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[PR #5870] Fix an accidental regression from #5771 #26524

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opened 2026-01-31 09:16:34 +00:00 by claunia · 0 comments
claunia commented 2026-01-31 09:16:34 +00:00
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Original Pull Request: https://github.com/microsoft/terminal/pull/5870

State: closed
Merged: Yes

This PR reverts a relatively minor change that was made incorrectly to
ConPTY in #5771.

In that PR, I authored two tests. One of them actually caught the bug
that was supposed to be fixed by #5771. The other test was simply
authored during the investigation. I believed at the time that the test
revealed a bug in conpty that was fixed by removing this block of
code. However, an investigation itno #5839 revealed that this code was
actually fairly critical.

So, I'm also skipping this buggy test for now. I'm also adding a
specific test case to this bug.

The problem in the bugged case of WrapNewLineAtBottom is that
WriteCharsLegacy is wrapping the bottom row of the ConPTY buffer,
which is causing the cursor to automatically move to the next line in
the buffer. This is because WriteCharsLegacy isn't being called with
the WC_DELAY_EOL_WRAP flag. So, in that test case,

  • The client emits a wrapped line to conpty
  • conpty fills the bottom line with that text, then dutifully increments
    the buffer to make space for the cursor on a new bottom line.
  • Conpty reprints the last ~ of the wrapped line
  • Then it gets to the next line, which is being painted before the
    client emits the rest of the line of text to fill that row.
  • Conpty thinks this row is empty, (it is) and manually breaks the row.

However, the test expects this row to be emitted as wrapped. The problem
comes from the torn state in the middle of these frames - the original
line probably should remain wrapped, but this is a sufficiently rare
case that the fix is being punted into the next release.

It's possible that improving how we handle line wrapping might also fix
this case - currently we're only marking a row as wrapped when we print
the last cell of a row, but we should probably mark it as wrapped
instead when we print the first char of the following row. That work
is being tracked in #5800

The real bug in this PR

The problem in the DeleteWrappedWord test is that the first line is
still being marked as wrapped. So when we get to painting the line below
it, we'll see that there are no characters to be printed (only spaces),
we emit a ^[20X^[20C, but the cursor is still at the end of the first
line. Because it's there, we don't actually clear the text we want to
clear.

So DeleteWrappedWord, #5839 needs the _wrappedRow = std::nullopt;
statement here.

References

  • I guess just look at #5800, I put everything in there.

Validation Steps Performed

  • Tested manually that this was fixed for the Terminal
  • ran tests

Closes #5839

**Original Pull Request:** https://github.com/microsoft/terminal/pull/5870 **State:** closed **Merged:** Yes --- This PR reverts a relatively minor change that was made incorrectly to ConPTY in #5771. In that PR, I authored two tests. One of them actually caught the bug that was supposed to be fixed by #5771. The other test was simply authored during the investigation. I believed at the time that the test revealed a bug in conpty that was fixed by _removing_ this block of code. However, an investigation itno #5839 revealed that this code was actually fairly critical. So, I'm also _skipping_ this buggy test for now. I'm also adding a specific test case to this bug. The problem in the bugged case of `WrapNewLineAtBottom` is that `WriteCharsLegacy` is wrapping the bottom row of the ConPTY buffer, which is causing the cursor to automatically move to the next line in the buffer. This is because `WriteCharsLegacy` isn't being called with the `WC_DELAY_EOL_WRAP` flag. So, in that test case, * The client emits a wrapped line to conpty * conpty fills the bottom line with that text, then dutifully increments the buffer to make space for the cursor on a _new_ bottom line. * Conpty reprints the last `~` of the wrapped line * Then it gets to the next line, which is being painted _before_ the client emits the rest of the line of text to fill that row. * Conpty thinks this row is empty, (it is) and manually breaks the row. However, the test expects this row to be emitted as wrapped. The problem comes from the torn state in the middle of these frames - the original line probably _should_ remain wrapped, but this is a sufficiently rare case that the fix is being punted into the next release. It's possible that improving how we handle line wrapping might also fix this case - currently we're only marking a row as wrapped when we print the last cell of a row, but we should probably mark it as wrapped instead when we print the first char of the _following_ row. That work is being tracked in #5800 ### The real bug in this PR The problem in the `DeleteWrappedWord` test is that the first line is still being marked as wrapped. So when we get to painting the line below it, we'll see that there are no characters to be printed (only spaces), we emit a `^[20X^[20C`, but the cursor is still at the end of the first line. Because it's there, we don't actually clear the text we want to clear. So DeleteWrappedWord, #5839 needs the `_wrappedRow = std::nullopt;` statement here. ## References * I guess just look at #5800, I put everything in there. ## Validation Steps Performed * Tested manually that this was fixed for the Terminal * ran tests Closes #5839
claunia added the pull-request label 2026-01-31 09:16:34 +00:00
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Reference: starred/terminal#26524
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