'初始化'

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2020-06-10 a610f2ab6e543d2cb78c1ef212ac6a74ddc067d9

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// Copyright © 2015 The CefSharp Authors. All rights reserved.
//
// Use of this source code is governed by a BSD-style license that can be found in the LICENSE file.
 
using System;
using System.Threading.Tasks;
using CefSharp.Internals;
 
namespace CefSharp
{
    /// <summary>
    /// Provides a callback implementation of <see cref="IPrintToPdfCallback"/>.
    /// </summary>
    public sealed class TaskPrintToPdfCallback : IPrintToPdfCallback
    {
        private readonly TaskCompletionSource<bool> taskCompletionSource = new TaskCompletionSource<bool>();
        private volatile bool isDisposed;
        private bool onComplete; //Only ever accessed on the same CEF thread, so no need for thread safety
 
        /// <summary>
        /// Task used to await this callback
        /// </summary>
        public Task<bool> Task
        {
            get { return taskCompletionSource.Task; }
        }
 
        void IPrintToPdfCallback.OnPdfPrintFinished(string path, bool ok)
        {
            onComplete = true;
 
            taskCompletionSource.TrySetResultAsync(ok);
        }
 
        bool IPrintToPdfCallback.IsDisposed
        {
            get { return isDisposed; }
        }
 
        void IDisposable.Dispose()
        {
            var task = taskCompletionSource.Task;
 
            //If onComplete is false then IPrintToPdfCallback.OnPdfPrintFinished was never called,
            //so we'll set the result to false. Calling TrySetResultAsync multiple times 
            //can result in the issue outlined in https://github.com/cefsharp/CefSharp/pull/2349
            if (onComplete == false && task.IsCompleted == false)
            {
                taskCompletionSource.TrySetResultAsync(false);
            }
 
            isDisposed = true;
        }
    }
}