Nuclex.Windows.Forms/Source/ProgressReporter/ProgressReporterForm.cs

#region Apache License 2.0
/*
Nuclex .NET Framework
Copyright (C) 2002-2024 Markus Ewald / Nuclex Development Labs

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/
#endregion // Apache License 2.0

using System;
using System.ComponentModel;
using System.Threading;
using System.Windows.Forms;

#if WITH_NUCLEX_SUPPORT_TRANSACTIONS

using Nuclex.Support.Scheduling;
using Nuclex.Support.Tracking;

namespace Nuclex.Windows.Forms {

  /// <summary>
  ///   Blocking progress dialog that prevents the user from accessing the application
  ///   window during a modal asynchronous processes.
  /// </summary>
  /// <example>
  ///   <code>
  ///     class Test : Nuclex.Support.Scheduling.ThreadOperation {
  ///
  ///       static void Main() {
  ///         Test myTest = new Test();
  ///         myTest.Begin();
  ///         Nuclex.Windows.Forms.ProgressReporterForm.Track(myTest);
  ///         myTest.End();
  ///       }
  ///
  ///       protected override void Execute() {
  ///         for(int i = 0; i &lt; 10000000; ++i) {
  ///           OnAsyncProgressUpdated((float)i / 10000000.0f);
  ///         }
  ///       }
  ///
  ///     }
  ///   </code>
  /// </example>
  public partial class ProgressReporterForm : Form {

    /// <summary>Initializes a new progress reporter</summary>
    internal ProgressReporterForm() {
      InitializeComponent();

      this.asyncEndedDelegate = new EventHandler(asyncEnded);
      this.asyncProgressChangedDelegate = new EventHandler<ProgressReportEventArgs>(
        asyncProgressChanged
      );
    }

    /// <summary>
    ///   Shows the progress reporter until the specified transaction has ended.
    /// </summary>
    /// <param name="transaction">
    ///   Transaction for whose duration to show the progress reporter
    /// </param>
    public static void Track(Transaction transaction) {
      Track(null, transaction);
    }

    /// <summary>
    ///   Shows the progress reporter until the specified transaction has ended.
    /// </summary>
    /// <param name="windowTitle">
    ///   Text to be shown in the progress reporter's title bar
    /// </param>
    /// <param name="transaction">
    ///   Process for whose duration to show the progress reporter
    /// </param>
    public static void Track(string windowTitle, Transaction transaction) {

      // Small optimization to avoid the lengthy control creation when the background
      // process has already ended. This is an accepted race condition: If the process
      // finishes right after this line, it doesn't change the outcome, it just
      // causes the progress dialog to be constructed needlessly.
      if(transaction.Ended) {
        return;
      }

      // Open the form and let it monitor the transaction's state
      using(ProgressReporterForm theForm = new ProgressReporterForm()) {
        theForm.track(windowTitle, transaction);
      }

    }

    /// <summary>Called when the user tries to close the form manually</summary>
    /// <param name="arguments">
    ///   Contains a flag that can be used to abort the close attempt
    /// </param>
    protected override void OnClosing(CancelEventArgs arguments) {
      base.OnClosing(arguments);

      // Only allow the form to close when the form is ready to close and the
      // transaction being tracked has also finished.
      arguments.Cancel = (Thread.VolatileRead(ref this.state) < 2);
    }

    /// <summary>
    ///   Shows the progress reporter until the specified transaction has ended.
    /// </summary>
    /// <param name="windowTitle">
    ///   Text to be shown in the progress reporter's title bar
    /// </param>
    /// <param name="transaction">
    ///   Transaction for whose duration to show the progress reporter
    /// </param>
    private void track(string windowTitle, Transaction transaction) {

      // Set the window title if the user wants to use a custom one
      if(windowTitle != null) {
        Text = windowTitle;
      }

      // Only enable the cancel button if the transaction can be aborted
      this.abortReceiver = (transaction as IAbortable);
      this.cancelButton.Enabled = (this.abortReceiver != null);

      // Make sure the progress bar control has been created (otherwise, we've got
      // a chance that BeginInvoke() would fail if the first progress notification
      // arrived before we called ShowDialog()!)
      { IntPtr tempDummy = this.progressBar.Handle; }

      // Subscribe the form to the transaction it is supposed to monitor.
      // Careful: With the new design, this can cause the asyncEndedDelegate()
      // callback to be called immediately and synchronously!
      transaction.AsyncEnded += this.asyncEndedDelegate;
      IProgressReporter progressReporter = transaction as IProgressReporter;
      if(progressReporter != null) {
        progressReporter.AsyncProgressChanged += this.asyncProgressChangedDelegate;
      }

