From 4bd187d362ada2fe60b8010fb1525c47e5173bae Mon Sep 17 00:00:00 2001
From: amwx <armccormickwx@gmail.com>
Date: Thu, 18 Mar 2021 21:28:40 -0500
Subject: [PATCH] Add MenuFlyout

---
 src/Avalonia.Controls/Flyouts/MenuFlyout.cs   | 87 +++++++++++++++++++
 .../Flyouts/MenuFlyoutPresenter.cs            | 36 ++++++++
 .../Accents/FluentControlResourcesDark.xaml   |  5 ++
 .../Accents/FluentControlResourcesLight.xaml  |  5 ++
 .../Controls/FluentControls.xaml              |  2 +
 .../Controls/FlyoutPresenter.xaml             |  5 ++
 .../Controls/MenuFlyoutPresenter.xaml         | 36 ++++++++
 7 files changed, 176 insertions(+)
 create mode 100644 src/Avalonia.Controls/Flyouts/MenuFlyout.cs
 create mode 100644 src/Avalonia.Controls/Flyouts/MenuFlyoutPresenter.cs
 create mode 100644 src/Avalonia.Themes.Fluent/Controls/MenuFlyoutPresenter.xaml

diff --git a/src/Avalonia.Controls/Flyouts/MenuFlyout.cs b/src/Avalonia.Controls/Flyouts/MenuFlyout.cs
new file mode 100644
index 0000000000..8eea5f211d
--- /dev/null
+++ b/src/Avalonia.Controls/Flyouts/MenuFlyout.cs
@@ -0,0 +1,87 @@
+using System.Collections;
+using System.Collections.Specialized;
+using Avalonia.Collections;
+using Avalonia.Controls.Primitives;
+using Avalonia.Controls.Templates;
+using Avalonia.Input;
+using Avalonia.Metadata;
+using Avalonia.Styling;
+
+#nullable enable
+
+namespace Avalonia.Controls
+{
+    public class MenuFlyout : FlyoutBase
+    {
+        public MenuFlyout()
+        {
+            _items = new AvaloniaList<object>();
+        }
+
+        public static readonly DirectProperty<MenuFlyout, IEnumerable> ItemsProperty =
+            ItemsControl.ItemsProperty.AddOwner<MenuFlyout>(x => x.Items,
+                (x, v) => x.Items = v);
+
+        public static readonly DirectProperty<MenuFlyout, IDataTemplate?> ItemTemplateProperty =
+            AvaloniaProperty.RegisterDirect<MenuFlyout, IDataTemplate?>(nameof(ItemTemplate),
+                x => x.ItemTemplate, (x, v) => x.ItemTemplate = v);
+
+        public Styles? FlyoutPresenterStyle
+        {
+            get
+            {
+                if (_styles == null)
+                {
+                    _styles = new Styles();
+                    _styles.CollectionChanged += OnMenuFlyoutPresenterStyleChanged;
+                }
+
+                return _styles;
+            }
+        }
+
+        [Content]
+        public IEnumerable Items
+        {
+            get => _items;
+            set => SetAndRaise(ItemsProperty, ref _items, value);
+        }
+
+        public IDataTemplate? ItemTemplate
+        {
+            get => _itemTemplate;
+            set => SetAndRaise(ItemTemplateProperty, ref _itemTemplate, value);
+        }
+
+        private Styles? _styles;
+        private bool _stylesDirty = true;
+        private IEnumerable _items;
+        private IDataTemplate? _itemTemplate;
+
+        protected override Control CreatePresenter()
+        {
+            return new MenuFlyoutPresenter
+            {
+                [!ItemsControl.ItemsProperty] = this[!ItemsProperty],
+                [!ItemsControl.ItemTemplateProperty] = this[!ItemTemplateProperty]
+            };
+        }
+
+        protected override void OnOpened()
+        {
+            if (_styles != null && _stylesDirty)
+            {
+                // Presenter for flyout generally shouldn't be public, so
+                // we should be ok to just reset the styles
+                _popup.Child.Styles.Clear();
+                _popup.Child.Styles.Add(_styles);
+            }
+            base.OnOpened();
+        }
+
