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Unhandled Exception / List index out of range error pressing bumper keys on Freedom Scientific Focus 80 Blue Braille display #8849

Qchristensen opened this issue Oct 17, 2018 · 5 comments


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@Qchristensen Qchristensen commented Oct 17, 2018

Steps to reproduce:

(Issue reported by a client via email. Log attached)
nvda (9).log

  1. Open notepad with text which stretches over a line.
  2. Press the right bumper bar down to scroll forward through text.

Actual behavior:

Exception generated, front panel keys on display stop working.
Additional text not read.

Expected behavior:

Display should scroll to read additional text.

System configuration:

Windows 7, 32 Bit with SP1.

NVDA Installed/portable/running from source:

NVDA 2018.3.2 installed. No add-ons, and using the Freedom Scientific display driver recommended in the NVDA User Guide:

Does the issue still occur after restarting your PC?


Have you tried any other versions of NVDA?

Yes, this issue has been present "for several years".

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@bramd bramd commented Oct 17, 2018

@Qchristensen Thanks for the bug report. Could you please try this NVDA build:

I recently did a rewrite of the Freedom Scientific driver and I hope the issue is fixed in this driver. If not, could you please submit a new log so I can fix this before the new driver lands in NVDA? By the way, the linked build is not signed and might give a warning on opening it. I recommend to use this build only for testing purposes and not to install it.


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@howardgld howardgld commented Oct 18, 2018

I tested with your build and while there are no more unhandled exceptions the problem is not really solved. Now when I press RightBumperBarDown nothing happens except that I get an odd tone. The front panel keys no longer lock up so that's an improvement.

I think that we're really looking at the wrong issue here. What seems to be happening in your build as well as in the released version is that NVDA is misinterpreting all bumper bar presses. They seem to be off by one. When the attached log was generated, I pressed LeftBumperBarUp, LeftBumperBarDown, RightBumperBarUp and RightBumperBarDown in that order. The log shows inputs of LeftBumperBarDown, RightBumperBarUp, RightBumperBarDown and then an error presumably from an unrecognized, out-of-range input. It's only the bumper bars that have this problem; all other keys are OK. Also, the Braille display works correctly with JAWS where I use the bumper pbars quite a bit.



bramd added a commit to bramd/nvda that referenced this issue Oct 21, 2018
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@bramd bramd commented Oct 21, 2018

@howardgld Yes, I think the list mapping key codes to names was missing an empty value, which made all bumper keys (at the end of this list) off by one. I don't have a model with bumper keys to test, could you please give this build a try:


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@howardgld howardgld commented Oct 22, 2018

I'm happy to report that the bumper keys work correctly with this new build. I'm looking forward to seeing this fix in the next release. Thanks very much!


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@howardgld howardgld commented Mar 3, 2019

I don't like to nag but Bramd fixed my issue in October but the fix hasn't made it to the released version yet. Properly working bumper keys would make my life a lot easier. Would love to see this in 2019.1 -- if not the whole new Focus driver then at least the key table fix for the bumper keys.



@nvaccessAuto nvaccessAuto added this to the 2019.2 milestone May 21, 2019
feerrenrut added a commit that referenced this issue May 21, 2019
Braille output and wizWheels are working. Tested on a Focus 40 blue

Freedom Scientific braille displays are now supported by braille display auto detection (#7727)
When an auto detected braille display is connected via Bluetooth, NVDA will keep searching for USB displays supported by the same driver and switch to a USB connection if it becomes available

The bumper keys now work correctly on Freedom Scientific braille displays (#8849)

Co-Authored-By: Leonard de Ruijter <>

fixes #7727
fixes #4464
fixes #8849
fixes #8729
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5 participants