Shrlalgo.RvKits/WPFluent/Controls/ImageView/ImageView.cs

using System.Diagnostics;
using System.Runtime.CompilerServices;
using System.Windows.Controls;
using System.Windows.Input;
using System.Windows.Media.Animation;
using System.Windows.Media.Imaging;
using System.Windows.Threading;

namespace WPFluent.Controls;

public partial class ImageView : UserControl, INotifyPropertyChanged, IDisposable
{
    private Visibility _backgroundVisibility = Visibility.Visible;
    private Point? _dragInitPos = null!;
    private Uri _imageSource = null!;
    private bool _isZoomFactorFirstSet = true;
    private DateTime _lastZoomTime = DateTime.MinValue;
    private double _maxZoomFactor = 3d;
    private Visibility _metaIconVisibility = Visibility.Collapsed;
    private double _minZoomFactor = 0.1d;
    private BitmapScalingMode _renderMode = BitmapScalingMode.Linear;
    private bool _showZoomLevelInfo = true;
    private BitmapSource _source = null!;
    private double _zoomFactor = 1d;

    private bool _zoomToFit = true;
    private double _zoomToFitFactor;
    private bool _zoomWithControlKey;

    public ImageView()
    {
        InitializeComponent();

        Resources.MergedDictionaries.Clear();

        SizeChanged += ImagePanel_SizeChanged;
        ViewPanelImage.DoZoomToFit += (_, _) => DoZoomToFit();

        ViewPanel.PreviewMouseWheel += ViewPanel_PreviewMouseWheel;
        ViewPanel.MouseLeftButtonDown += ViewPanel_MouseLeftButtonDown;
        ViewPanel.MouseMove += ViewPanel_MouseMove;
        ViewPanel.MouseDoubleClick += ViewPanel_MouseDoubleClick;

        ViewPanel.ManipulationInertiaStarting += ViewPanel_ManipulationInertiaStarting;
        ViewPanel.ManipulationStarting += ViewPanel_ManipulationStarting;
        ViewPanel.ManipulationDelta += ViewPanel_ManipulationDelta;
    }

    public bool ZoomWithControlKey
    {
        get => _zoomWithControlKey;
        set
        {
            _zoomWithControlKey = value;
            OnPropertyChanged();
        }
    }

    public bool ShowZoomLevelInfo
    {
        get => _showZoomLevelInfo;
        set
        {
            if (value == _showZoomLevelInfo) return;
            _showZoomLevelInfo = value;
            OnPropertyChanged();
        }
    }

    public BitmapScalingMode RenderMode
    {
        get => _renderMode;
        set
        {
            _renderMode = value;
            OnPropertyChanged();
        }
    }

    public bool ZoomToFit
    {
        get => _zoomToFit;
        set
        {
            _zoomToFit = value;
            OnPropertyChanged();
        }
    }

    public Visibility MetaIconVisibility
    {
        get => _metaIconVisibility;
        set
        {
            _metaIconVisibility = value;
            OnPropertyChanged();
        }
    }

    public Visibility BackgroundVisibility
    {
        get => _backgroundVisibility;
        set
        {
            _backgroundVisibility = value;
            OnPropertyChanged();
        }
    }

    public double MinZoomFactor
    {
        get => _minZoomFactor;
        set
        {
            _minZoomFactor = value;
            OnPropertyChanged();
        }
    }

    public double MaxZoomFactor
    {
        get => _maxZoomFactor;
        set
        {
            _maxZoomFactor = value;
            OnPropertyChanged();
        }
    }

    public double ZoomToFitFactor
    {
        get => _zoomToFitFactor;
        private set
        {
            _zoomToFitFactor = value;
            OnPropertyChanged();
        }
    }

    public double ZoomFactor
    {
        get => _zoomFactor;
        private set
        {
            _zoomFactor = value;
            OnPropertyChanged();

            if (_isZoomFactorFirstSet)
            {
                _isZoomFactorFirstSet = false;
                return;
            }

            if (ShowZoomLevelInfo)
                ((Storyboard)ZoomLevelInfo.FindResource("StoryboardShowZoomLevelInfo")).Begin();
        }
    }

    public Uri ImageUriSource
    {
        get => _imageSource;
        set
        {
            _imageSource = value;