+        private void OnMenuFlyoutPresenterStyleChanged(object sender, NotifyCollectionChangedEventArgs e)
+        {
+            _stylesDirty = true;
+        }
+    }
+}
diff --git a/src/Avalonia.Controls/Flyouts/MenuFlyoutPresenter.cs b/src/Avalonia.Controls/Flyouts/MenuFlyoutPresenter.cs
new file mode 100644
index 0000000000..7e59d824fa
--- /dev/null
+++ b/src/Avalonia.Controls/Flyouts/MenuFlyoutPresenter.cs
@@ -0,0 +1,36 @@
+using Avalonia.Controls.Generators;
+using Avalonia.Controls.Platform;
+using Avalonia.Controls.Primitives;
+using Avalonia.LogicalTree;
+
+namespace Avalonia.Controls
+{
+    public class MenuFlyoutPresenter : MenuBase
+    {
+        public MenuFlyoutPresenter()
+            :base(new DefaultMenuInteractionHandler(true))
+        {
+
+        }
+
+        public override void Close()
+        {
+            // DefaultMenuInteractionHandler calls this
+            var host = this.FindLogicalAncestorOfType<Popup>();
+            if (host != null)
+            {
+                host.IsOpen = false;
+            }
+        }
+
+        public override void Open()
+        {
+            //Ignore
+        }
+
+        protected override IItemContainerGenerator CreateItemContainerGenerator()
+        {
+            return new MenuItemContainerGenerator(this);
+        }
+    }
+}
diff --git a/src/Avalonia.Themes.Fluent/Accents/FluentControlResourcesDark.xaml b/src/Avalonia.Themes.Fluent/Accents/FluentControlResourcesDark.xaml
index abc02a6371..ae1fe42031 100644
--- a/src/Avalonia.Themes.Fluent/Accents/FluentControlResourcesDark.xaml
+++ b/src/Avalonia.Themes.Fluent/Accents/FluentControlResourcesDark.xaml
@@ -809,5 +809,10 @@
     <StaticResource x:Key="CalendarDatePickerForeground" ResourceKey="SystemControlForegroundBaseHighBrush" />
     <StaticResource x:Key="CalendarDatePickerBorderBrush" ResourceKey="SystemControlForegroundBaseMediumBrush" />
     <Thickness x:Key="CalendarDatePickerBorderThemeThickness">1</Thickness>
+
+    <!-- Resources for FlyoutPresenter.xaml -->
+    <StaticResource x:Key="FlyoutPresenterBackground" ResourceKey="SystemControlBackgroundChromeMediumLowBrush" />
+    <StaticResource x:Key="FlyoutBorderThemeBrush" ResourceKey="SystemControlForegroundChromeHighBrush" />
+
   </Style.Resources>
 </Style>
diff --git a/src/Avalonia.Themes.Fluent/Accents/FluentControlResourcesLight.xaml b/src/Avalonia.Themes.Fluent/Accents/FluentControlResourcesLight.xaml
index 6a2a04f732..5af24f57a8 100644
--- a/src/Avalonia.Themes.Fluent/Accents/FluentControlResourcesLight.xaml
+++ b/src/Avalonia.Themes.Fluent/Accents/FluentControlResourcesLight.xaml
@@ -807,5 +807,10 @@
     <StaticResource x:Key="CalendarDatePickerForeground" ResourceKey="SystemControlForegroundBaseHighBrush" />
     <StaticResource x:Key="CalendarDatePickerBorderBrush" ResourceKey="SystemControlForegroundBaseMediumBrush" />
     <Thickness x:Key="CalendarDatePickerBorderThemeThickness">1</Thickness>
+
+    <!-- Resources for FlyoutPresenter.xaml -->
+    <StaticResource x:Key="FlyoutPresenterBackground" ResourceKey="SystemControlBackgroundChromeMediumLowBrush" />
+    <StaticResource x:Key="FlyoutBorderThemeBrush" ResourceKey="SystemControlForegroundChromeHighBrush" />
+    
   </Style.Resources>
 </Style>
diff --git a/src/Avalonia.Themes.Fluent/Controls/FluentControls.xaml b/src/Avalonia.Themes.Fluent/Controls/FluentControls.xaml
index 0acb8f4f6e..16e05ffdfd 100644
--- a/src/Avalonia.Themes.Fluent/Controls/FluentControls.xaml
+++ b/src/Avalonia.Themes.Fluent/Controls/FluentControls.xaml
@@ -59,4 +59,6 @@
   <StyleInclude Source="avares://Avalonia.Themes.Fluent/Controls/SplitView.xaml"/>
