How to avoid canceling export when user use scroll wheel

[Act-3D]

I have simple custom exporter based on IExportContext.

When during exporting I use scroll wheel then exporting is canceled in the middle of proccess (in random place).

IsCanceled() method always return false.
No exception is throw.

Question:

How to avoid canceling export when user use scroll wheel?

[Act-3D]

Any news about this issue?

[jeremytammik]

Dear Artur,

Sorry for the late response.

Hmm. I have no news so far. I wonder how this can be communicated to the development team. I don't know how to reproduce this. Do I need any special equipment? I don't have a scroll wheel to test with. I have never heard anyone else reporting anything similar. Can you provide a reproducible case?

http://thebuildingcoder.typepad.com/blog/about-the-author.html#1b

Thank you!

Cheers,

Jeremy

[Act-3D]

Hi Jeremy,

Thank you for answer.

Steps to reproduce:

1. Take any custom exporter

(for example: http://thebuildingcoder.typepad.com/blog/2013/07/graphics-pipeline-custom-exporter.html#5)

2. Load any Revit project 

3. Go to {3D} view

4. Start export

5. During export use mouse wheel

[Act-3D]

Hi Jeremy,

Did you manage to reproduce the problem?

/Artur

[jeremytammik · Accepted solution]

Dear Artur,

Thank you for your update and renewed prompting.

Yes, I have reproduced the issue.

To do so, I migrated the sample you pointed out to Revit 2017 and posted it on GitHub:

https://github.com/jeremytammik/CustomExporterCollada

When I run the command and activate the mouse scroll wheel, an exception of type ExternalApplicationException is thrown from within the call to `exporter.Export(view3D)`, saying

  Object reference not set to an instance of an object.

I remember seeing the same exception being thrown once before.

It was reported in several comments by Helen Huang on

http://thebuildingcoder.typepad.com/blog/2013/07/adn-mesh-data-custom-exporter-to-json.html

I reported it to the development team in the database issue REVIT-94525 [API CustomExporter throws ExternalApplicationException after call to Finish].

This issue has been verified by the development team and classified as Code Fix Needed, submitting a new issue REVIT-100187 [API CustomExporter throws ExternalApplicationException after call to Finish].

That issue is still open.

I added a note of your report to it.

The case faced by Helen was easy to work around: simply add an exception handler around the call to `Finish`:

  try
  {
    exporter.Export( view );
  }
  catch( Autodesk.Revit.Exceptions.ExternalApplicationException ex )
  {
    Debug.Print( "ExternalApplicationException " + ex.Message );
  }

Here is the code for that case on GitHub:

https://github.com/jeremytammik/CustomExporterAdnMeshJson

Here is the fix I applied:

https://github.com/jeremytammik/CustomExporterAdnMeshJson/blob/master/CustomExporterAdnMeshJson/Comm...

I created a new GitHub repository for the sample you pointed to:

https://github.com/jeremytammik/CustomExporterCollada

It contains the code you point to in a solution for Revit 2017.

I added the same workaround to your code as well:

https://github.com/jeremytammik/CustomExporterCollada/commit/f734407aca033c42295e8748544d630ee51075c...

That seems to resolve the problem.

The fixed version is marked as release 2017.0.0.1:

https://github.com/jeremytammik/CustomExporterCollada/releases/tag/2017.0.0.1

I hope this helps.

Best regards,

Jeremy

[Act-3D]

Thank you Jeremy,

The another workaround I found is to disable of scroll wheel for the time of export.

[jeremytammik]

How do you disable the use of the scroll wheel for the time of export, please?

Thank you!

Cheers,

Jeremy

[Act-3D]

I used EnableWindow() function on view window.

The name of view window ("AfxFrameOrView140u") I found via Spy++.

Here is class I made. Tested on Revit 2017 so far.

 class RevitWindowUtility
    {
        [DllImport("user32.dll", SetLastError = true)]
        public static extern IntPtr FindWindowEx(IntPtr hwndParent, IntPtr hwndChildAfter, string lpszClass, string lpszWindow);

        [DllImport("user32.dll")]
        [return: MarshalAs(UnmanagedType.Bool)]
        static extern bool EnableWindow(IntPtr hWnd, bool bEnable);

        static IntPtr viewWindowHwnd = IntPtr.Zero;

        public static IntPtr FindChildWindow(IntPtr hwndParent, string lpszClass, string lpszTitle)
        {
            return FindChildWindow(hwndParent, IntPtr.Zero, lpszClass, lpszTitle);
        }

        public static IntPtr FindChildWindow(IntPtr hwndParent, IntPtr hwndChildAfter, string lpszClass, string lpszTitle)
        {
            IntPtr hwnd = FindWindowEx(hwndParent, IntPtr.Zero, lpszClass, lpszTitle);
            if (hwnd == IntPtr.Zero)
            {
                IntPtr hwndChild = FindWindowEx(hwndParent, IntPtr.Zero, null, null);
                while (hwndChild != IntPtr.Zero && hwnd == IntPtr.Zero)
                {
                    hwnd = FindChildWindow(hwndChild, IntPtr.Zero, lpszClass, lpszTitle);
                    if (hwnd == IntPtr.Zero)
                    {
                        hwndChild = FindWindowEx(hwndParent, hwndChild, null, null);
                    }
                }
            }
            return hwnd;
        }

        public static IntPtr GetRevitMainWindowHwnd()
        {
            Process process = Process.GetCurrentProcess();
            return process.MainWindowHandle;
        }

        public static void FindViewWindowHwnd()
        {
            IntPtr mainWindowHwnd = GetRevitMainWindowHwnd();
            viewWindowHwnd = FindChildWindow(mainWindowHwnd, IntPtr.Zero, "AfxFrameOrView140u", null);
        }

        public static void EnableViewWindow(bool enable)
        {
            if (viewWindowHwnd == IntPtr.Zero)
            {
                FindViewWindowHwnd();
            }

            if (viewWindowHwnd != IntPtr.Zero)
                EnableWindow(viewWindowHwnd, enable);
        }

[jeremytammik]

Dear Artur,

Thank you for your super cool sample code snippet.

I hope others can find lots of interesting uses for this direct access to the view window.

Long live Spy++!

Cheers,

Jeremy