Visual Studio 2010 Professional - LookupError: No such position

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Reported by ianr on 2011-02-18 17:51
Sometimes when switching documents with ctrl + tab or when in the solution explorer and hitting enter to open a document NVDA starts making the error noise repeatedly.
Alt tabbing away from the application and back will stop NVDA from making the error noise. Otherwise it usually does not stop making the error noise.

In the nvda log this error shows up repeatedly:
LookupError: No such position

I have attached the nvda log to this ticket.

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Attachment nvda lookup error.log added by ianr on 2011-02-18 17:53
Description:
nvda lookup error log

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Attachment nvda debug lookup error.log added by ianr on 2011-02-19 21:51
Description:
A snippet from an nvda log that shows the same error, this one had debug log level set instead of info

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Comment 1 by jteh on 2011-02-21 03:40
This issue is related to braille. I'm not really sure why this happens yet and it's going to be tricky to debug without me having access to the software.

When this happens, what do you see on your braille display?
Changes:
Milestone changed from None to 2011.2

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Attachment nvda braille error.log added by ianr on 2011-02-21 19:48
Description:
NVDA log with log level at debug and com error inside

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Comment 2 by ianr on 2011-02-21 19:54
I am using a HumanWare Brailliant 80 with the native nvda Baum/HumanWare/APH braille displays driver. Though I used to get the same behavior back when I used BRLTTY but I can't say for sure if it was the exact same error in the log.

As for not having the software this problem may occur in the Visual Studio 2010 Express Edition which is free. That might be worth a try.

I also attached a new file which gives the same symptoms (error noise while working in Visual Studio) but that shows a com error instead. Looking at the stacktrace braille.pyo is mentioned so it is probably closely related to the lookup error.

I will find out what shows on my braille display when these errors occur and get back to you.

Thanks for looking into this.

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Comment 3 by ianr on 2011-02-21 20:01
I just received the "lookup error" again and checked my braille display this time.

The braille display has all pins down, so no pins are raised. Not even pins for displaying the current location of the cursor.

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Comment 4 by jteh on 2011-05-31 11:08
How often do you see this? Would you be happy to test with a special build to debug this? Looking through the code, I can't figure out how this is happening.

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Comment 5 by ianr on 2011-06-01 16:54
I am definitely happy to test with a special build. But it seems that this error is not occurring any more.

I was not using Visual Studio for about a month, when I came back to it I did install the newly released Service Pack 1 for Visual Studio and in the meantime had upgraded to the full release of nvda 2011.1.
It is possible that one of these fixed the issue.

I am happy to call this closed. Thanks for looking into it.

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Comment 6 by ianr on 2011-06-01 21:42
It seems I spoke too soon.

Though I am no longer getting the error sound when the look up error occurs it is still happening.
My braille display sometimes lowers all pins while in Visual Studio, this time I checked the log after it happened and there were several of the lookup errors in a row.

I'd still be happy to test with a special build and give feedback.

Why do I not hear the error noise anymore?

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Comment 7 by jteh on 2011-06-01 21:53
The error noise is suppressed in rc and stable releases, as it usually doesn't affect the user.

How often does this happen? Also, when it does, what happens if you press scroll back on your braille display? What happens if you press NVDA+upArrow?

Your log shows you pressing down arrow in the document before the problem occurred, not enter or ctrl+tab as noted in the description. Is there something we're missing in terms of steps to reproduce?

I'm almost certain that this is due to a bug in Visual Studio, as it seems we're being told there is no text when there in fact is. Nevertheless, NVDA should cope with this gracefully, though the "all pins down" issue you're seeing won't be fixed even if we can handle this case in NVDA.

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Comment 8 by ianr on 2011-06-02 17:05
This happens maybe 5 to 10 times a day.

I used to notice it a lot more when the error noise occurred.

There is not a consistent way to reproduce it, I've noticed in the past when pressing control + tab to switch between documents and sometimes just when I am navigating around the text editor using the arrow keys. But it does not always happen when doing these actions, just sometimes.

alt tabbing away from visual studio and back will always fix it.
Even when the pins all become lowered NVDA will continue to read the text via speech.

When it happened this time I pressed the scroll up braille display key but nothing happened.
I pressed nvda + up and nvda read the current line, I press up and down arrow keys and the speech from nvda reads the lines correctly but the braille displays pins remain lowered.

Since nvda still reads the lines correctly it would seem it is still receiving text from visual studio correctly, but something has messed up it's interaction with the braille display and for some reason it only gets fixed once I move to another application.

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Comment 9 by jteh on 2011-06-06 11:19
Okay. After hours of mind-boggling, I finally thought of some scenarios where the braille code might hit this problem. I've fixed them in 8a4670d. I can't be certain that this fix will work for this particular case, as I still can't test with the actual software, though I'm hoping it works.

It'd be great if you could test with a snapshot containing this revision when it becomes available to see if this is fixed for you. Thanks.

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Comment 10 by ianr on 2011-06-07 22:07
I would be glad to test with the new version when it becomes available. I've been checking for it but it has not shown up on the snapshots page yet.

I am going to attach a log of an NVDA crash. I'm not sure that the crash is caused by the lookup error, it seems like that error does not cause a crash but it happens to be the last error message in the crash log so I'm not sure where else I should put it.

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Attachment nvda crash.log added by ianr on 2011-06-07 22:22
Description:

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Comment 11 by jteh on 2011-06-08 05:39
As I write this, latest available main snapshot is 4408. If you can't see it, you need to refresh the page.

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Comment 12 by briang1 on 2011-06-08 07:25
If you use the snap downloader it downloads, but the rest of the site seems to be giving errors at the moment here.

Internal Server Error
The server encountered an internal error or misconfiguration and was unable to complete your request.
Please contact the server administrator, sysadmin@nvaccess.org and inform them of the time the error occurred, and anything you might have done that may have caused the error.
More information about this error may be available in the server error log.
Additionally, a 500 Internal Server Error error was encountered while trying to use an ErrorDocument to handle the request.

Apache/2.2.17 (Ubuntu) Server at www.nvda-project.org Port 80

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Comment 13 by ianr on 2011-06-17 20:31
I've been using snapshot 4412 for a few days now and have not seen the lookup error issue. It looks like your changes fixed it. This particular snapshot seems to be a bit more stable for me than 2011.1 as well.

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Comment 14 by jteh on 2011-06-18 06:31
Changes:
State: closed