+            placement.Gravity = (r % 4) switch
+            {
+                1 => PopupGravity.Top,
+                2 => PopupGravity.Left,
+                3 => PopupGravity.Right,
+                _ => PopupGravity.Bottom,
+            };
+            placement.Offset = new Point(r % 20, r % 20);
+        }
     }
 }

src/Avalonia.Controls/ContextMenu.cs

@@ -82,6 +82,10 @@ public class ContextMenu : MenuBase, ISetterValue, IPopupHostProvider
         public static readonly StyledProperty<Control?> PlacementTargetProperty =
             Popup.PlacementTargetProperty.AddOwner<ContextMenu>();
 
+        /// <inheritdoc cref="Popup.CustomPopupPlacementCallbackProperty"/>
+        public static readonly StyledProperty<CustomPopupPlacementCallback?> CustomPopupPlacementCallbackProperty =
+            Popup.CustomPopupPlacementCallbackProperty.AddOwner<ContextMenu>();
+
         private Popup? _popup;
         private List<Control>? _attachedControls;
         private IInputElement? _previousFocus;
@@ -185,6 +189,13 @@ public Control? PlacementTarget
             set => SetValue(PlacementTargetProperty, value);
         }
 
+        /// <inheritdoc cref="Popup.CustomPopupPlacementCallback"/>
+        public CustomPopupPlacementCallback? CustomPopupPlacementCallback
+        {
+            get => GetValue(CustomPopupPlacementCallbackProperty);
+            set => SetValue(CustomPopupPlacementCallbackProperty, value);
+        }
+
         /// <summary>
         /// Occurs when the value of the
         /// <see cref="P:Avalonia.Controls.ContextMenu.IsOpen" />
@@ -340,6 +351,7 @@ private void Open(Control control, Control placementTarget, PlacementMode placem
             _popup.PlacementConstraintAdjustment = PlacementConstraintAdjustment;
             _popup.PlacementGravity = PlacementGravity;
             _popup.PlacementRect = PlacementRect;
+            _popup.CustomPopupPlacementCallback = CustomPopupPlacementCallback;
             _popup.WindowManagerAddShadowHint = WindowManagerAddShadowHint;
             IsOpen = true;
             _popup.IsOpen = true;

src/Avalonia.Controls/ContextRequestedEventArgs.cs

@@ -26,6 +26,13 @@ public ContextRequestedEventArgs(PointerEventArgs pointerEventArgs)
             _pointerEventArgs = pointerEventArgs;
         }
 
+        /// <inheritdoc cref="ContextRequestedEventArgs()" />
+        public ContextRequestedEventArgs(ContextRequestedEventArgs contextRequestedEventArgs)
+            : this()
+        {
+            _pointerEventArgs = contextRequestedEventArgs._pointerEventArgs;
+        }
+
         /// <summary>
         /// Gets the x- and y-coordinates of the pointer position, optionally evaluated against a coordinate origin of a supplied <see cref="Control"/>.
         /// </summary>

src/Avalonia.Controls/Flyouts/PopupFlyoutBase.cs

@@ -30,11 +30,15 @@ public abstract class PopupFlyoutBase : FlyoutBase, IPopupHostProvider
         /// <inheritdoc cref="Popup.PlacementAnchorProperty"/>
         public static readonly StyledProperty<PopupAnchor> PlacementAnchorProperty =
             Popup.PlacementAnchorProperty.AddOwner<PopupFlyoutBase>();
-        
+
         /// <inheritdoc cref="Popup.PlacementAnchorProperty"/>
         public static readonly StyledProperty<PopupGravity> PlacementGravityProperty =
             Popup.PlacementGravityProperty.AddOwner<PopupFlyoutBase>();
 
+        /// <inheritdoc cref="Popup.CustomPopupPlacementCallbackProperty"/>
+        public static readonly StyledProperty<CustomPopupPlacementCallback?> CustomPopupPlacementCallbackProperty =
+            Popup.CustomPopupPlacementCallbackProperty.AddOwner<PopupFlyoutBase>();
+
         /// <summary>
         /// Defines the <see cref="ShowMode"/> property
         /// </summary>
@@ -112,6 +116,13 @@ public double VerticalOffset
             set => SetValue(VerticalOffsetProperty, value);
         }
 
+        /// <inheritdoc cref="Popup.CustomPopupPlacementCallback"/>
+        public CustomPopupPlacementCallback? CustomPopupPlacementCallback
+        {
+            get => GetValue(CustomPopupPlacementCallbackProperty);
+            set => SetValue(CustomPopupPlacementCallbackProperty, value);
+        }
+
         /// <summary>
         /// Gets or sets the desired ShowMode
         /// </summary>
@@ -445,6 +456,7 @@ private void PositionPopup(bool showAtPointer)
             Popup.HorizontalOffset = HorizontalOffset;
             Popup.PlacementAnchor = PlacementAnchor;
             Popup.PlacementGravity = PlacementGravity;
+            Popup.CustomPopupPlacementCallback = CustomPopupPlacementCallback;
             if (showAtPointer)
             {
                 Popup.Placement = PlacementMode.Pointer;

src/Avalonia.Controls/PlacementMode.cs

@@ -81,6 +81,11 @@ public enum PlacementMode
         /// <summary>
         /// Preferred location is to the right of the target element, with the bottom edge of popup aligned with bottom edge of the target element.
         /// </summary>
-        RightEdgeAlignedBottom
+        RightEdgeAlignedBottom,
+
+        /// <summary>
+        /// A position and repositioning behavior that is defined by the <see cref="Popup.CustomPopupPlacementCallback"/> property.
+        /// </summary>
+        Custom
     }
 }

src/Avalonia.Controls/Primitives/IPopupHost.cs

@@ -1,6 +1,7 @@
 using System;
 using Avalonia.Controls.Presenters;
 using Avalonia.Controls.Primitives.PopupPositioning;
+using Avalonia.Diagnostics;
 using Avalonia.Input;
 using Avalonia.Media;
 using Avalonia.Metadata;
@@ -17,6 +18,7 @@ namespace Avalonia.Controls.Primitives
     /// on an <see cref="OverlayLayer"/>.
     /// </remarks>
     [NotClientImplementable]
+    [Unstable(ObsoletionMessages.MayBeRemovedInAvalonia12)]
     public interface IPopupHost : IDisposable, IFocusScope
     {
         /// <summary>
@@ -79,20 +81,7 @@ public interface IPopupHost : IDisposable, IFocusScope
         /// Configures the position of the popup according to a target control and a set of
         /// placement parameters.
         /// </summary>
-        /// <param name="target">The placement target.</param>
-        /// <param name="placement">The placement mode.</param>
-        /// <param name="offset">The offset, in device-independent pixels.</param>
-        /// <param name="anchor">The anchor point.</param>
-        /// <param name="gravity">The popup gravity.</param>
-        /// <param name="constraintAdjustment">Defines how a popup position will be adjusted if the unadjusted position would result in the popup being partly constrained.</param>
-        /// <param name="rect">
-        /// The anchor rect. If null, the bounds of <paramref name="target"/> will be used.
-        /// </param>
-        void ConfigurePosition(Visual target, PlacementMode placement, Point offset,
-            PopupAnchor anchor = PopupAnchor.None,
-            PopupGravity gravity = PopupGravity.None,
-            PopupPositionerConstraintAdjustment constraintAdjustment = PopupPositionerConstraintAdjustment.All,
-            Rect? rect = null);
+        void ConfigurePosition(PopupPositionRequest positionRequest);
 
         /// <summary>
         /// Sets the control to display in the popup.