      // The transaction might have ended before this line was reached, if that's
      // the case, we don't show the dialog at all.
      if(!transaction.Ended)
        ShowDialog();

      // We're done, unsubscribe from the transaction's events again
      progressReporter = transaction as IProgressReporter;
      if(progressReporter != null) {
        progressReporter.AsyncProgressChanged -= this.asyncProgressChangedDelegate;
      }
      transaction.AsyncEnded -= this.asyncEndedDelegate;

    }

    /// <summary>Called when the transaction has ended</summary>
    /// <param name="sender">Transaction that has ended</param>
    /// <param name="arguments">Not used</param>
    private void asyncEnded(object sender, EventArgs arguments) {

      // If the new state is 2, the form was ready to close (since the state
      // is incremented once when the form becomes ready to be closed)
      if(Interlocked.Increment(ref this.state) == 2) {

        // Close the dialog. Ensure the Close() method is invoked from the
        // same thread the dialog was created in.
        if(InvokeRequired) {
          Invoke(new MethodInvoker(Close));
        } else {
          Close();
        }

      }

    }

    /// <summary>Called when the tracked transaction's progress updates</summary>
    /// <param name="sender">Transaction whose progress has been updated</param>
    /// <param name="arguments">
    ///   Contains the new progress achieved by the transaction
    /// </param>
    private void asyncProgressChanged(object sender, ProgressReportEventArgs arguments) {

      // See if this is the first progress update we're receiving. If yes, we need to
      // switch the progress bar from marquee into its normal mode!
      int haveProgress = Interlocked.Exchange(ref this.areProgressUpdatesIncoming, 1);
      if(haveProgress == 0) {
        this.progressBar.BeginInvoke(
          (MethodInvoker)delegate() { this.progressBar.Style = ProgressBarStyle.Blocks; }
        );
      }

      // Send the new progress to the progress bar
      this.progressBar.AsyncSetValue(arguments.Progress);

    }

    /// <summary>
    ///   One-time timer callback that ensurs the form doesn't stay open when the
    ///   close request arrives at an inappropriate time.
    /// </summary>
    /// <param name="sender">Timer that has ticked</param>
    /// <param name="arguments">Not used</param>
    private void controlCreationTimerTicked(object sender, EventArgs arguments) {

      // This timer is intended to run only once to find out when the dialog has
      // been fully constructed and is running its message pump. So we'll disable
      // it as soon as it has been triggered once.
      this.controlCreationTimer.Enabled = false;

      // If the new state is 2, then the form was requested to close before it had
      // been fully constructed, so we should close it now!
      if(Interlocked.Increment(ref this.state) == 2) {
        Close();
      }

    }

    /// <summary>
    ///   Aborts the background operation when the user clicks the cancel button
    /// </summary>
    /// <param name="sender">Button that has been clicked</param>
    /// <param name="arguments">Not used</param>
    private void cancelClicked(object sender, EventArgs arguments) {

      if(this.abortReceiver != null) {

        // Do this first because the abort receiver might trigger the AsyncEnded()
        // event in the calling thread (us!) and thus destroy our window even in
        // the safe and synchronous UI thread :)
        this.cancelButton.Enabled = false;

        // Now we're ready to abort!
        this.abortReceiver.AsyncAbort();
        this.abortReceiver = null;

      }

    }

    /// <summary>Delegate for the asyncEnded() method</summary>
    private EventHandler asyncEndedDelegate;
    /// <summary>Delegate for the asyncProgressUpdated() method</summary>
    private EventHandler<ProgressReportEventArgs> asyncProgressChangedDelegate;
    /// <summary>Whether the form can be closed and should be closed</summary>
    /// <remarks>
    ///   0: Nothing happened yet
    ///   1: Ready to close or close requested
    ///   2: Ready to close and close requested, triggers close
    /// </remarks>
    private int state;
    /// <summary>Whether we're receiving progress updates from the transaction</summary>
    /// <remarks>
    ///   0: No progress updates have arrived so far
    ///   1: We have received at least one progress update from the transaction
    /// </remarks>
    private int areProgressUpdatesIncoming;
    /// <summary>
    ///   If set, reference to an object implementing IAbortable by which the
    ///   ongoing background process can be aborted.
    /// </summary>
    private IAbortable abortReceiver;

  }

} // namespace Nuclex.Windows.Forms

#endif // WITH_NUCLEX_SUPPORT_TRANSACTIONS