QuickLook/QuickLook.Plugin/QuickLook.Plugin.PDFViewer/AsyncPageToThumbnailConverter.cs

// Copyright © 2018 Paddy Xu
// 
// This file is part of QuickLook program.
// 
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
// 
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
// 
// You should have received a copy of the GNU General Public License
// along with this program.  If not, see <http://www.gnu.org/licenses/>.

using System;
using System.Globalization;
using System.Threading.Tasks;
using System.Windows.Data;
using System.Windows.Media.Imaging;

namespace QuickLook.Plugin.PDFViewer
{
    internal class AsyncPageToThumbnailConverter : IMultiValueConverter
    {
        private static readonly BitmapImage Loading =
            new BitmapImage(
                new Uri("pack://application:,,,/QuickLook.Plugin.PdfViewer;component/Resources/loading.png"));

        public object Convert(object[] values, Type targetType, object parameter, CultureInfo culture)
        {
            if (values.Length < 2)
                throw new Exception("PageIdToImageConverter");

            if (!(values[0] is PdfDocumentWrapper handle)) return null;

            var pageId = (int) values[1];
            if (pageId < 0) return null;

            var task = Task.Run(() =>
            {
                try
                {
                    return handle.RenderThumbnail(pageId);
                }
                catch (Exception)
                {
                    return Loading;
                }
            });

            return new NotifyTaskCompletion<BitmapSource>(task, Loading);
        }

        public object[] ConvertBack(object value, Type[] targetTypes, object parameter, CultureInfo culture)
        {
            throw new NotImplementedException();
        }
    }
}