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UIA: GetVisibleRanges() returning text beyond the visible range #10855

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opened 2026-01-31 02:32:03 +00:00 by claunia · 6 comments
claunia commented 2026-01-31 02:32:03 +00:00
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Originally created by @codeofdusk on GitHub (Oct 2, 2020).

Originally assigned to: @carlos-zamora on GitHub.

Environment

Windows build number: [run `[Environment]::OSVersion` for powershell, or `ver` for cmd] OpenConsole (relaese build of #7792 )
Windows Terminal version (if applicable):

Any other software? NVDA

Steps to reproduce

  1. Call GetVisibleRanges.
  2. Make a degenerate range at the end of this range.
  3. Expand the degenerate range to line.

Expected behaviour

The last visible line is contained in the range.

Actual behaviour

An empty line is contained in the range.

Originally created by @codeofdusk on GitHub (Oct 2, 2020). Originally assigned to: @carlos-zamora on GitHub. <!-- 🚨🚨🚨🚨🚨🚨🚨🚨🚨🚨 I ACKNOWLEDGE THE FOLLOWING BEFORE PROCEEDING: 1. If I delete this entire template and go my own path, the core team may close my issue without further explanation or engagement. 2. If I list multiple bugs/concerns in this one issue, the core team may close my issue without further explanation or engagement. 3. If I write an issue that has many duplicates, the core team may close my issue without further explanation or engagement (and without necessarily spending time to find the exact duplicate ID number). 4. If I leave the title incomplete when filing the issue, the core team may close my issue without further explanation or engagement. 5. If I file something completely blank in the body, the core team may close my issue without further explanation or engagement. All good? Then proceed! --> <!-- This bug tracker is monitored by Windows Terminal development team and other technical folks. **Important: When reporting BSODs or security issues, DO NOT attach memory dumps, logs, or traces to Github issues**. Instead, send dumps/traces to secure@microsoft.com, referencing this GitHub issue. If this is an application crash, please also provide a Feedback Hub submission link so we can find your diagnostic data on the backend. Use the category "Apps > Windows Terminal (Preview)" and choose "Share My Feedback" after submission to get the link. Please use this form and describe your issue, concisely but precisely, with as much detail as possible. --> # Environment ```none Windows build number: [run `[Environment]::OSVersion` for powershell, or `ver` for cmd] OpenConsole (relaese build of #7792 ) Windows Terminal version (if applicable): Any other software? NVDA ``` # Steps to reproduce 1. Call `GetVisibleRanges`. 2. Make a degenerate range at the end of this range. 3. Expand the degenerate range to line. <!-- A description of how to trigger this bug. --> # Expected behaviour The last visible line is contained in the range. <!-- A description of what you're expecting, possibly containing screenshots or reference material. --> # Actual behaviour An empty line is contained in the range. <!-- What's actually happening? -->
claunia added the Product-ConhostNeeds-TriageIssue-BugArea-Accessibility labels 2026-01-31 02:32:03 +00:00
claunia commented 2026-01-31 02:32:05 +00:00
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@codeofdusk commented on GitHub (Oct 2, 2020):

Cc @carlos-zamora.

@codeofdusk commented on GitHub (Oct 2, 2020): Cc @carlos-zamora.
claunia commented 2026-01-31 02:32:05 +00:00
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@carlos-zamora commented on GitHub (Oct 2, 2020):

Root Cause

UiaTextRanges (UTR) are { inclusive start, exclusive end }. To encompass the first line of the buffer, an UTR would be { (0,0), (0,1) }.

GetVisibleRanges returns the UTR encompassing the viewport.

Creating a degenerate range at the end of the visible viewport means that we have a degenerate range underneath the viewport. This is because the exclusive end is {0, viewport.Height()+1}.

Expanding by line makes you encompass the line that _start is currently on. Since _start = _end, and _end is on the line under the viewport, you encompass the line under the viewport.

The fix is simple: if we have a degenerate range, and we try to expand by line, move _start up instead of _end down.

@DHowett This can be added into https://github.com/microsoft/terminal/pull/7792, if so desired. It would make a minor modification to the "expand by line" change I made, but I would want to add a test that specifically covers these repro steps. It's also small enough that we can make this a separate PR. I'm fine either way. Risk is minor since we would only do this when it's a degenerate range.