            OnPropertyChanged();
        }
    }

    public BitmapSource Source
    {
        get => _source;
        set
        {
            _source = value;
            OnPropertyChanged();

            if (ImageUriSource == null)
                ViewPanelImage.Source = _source;
        }
    }

    public void Dispose()
    {
        ViewPanelImage?.Dispose();
        ViewPanelImage = null;
    }

    public event PropertyChangedEventHandler? PropertyChanged;

    public event EventHandler<int>? ImageScrolled;

    public event EventHandler? ZoomChanged;

    private void ImagePanel_SizeChanged(object? sender, SizeChangedEventArgs e)
    {
        UpdateZoomToFitFactor();

        if (ZoomToFit)
            DoZoomToFit();
    }

    private void ViewPanel_ManipulationInertiaStarting(object? sender, ManipulationInertiaStartingEventArgs e)
    {
        e.TranslationBehavior = new InertiaTranslationBehavior
        {
            InitialVelocity = e.InitialVelocities.LinearVelocity,
            DesiredDeceleration = 10.0 * 96.0 / (1000.0 * 1000.0)
        };
    }

    private void ViewPanel_ManipulationStarting(object? sender, ManipulationStartingEventArgs e)
    {
        e.ManipulationContainer = ViewPanel;
        e.Mode = ManipulationModes.Scale | ManipulationModes.Translate;
    }

    private void ViewPanel_ManipulationDelta(object? sender, ManipulationDeltaEventArgs e)
    {
        var delta = e.DeltaManipulation;

        var newZoom = ZoomFactor + ZoomFactor * (delta.Scale.X - 1);

        Zoom(newZoom);

        ViewPanel.ScrollToHorizontalOffset(ViewPanel.HorizontalOffset - delta.Translation.X);
        ViewPanel.ScrollToVerticalOffset(ViewPanel.VerticalOffset - delta.Translation.Y);

        e.Handled = true;
    }

    private void ViewPanel_MouseLeftButtonDown(object? sender, MouseButtonEventArgs e)
    {
        e.MouseDevice.Capture(ViewPanel);

        _dragInitPos = e.GetPosition(ViewPanel);
        var temp = _dragInitPos.Value; // Point is a type value
        temp.Offset(ViewPanel.HorizontalOffset, ViewPanel.VerticalOffset);
        _dragInitPos = temp;
    }

    private void ViewPanel_MouseDoubleClick(object? sender, MouseButtonEventArgs e)
    {
        DoZoomToFit();
    }

    private void ViewPanel_MouseMove(object? sender, MouseEventArgs e)
    {
        if (!_dragInitPos.HasValue)
            return;

        if (e.LeftButton == MouseButtonState.Released)
        {
            e.MouseDevice.Capture(null);

            _dragInitPos = null;
            return;
        }

        e.Handled = true;

        var delta = _dragInitPos.Value - e.GetPosition(ViewPanel);

        ViewPanel.ScrollToHorizontalOffset(delta.X);
        ViewPanel.ScrollToVerticalOffset(delta.Y);
    }

    private void ViewPanel_PreviewMouseWheel(object? sender, MouseWheelEventArgs e)
    {
        e.Handled = true;

        // normal scroll when Control is not pressed, useful for PdfViewer
        if (ZoomWithControlKey && (Keyboard.Modifiers & ModifierKeys.Control) == 0)
        {
            ViewPanel.ScrollToVerticalOffset(ViewPanel.VerticalOffset - e.Delta);
            ImageScrolled?.Invoke(this, e.Delta);
            return;
        }

