The WPF Podcatcher Series - Part 2 (Structural Skinning)

using System;
using System.Linq;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Input;
using System.Windows.Media.Animation;
using Podder.Model;

namespace Podder.GrantHinkson.Views
{
    /// <summary>
    /// Interaction logic for PodcastsControlView.xaml
    /// </summary>
    public partial class PodcastsControlView : UserControl
    {
        #region Data

        private PodderDataSource _dataSource;
        private readonly Storyboard _closeAddPodcastDialogStoryboard;

        #endregion // Data

        #region Constructor

        public PodcastsControlView()
        {
            InitializeComponent();

            _closeAddPodcastDialogStoryboard = this.TryFindResource("CloseAddPodcastDialog") as Storyboard;

            // Grab a reference to the data source when it becomes available.
            this.DataContextChanged += delegate { _dataSource = base.DataContext as PodderDataSource; };

            // Scroll the selected Podcast into view.
            this.Loaded += delegate { this.PodcastsCarousel.ScrollInfo.SetHorizontalOffset(this.PodcastsCarousel.SelectedIndex); };

            this.PodcastsCarousel.PreviewKeyDown += PodcastsCarousel_PreviewKeyDown;
        }

        #endregion // Constructor

        #region Event Handlers
        #region Add Podcast Area
        void OnAddPodcastAreaClosed(object sender, EventArgs e)
        {
            if (_dataSource != null)
                _dataSource.Podcasts.NewPodcastInfo.FeedUrl = null;

            if (!this.btnAddPodcast.IsEnabled)
                this.btnAddPodcast.IsEnabled = true;
        }

        void OnAddPodcastAreaOpened(object sender, EventArgs e)
        {
            if (!this.IsMouseOverAddPodcastArea)
            {
                // If the user accidentally opened the "Add Podcast" 
                // area then close it for them, as a convenience.
                if (_closeAddPodcastDialogStoryboard != null)
                    _closeAddPodcastDialogStoryboard.Begin(this);
            }
            else
            {
                // We must disable the Add Podcast (+) button because mousing
                // over it while the TextBox is visible causes it to reset.
                // This is because its "mouseover" animations run again.
                if (this.btnAddPodcast.IsEnabled)
                    this.btnAddPodcast.IsEnabled = false;

                if (Commands.AutoDetectFeedUrlOnClipboard.CanExecute(null, this))
                {
                    Commands.AutoDetectFeedUrlOnClipboard.Execute(null, this);
                    CommandManager.InvalidateRequerySuggested();
                }
            }
        }

        /// <summary>
        /// Selects and scrolls the newly added Podcast into view, and erases new podcast URL.
        /// </summary>
        void OnPodcastAdded(object sender, EventArgs e)
        {
            if (_dataSource == null)
                return;

            string feedUrl = _dataSource.Podcasts.NewPodcastInfo.FeedUrl;
            var podcast = _dataSource.Podcasts.FirstOrDefault(p => p.RssUrl == feedUrl);
            if (podcast == null)
                return;

            int idx = this.PodcastsCarousel.Items.IndexOf(podcast);
            if (idx < 0)
                return;

            this.PodcastsCarousel.SelectedIndex = idx;
            this.PodcastsCarousel.ScrollInfo.SetHorizontalOffset(idx);

            _dataSource.Podcasts.NewPodcastInfo.FeedUrl = null;
            this.btnAddPodcast.IsEnabled = true;
        }
        #endregion // Add Podcast Area

        #region Buttons
        void btnCarouselNavPrev_Click(object sender, RoutedEventArgs e)
        {
            this.PodcastsCarousel.ScrollInfo.LineUp();
        }

        void btnCarouselNavNext_Click(object sender, RoutedEventArgs e)
        {
            this.PodcastsCarousel.ScrollInfo.LineDown();
        }
        #endregion Buttons

        #region PodcastsCarousel
        void PodcastsCarousel_PreviewKeyDown(object sender, KeyEventArgs e)
        {
            switch (e.Key)
            {
                case Key.Delete:
                    // Do not allow the user to delete via the Delete key because that bypasses the Delete command.
                    e.Handled = true;
                    break;

                case Key.Right:
                case Key.Down:
                    if (this.PodcastsCarousel.SelectedIndex == this.PodcastsCarousel.Items.Count - 1)
                    {
                        e.Handled = true;
                        this.PodcastsCarousel.SelectedIndex = 0;
                    }
                    break;

                case Key.Left:
                case Key.Up:
                    if (this.PodcastsCarousel.SelectedIndex == 0)
                    {
                        e.Handled = true;
                        this.PodcastsCarousel.SelectedIndex = this.PodcastsCarousel.Items.Count - 1;
                    }
                    break;
            }
        }
        #endregion // PodcastsCarousel
        #endregion // Event Handlers

        #region Private Helpers

        /// <summary>
        /// Returns true if the mouse cursor is over the "Add Podcasts" area of the UI.
        /// </summary>
        bool IsMouseOverAddPodcastArea
        {
            get
            {
                // The IsMouseOver property is not always accurate, so we manually detect if the cursor is over the controls.

                Point grpMousePos = Mouse.GetPosition(this.grpAddPodcast);
                Point btnMousePos = Mouse.GetPosition(this.btnAddPodcast);

                Rect grpAddPodcastBounds = new Rect(0, 0, this.grpAddPodcast.ActualWidth, this.grpAddPodcast.ActualHeight);
                Rect btnAddPodcastBounds = new Rect(0, 0, this.btnAddPodcast.ActualWidth, this.btnAddPodcast.ActualHeight);

                return grpAddPodcastBounds.Contains(grpMousePos) || btnAddPodcastBounds.Contains(btnMousePos);
            }
        }

        #endregion // Private Helpers
    }
}