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braille display line wrap algorithm assumes one cell less than is present on display #18016

@RoryMichie

Description

@RoryMichie

Steps to reproduce:

  1. enter a document (tested in notepad)
  2. write a line of great than or equal to [display-num-of-chars] characters (in my case, 40 with an APH Mantis Q40, but have also tested this on a BrailleNote Touch Plus with 32), in such a way that one of the words ought to end on the last cell of the display.
  3. observe unexpected behaviours as described

Actual behavior:

(the Braille Viewer is not easily letting me copy out of it. I will investigate this further and comment with Braille Viewer output, but in lieu of that output I will endeavour to describe this issue to the very best of my abilities for now).
(presuming one is on a 40 cell braille display and that the Braille table is set to Unified English Braille)
The following line:

There is something I really need to say, but I cannot bring myself to say it. I never can.

is displayed in two Braille lines, the first of which has three blank cells at the end

Expected behavior:

The first line should end on the word "cannot" (dots 456, dots 14) and thus optimally use all the available space on the display.
Contrastingly this similar line:

There's something I really need to say, but I cannot bring myself to say it. I never can

is displayed in two lines as well, the 39th cell being dots 14 to end the word "cannot", and the last cell left blank as expected.

NVDA logs, crash dumps and other attachments:

log attached to issue

nvda log 26 april 2025.txt

System configuration

NVDA installed/portable/running from source:

installed (downloaded from nvaccess.org)

NVDA version:

2024.4.2 (2024.4.2.35031)

Windows version:

Windows 11 24H2 (AMD64) build 26100.3775

Name and version of other software in use when reproducing the issue:

Notepad.

Other information about your system:

Other questions

Does the issue still occur after restarting your computer?

Yes.

Have you tried any other versions of NVDA? If so, please report their behaviors.

No.

If NVDA add-ons are disabled, is your problem still occurring?

Yes, The problem still occurs with addons disabled.

Does the issue still occur after you run the COM Registration Fixing Tool in NVDA's tools menu?

Yes, the problem still occurs after running the COM registration fixing tool.

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    component/braillep3https://github.com/nvaccess/nvda/blob/master/projectDocs/issues/triage.md#prioritytriagedHas been triaged, issue is waiting for implementation.

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