        // otherwise, perform normal zooming
        var newZoom = ZoomFactor + ZoomFactor * e.Delta / 120 * 0.1;

        Zoom(newZoom);
    }

    public Size GetScrollSize()
    {
        return new Size(ViewPanel.ScrollableWidth, ViewPanel.ScrollableHeight);
    }

    public Point GetScrollPosition()
    {
        return new Point(ViewPanel.HorizontalOffset, ViewPanel.VerticalOffset);
    }

    public void SetScrollPosition(Point point)
    {
        ViewPanel.ScrollToHorizontalOffset(point.X);
        ViewPanel.ScrollToVerticalOffset(point.Y);
    }

    public void DoZoomToFit()
    {
        UpdateZoomToFitFactor();

        Zoom(ZoomToFitFactor, false, true);
    }

    private void UpdateZoomToFitFactor()
    {
        if (ViewPanelImage?.Source == null)
        {
            ZoomToFitFactor = 1d;
            return;
        }

        var factor = Math.Min(ViewPanel.ActualWidth / ViewPanelImage.Source.Width,
            ViewPanel.ActualHeight / ViewPanelImage.Source.Height);

        ZoomToFitFactor = factor;
    }

    public void ResetZoom()
    {
        ZoomToFitFactor = 1;
        Zoom(1d, true, ZoomToFit);
    }

    public void Zoom(double factor, bool suppressEvent = false, bool isToFit = false)
    {
        if (ViewPanelImage?.Source == null)
            return;

        // pause when fit width
        if (ZoomFactor < ZoomToFitFactor && factor > ZoomToFitFactor
            || ZoomFactor > ZoomToFitFactor && factor < ZoomToFitFactor)
        {
            factor = ZoomToFitFactor;
            ZoomToFit = true;
        }
        // pause when 100%
        else if (ZoomFactor < 1 && factor > 1 || ZoomFactor > 1 && factor < 1)
        {
            factor = 1;
            ZoomToFit = false;
        }
        else
        {
            if (!isToFit)
                ZoomToFit = false;
        }

        factor = Math.Max(factor, MinZoomFactor);
        factor = Math.Min(factor, MaxZoomFactor);

        ZoomFactor = factor;

        var position = ZoomToFit
            ? new Point(ViewPanelImage.Source.Width / 2, ViewPanelImage.Source.Height / 2)
            : Mouse.GetPosition(ViewPanelImage);

        ViewPanelImage.LayoutTransform = new ScaleTransform(factor, factor);

        ViewPanel.InvalidateMeasure();

        // critical for calculating offset
        ViewPanel.ScrollToHorizontalOffset(0);
        ViewPanel.ScrollToVerticalOffset(0);
        UpdateLayout();

        var offset = ViewPanelImage.TranslatePoint(position, ViewPanel) - Mouse.GetPosition(ViewPanel);
        ViewPanel.ScrollToHorizontalOffset(offset.X);
        ViewPanel.ScrollToVerticalOffset(offset.Y);
        UpdateLayout();

        if (!suppressEvent)
            FireZoomChangedEvent();
    }

    private void FireZoomChangedEvent()
    {
        _lastZoomTime = DateTime.Now;

        Task.Delay(500).ContinueWith(t =>
        {
            if (DateTime.Now - _lastZoomTime < TimeSpan.FromSeconds(0.5))
                return;

            Debug.WriteLine($"FireZoomChangedEvent fired: {Environment.CurrentManagedThreadId}");

            Dispatcher.BeginInvoke(new Action(() => ZoomChanged?.Invoke(this, new EventArgs())),
                DispatcherPriority.Background);
        });
    }

    protected virtual void OnPropertyChanged([CallerMemberName] string propertyName = null!)
    {
        PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
    }

    public void ScrollToTop()
    {
        ViewPanel.ScrollToTop();
    }

    public void ScrollToBottom()
    {
        ViewPanel.ScrollToBottom();
    }
}