// Copyright © 2015 The CefSharp Authors. All rights reserved.
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//
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// Use of this source code is governed by a BSD-style license that can be found in the LICENSE file.
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using System;
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using System.Threading;
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using System.Threading.Tasks;
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using System.Threading.Tasks.Schedulers;
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namespace CefSharp.Internals
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{
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public sealed class MethodRunnerQueue : IMethodRunnerQueue
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{
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//Limit to 1 task per methodRunnerQueue
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//https://social.msdn.microsoft.com/Forums/vstudio/en-US/d0bcb415-fb1e-42e4-90f8-c43a088537fb/aborting-a-long-running-task-in-tpl?forum=parallelextensions
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private readonly TaskFactory methodRunnerQueueTaskFactory = new TaskFactory(new LimitedConcurrencyLevelTaskScheduler(1));
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private readonly JavascriptObjectRepository repository;
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private CancellationTokenSource cancellationTokenSource = new CancellationTokenSource();
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public event EventHandler<MethodInvocationCompleteArgs> MethodInvocationComplete;
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public MethodRunnerQueue(JavascriptObjectRepository repository)
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{
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this.repository = repository;
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}
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public void Dispose()
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{
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//Cancel all tasks associated with this MethoRunnerQueue
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cancellationTokenSource.Cancel();
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}
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public void Enqueue(MethodInvocation methodInvocation)
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{
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methodRunnerQueueTaskFactory.StartNew(() =>
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{
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var result = ExecuteMethodInvocation(methodInvocation);
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var handler = MethodInvocationComplete;
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if (!cancellationTokenSource.Token.IsCancellationRequested && handler != null)
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{
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handler(this, new MethodInvocationCompleteArgs(result));
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}
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}, cancellationTokenSource.Token);
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}
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private MethodInvocationResult ExecuteMethodInvocation(MethodInvocation methodInvocation)
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{
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object result = null;
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string exception;
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var success = false;
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//make sure we don't throw exceptions in the executor task
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try
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{
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success = repository.TryCallMethod(methodInvocation.ObjectId, methodInvocation.MethodName, methodInvocation.Parameters.ToArray(), out result, out exception);
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//We don't support Tasks by default
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if (success && result != null && (typeof(Task).IsAssignableFrom(result.GetType())))
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{
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//Use StringBuilder to improve the formatting/readability of the error message
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//I'm sure there's a better way I just cannot remember of the top of my head so going
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//with this for now, as it's only for error scenaiors I'm not concerned about performance.
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var builder = new System.Text.StringBuilder();
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builder.AppendLine("Your method returned a Task which is not supported by default you must set CefSharpSettings.ConcurrentTaskExecution = true; before creating your first ChromiumWebBrowser instance.");
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builder.AppendLine("This will likely change to the default at some point in the near future, subscribe to the issue link below to be notified of any changes.");
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builder.AppendLine("See https://github.com/cefsharp/CefSharp/issues/2758 for more details, please report any issues you have there, make sure you have an example ready that reproduces your problem.");
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success = false;
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result = null;
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exception = builder.ToString();
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}
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}
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catch (Exception e)
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{
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exception = e.Message;
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}
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return new MethodInvocationResult
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{
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BrowserId = methodInvocation.BrowserId,
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CallbackId = methodInvocation.CallbackId,
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FrameId = methodInvocation.FrameId,
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Message = exception,
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Result = result,
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Success = success
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};
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}
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}
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}
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