PhotosBrowser/ScalableGrid.cs

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using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using Windows.Foundation;
using Windows.UI.Xaml;
using Windows.UI.Xaml.Controls;
using Windows.UI.Xaml.Input;
using Windows.UI.Xaml.Media;

namespace PhotosBrowser
{
    public class ScalableGrid : Grid
    {
        private TransformGroup transformGroup;
        private ScaleTransform scaleTransform;
        private TranslateTransform translateTransform;

        public ScalableGrid()
        {
            this.scaleTransform = new ScaleTransform();
            this.translateTransform = new TranslateTransform();
            this.transformGroup = new TransformGroup();
            this.transformGroup.Children.Add(scaleTransform);
            this.transformGroup.Children.Add(translateTransform);
            this.RenderTransform = transformGroup;

            this.ManipulationMode = ManipulationModes.System | ManipulationModes.Scale;
            this.ManipulationDelta += ScalableGrid_ManipulationDelta;
            this.Loaded += ScalableGrid_Loaded;
            this.SizeChanged += (a, b) =>
            {
                this.scaleTransform.CenterX = this.ActualWidth / 2;
                this.scaleTransform.CenterY = this.ActualHeight / 2;
            };
            this.DoubleTapped += ScalableGrid_DoubleTapped;
        }

        private void ScalableGrid_DoubleTapped(object sender, DoubleTappedRoutedEventArgs e)
        {
            scaleTransform.ScaleX = scaleTransform.ScaleY = 1;
            this.translateTransform.X = 0;
            this.translateTransform.Y = 0;
            this.ManipulationMode = ManipulationModes.System | ManipulationModes.Scale;
        }

        private void ScalableGrid_Loaded(object sender, Windows.UI.Xaml.RoutedEventArgs e)
        {
            this.Loaded -= ScalableGrid_Loaded;
            scaleTransform.CenterX = this.ActualWidth / 2;
            scaleTransform.CenterY = this.ActualHeight / 2;
        }

        private void ScalableGrid_ManipulationDelta(object sender, Windows.UI.Xaml.Input.ManipulationDeltaRoutedEventArgs e)
        {
            //this.ManipulationMode = this.SetCurrentMainpulationModes();
            if (scaleTransform.ScaleX == 1 && scaleTransform.ScaleY == 1)
            {
                this.ManipulationMode = ManipulationModes.System | ManipulationModes.Scale;