@carlos-zamora commented on GitHub (Oct 2, 2020): ### Root Cause UiaTextRanges (UTR) are { inclusive start, exclusive end }. To encompass the first line of the buffer, an UTR would be { (0,0), (0,1) }. `GetVisibleRanges` returns the UTR encompassing the viewport. Creating a degenerate range at the end of the visible viewport means that we have a degenerate range _underneath the viewport_. This is because the exclusive end is {0, viewport.Height()+1}. Expanding by line makes you encompass the line that _start is currently on. Since _start = _end, and _end is on the line under the viewport, you encompass the line under the viewport. **The fix is simple**: if we have a degenerate range, and we try to expand by line, move _start up instead of _end down. @DHowett This can be added into https://github.com/microsoft/terminal/pull/7792, if so desired. It would make a minor modification to the "expand by line" change I made, but I would want to add a test that specifically covers these repro steps. It's also small enough that we can make this a separate PR. I'm fine either way. Risk is minor since we would only do this when it's a degenerate range.
claunia commented 2026-01-31 02:32:05 +00:00
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@codeofdusk commented on GitHub (Oct 2, 2020):

I think this will also fix #5481 (which is also separately fixed by nvaccess/nvda#11639).

@codeofdusk commented on GitHub (Oct 2, 2020): I think this will also fix #5481 (which is also separately fixed by nvaccess/nvda#11639).
claunia commented 2026-01-31 02:32:05 +00:00
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@DHowett commented on GitHub (Oct 2, 2020):

Separate PR plz

@DHowett commented on GitHub (Oct 2, 2020): Separate PR plz
claunia commented 2026-01-31 02:32:05 +00:00
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@carlos-zamora commented on GitHub (Oct 2, 2020):

So, I attempted to fix this on dev/cazamor/a11y/expand-line-under-viewport. That definitely fixes the bug, but I don't think it's the correct behavior overall. I've summarized in the collapsible section below some concerns with the implementation.

Concerns with my branch My branch makes it such that a degenerate range at the beginning of a line expands backwards, instead of forwards. Being in the state described in this bug report (degenerate range at the end of the visible ranges) satisfies this case. When you expand by character/line, you now get the last character/line of the visible range. So the bug is fixed.

However, this would introduce another bug/discrepancy. Consider a line being encompassed in a range. Then you move "end" to "start". When you expand by line, I expect the current line to be covered. Instead, it'll cover the previous line. So the question is, when would we distinguish between wanting to expand forwards vs backwards?

It sounds like UIA may be implemented properly for this scenario, and NVDA would have to do the extra work here by moving to the previous character, then expanding by line.

In MS Word, if you have a few paragraphs of text (=lorem(5,5))...

  • Expand by paragraph
  • move start to end
  • NOTE: you are now at the beginning of the next paragraph
  • expand by line
  • NOTE: you now have a range of the first line of the next paragraph

ConHost doesn't have paragraph support, but we can kind of equate getting the visible ranges to getting a paragraph in MS Word (because it's a range that expands multiple lines). If that's the case, the current behavior is correct.

@carlos-zamora commented on GitHub (Oct 2, 2020): So, I attempted to fix this on `dev/cazamor/a11y/expand-line-under-viewport`. That definitely fixes the bug, but I don't think it's the correct behavior overall. I've summarized in the collapsible section below some concerns with the implementation. <details> <summary>Concerns with my branch</summary> My branch makes it such that a degenerate range at the beginning of a line expands backwards, instead of forwards. Being in the state described in this bug report (degenerate range at the end of the visible ranges) satisfies this case. When you expand by character/line, you now get the last character/line of the visible range. So the bug is fixed. However, this would introduce another bug/discrepancy. Consider a line being encompassed in a range. Then you move "end" to "start". When you expand by line, I expect the current line to be covered. Instead, it'll cover the previous line. So the question is, when would we distinguish between wanting to expand forwards vs backwards? It sounds like UIA may be implemented properly for this scenario, and NVDA would have to do the extra work here by moving to the previous character, then expanding by line. </details> In MS Word, if you have a few paragraphs of text (`=lorem(5,5)`)... - Expand by paragraph - move start to end - NOTE: you are now at the beginning of the next paragraph - expand by line - NOTE: you now have a range of the first line of the next paragraph ConHost doesn't have paragraph support, but we can kind of equate getting the visible ranges to getting a paragraph in MS Word (because it's a range that expands multiple lines). If that's the case, the current behavior is correct.
claunia commented 2026-01-31 02:32:06 +00:00
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@codeofdusk commented on GitHub (Oct 2, 2020):

These seem to be NVDA issues. See nvaccess/nvda#11722.

@codeofdusk commented on GitHub (Oct 2, 2020): These seem to be NVDA issues. See nvaccess/nvda#11722.
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