   <StyleInclude Source="avares://Avalonia.Themes.Fluent/Controls/DatePicker.xaml"/>  
   <StyleInclude Source="avares://Avalonia.Themes.Fluent/Controls/TimePicker.xaml"/>  
+  <StyleInclude Source="avares://Avalonia.Themes.Fluent/Controls/FlyoutPresenter.xaml"/>
+  <StyleInclude Source="avares://Avalonia.Themes.Fluent/Controls/MenuFlyoutPresenter.xaml"/>
 </Styles>
diff --git a/src/Avalonia.Themes.Fluent/Controls/FlyoutPresenter.xaml b/src/Avalonia.Themes.Fluent/Controls/FlyoutPresenter.xaml
index 2be49d007b..3a8df060fa 100644
--- a/src/Avalonia.Themes.Fluent/Controls/FlyoutPresenter.xaml
+++ b/src/Avalonia.Themes.Fluent/Controls/FlyoutPresenter.xaml
@@ -1,4 +1,9 @@
 <Styles xmlns="https://github.com/avaloniaui" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
+  <Styles.Resources>
+    <Thickness x:Key="FlyoutBorderThemeThickness">1</Thickness>
+    <Thickness x:Key="FlyoutBorderThemePadding">0</Thickness>
+  </Styles.Resources>
+  
   <Style Selector="FlyoutPresenter">
     <Setter Property="HorizontalContentAlignment" Value="Stretch" />
     <Setter Property="VerticalContentAlignment" Value="Stretch" />
diff --git a/src/Avalonia.Themes.Fluent/Controls/MenuFlyoutPresenter.xaml b/src/Avalonia.Themes.Fluent/Controls/MenuFlyoutPresenter.xaml
new file mode 100644
index 0000000000..41a6e1cb65
--- /dev/null
+++ b/src/Avalonia.Themes.Fluent/Controls/MenuFlyoutPresenter.xaml
@@ -0,0 +1,36 @@
+<Styles xmlns="https://github.com/avaloniaui" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
+  
+  <Style Selector="MenuFlyoutPresenter">
+    <Setter Property="Background" Value="{DynamicResource MenuFlyoutPresenterBackground}" />
+    <Setter Property="BorderBrush" Value="{DynamicResource MenuFlyoutPresenterBorderBrush}" />
+    <Setter Property="BorderThickness" Value="{DynamicResource MenuFlyoutPresenterBorderThemeThickness}" />
+    <Setter Property="Padding" Value="{DynamicResource MenuFlyoutPresenterThemePadding}" />
+    <Setter Property="MaxWidth" Value="{DynamicResource FlyoutThemeMaxWidth}" />
+    <Setter Property="MinHeight" Value="{DynamicResource MenuFlyoutThemeMinHeight}" />
+    <Setter Property="ScrollViewer.HorizontalScrollBarVisibility" Value="Auto" />
+    <Setter Property="ScrollViewer.VerticalScrollBarVisibility" Value="Auto" />
+    <Setter Property="Template">
+      <ControlTemplate>
+        <Border Name="LayoutRoot"
+                Background="{TemplateBinding Background}"
+                BorderBrush="{TemplateBinding BorderBrush}"
+                BorderThickness="{TemplateBinding BorderThickness}"
+                Padding="{DynamicResource FlyoutBorderThemePadding}">
+          <ScrollViewer HorizontalScrollBarVisibility="{TemplateBinding ScrollViewer.HorizontalScrollBarVisibility}"
+                        VerticalScrollBarVisibility="{TemplateBinding ScrollViewer.VerticalScrollBarVisibility}">
+            <ItemsPresenter Name="PART_ItemsPresenter"
+                            Items="{TemplateBinding Items}"
+                            ItemsPanel="{TemplateBinding ItemsPanel}"
+                            ItemTemplate="{TemplateBinding ItemTemplate}"
+                            Margin="{DynamicResource MenuFlyoutScrollerMargin}"
+                            KeyboardNavigation.TabNavigation="Continue"
+                            Grid.IsSharedSizeScope="True" />
+          </ScrollViewer>
+        </Border>
+      </ControlTemplate>
+    </Setter>
+  </Style>
+  <Style Selector="MenuFlyoutPresenter /template/ Border#LayoutRoot">
+    <Setter Property="CornerRadius" Value="{DynamicResource OverlayCornerRadius}" />
+  </Style>
+</Styles>