ShrlAlgoToolkit/WPFDark/Controls/BiaFilteringComboBoxEventHandler.cs

using System;
using System.ComponentModel;
using System.Diagnostics.CodeAnalysis;
using System.Linq;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Controls.Primitives;
using System.Windows.Input;
using System.Windows.Threading;
using Jewelry.Memory;

using WPFDark.Internals;

namespace WPFDark.Controls
{
    // ReSharper disable once UnusedMember.Global
    public partial class BiaFilteringComboBoxEventHandler
    {
        private void ClearButton_OnClick(object sender, RoutedEventArgs e)
        {
            var button = (FrameworkElement) sender;
            var wordTextBox = (TextBox) button.Tag;

            wordTextBox.Text = "";
            wordTextBox.Focus();
        }

        private void ClearButton_OnLoaded(object sender, RoutedEventArgs e)
        {
            var button = (FrameworkElement) sender;
            var wordTextBox = (TextBox) button.Tag;

            wordTextBox.Dispatcher?.BeginInvoke(new Action(() => wordTextBox.Focus()));
        }

        [SuppressMessage("ReSharper", "PossiblyImpureMethodCallOnReadonlyVariable")]
        private void WordTextBox_OnKeyDown(object sender, KeyEventArgs e)
        {
            if (e.Key != Key.Down &&
                e.Key != Key.Up)
                return;

            var textBox = (FrameworkElement) sender;
            var sv = textBox.Parent.Descendants().OfType<ScrollViewer>().First();

            if (e.Key == Key.Down)
                sv.ScrollToHome();
            else
                sv.ScrollToBottom();

            // ※.VirtualizingStackPanelなためスクロールを済ませてからアイテムを探しに行く
            sv.Dispatcher?.BeginInvoke(
                DispatcherPriority.Input,
                new Action(() =>
                {
                    using var items = textBox.Parent.Descendants().OfType<ComboBoxItem>().ToTempBuffer(512);

                    if (items.Length == 0)
                        return;

                    var selectedItem = items.FirstOrDefault(x => x.IsSelected);
                    var isDown = e.Key == Key.Down;

                    if (selectedItem is null)
                    {
                        var item = isDown
                            ? items.FirstOrDefault()
                            : items.LastOrDefault();

                        if (item != null)
                            item.IsSelected = true;
                    }
                    else
                    {
                        var selectedItemIndex = items.IndexOf(selectedItem);
                        var nextIndex = selectedItemIndex + (isDown ? +1 : -1);

                        nextIndex = Math.Max(nextIndex, 0);
                        nextIndex = Math.Min(nextIndex, items.Length - 1);

                        var nextItem = items[nextIndex];
                        nextItem.IsSelected = true;
                    }

                    textBox.Focus();
                }));
        }

        private void Popup_OnClosed(object sender, EventArgs e)
        {
            var popup = (FrameworkElement) sender;
            var parent = popup.GetParent<BiaFilteringComboBox>();

            if (parent is null)
                return;

            parent.FilterWords = "";

            var expression = parent.GetBindingExpression(Selector.SelectedItemProperty);
            expression?.UpdateTarget();
        }

        private void Popup_OnOpened(object sender, EventArgs e)
        {
            var popup = (FrameworkElement) sender;

            UpdateClearButton(popup);
        }

        private void Popup_OnLoaded(object sender, RoutedEventArgs e)
        {
            var popup = (Popup) sender;
            var parent = popup.GetParent<BiaFilteringComboBox>();

            var descriptor = DependencyPropertyDescriptor.FromProperty(BiaFilteringComboBox.FilterWordsProperty,
                typeof(BiaFilteringComboBox));

            descriptor.AddValueChanged(parent, UpdateClearButtonHandler);
        }

        private void Popup_OnUnloaded(object sender, RoutedEventArgs e)
        {
            var popup = (Popup) sender;
            var parent = popup.GetParent<BiaFilteringComboBox>();

            var descriptor = DependencyPropertyDescriptor.FromProperty(BiaFilteringComboBox.FilterWordsProperty,
                typeof(BiaFilteringComboBox));

            descriptor.RemoveValueChanged(parent, UpdateClearButtonHandler);
        }

        private static void UpdateClearButtonHandler(object? sender, EventArgs e)
        {
            if (sender is FrameworkElement popup)
                UpdateClearButton(popup);
        }

        private static void UpdateClearButton(FrameworkElement popup)
        {
            var parent = popup.GetParent<BiaFilteringComboBox>();
            var clearButton = popup.Descendants().OfType<Button>().FirstOrDefault();

            if (clearButton != null)
                clearButton.IsEnabled = string.IsNullOrEmpty(parent?.FilterWords) == false;
        }
    }
}