starred/terminal
1
0
Fork 0
mirror of https://github.com/microsoft/terminal.git synced 2026-02-04 05:35:20 +00:00
Code Issues 19.0k Packages Projects Releases 20 Wiki Activity

[PR #14936] Ensure that delayed EOL wrap is reset when necessary #30316

New Issue
Open
opened 2026-01-31 09:40:02 +00:00 by claunia · 0 comments
claunia commented 2026-01-31 09:40:02 +00:00
Owner
Copy Link

Original Pull Request: https://github.com/microsoft/terminal/pull/14936

State: closed
Merged: Yes

When a character is written in the last column of a row, the cursor
doesn't move, but instead sets a "delayed EOL wrap" flag. If another
character is then output while that flag is still set, the cursor moves
to the start of the next line, before writing to the buffer.

That flag is supposed to be reset when certain control sequences are
executed, but prior to now we haven't always handled that correctly.
With this PR, we should be resetting the flag appropriately in all the
places that it's expected to be reset.

For the most part, I'm following the DEC STD 070 reference, which lists
a bunch of operations that are intended to reset the delayed wrap flag:

DECSTBM, DECSWL, DECDWL, DECDHL, setting DECCOLM and DECOM,
resetting DECCOLM, DECOM, and DECAWM, CUU, CUD, CUF, CUB,
CUP, HVP, BS, LF, VT, FF, CR, IND, RI, NEL, ECH,
DCH, ICH, EL, DECSEL, DL, IL, ED, and DECSED.

We were already resetting the flag for any of the operations that
performed cursor movement, since that always triggers a reset for us.
However, I've now also added manual resets in those ops that weren't
moving the cursor.

Horizontal tabs are a special case, though. Technically the standard
says they should reset the flag, but most DEC terminals never followed
that rule, and most modern terminals agree that it's best for a tab to
leave the flag as it is. Our implementation now does that too.

But as mentioned above, we automatically reset the flag on any cursor
movement, so the tab operation had to be handled as a special case,
saving and restoring the flag when the cursor is updated.

Another flaw in our implementation was that we should have been saving
and restoring the flag as part of the cursor state in the DECSC and
DECRC operations. That's now been fixed in this PR too.

I should also mention there was a change I had to make to the conpty
renderer, because it was sometimes using an EL sequence while the
terminal was in the delayed EOL wrap state. This would reset the flag,
and break subsequent output, so I've now added a check to prevent that
from happening.

Validation Steps Performed

I've added some unit tests that confirm the operations listed above are
now resetting the delayed EOL wrap as expected, and I've expanded the
existing CursorSaveRestore test to make sure the flag is being saved
and restored correctly.

I've also manually confirmed that the test case in issue #3177 now
matches XTerm's output, and I've confirmed that the results of the
wraptest script1 now match XTerm's results.

Closes #3177

**Original Pull Request:** https://github.com/microsoft/terminal/pull/14936 **State:** closed **Merged:** Yes --- When a character is written in the last column of a row, the cursor doesn't move, but instead sets a "delayed EOL wrap" flag. If another character is then output while that flag is still set, the cursor moves to the start of the next line, before writing to the buffer. That flag is supposed to be reset when certain control sequences are executed, but prior to now we haven't always handled that correctly. With this PR, we should be resetting the flag appropriately in all the places that it's expected to be reset. For the most part, I'm following the DEC STD 070 reference, which lists a bunch of operations that are intended to reset the delayed wrap flag: `DECSTBM`, `DECSWL`, `DECDWL`, `DECDHL`, setting `DECCOLM` and `DECOM`, resetting `DECCOLM`, `DECOM`, and `DECAWM`, `CUU`, `CUD`, `CUF`, `CUB`, `CUP`, `HVP`, `BS`, `LF`, `VT`, `FF`, `CR`, `IND`, `RI`, `NEL`, `ECH`, `DCH`, `ICH`, `EL`, `DECSEL`, `DL`, `IL`, `ED`, and `DECSED`. We were already resetting the flag for any of the operations that performed cursor movement, since that always triggers a reset for us. However, I've now also added manual resets in those ops that weren't moving the cursor. Horizontal tabs are a special case, though. Technically the standard says they should reset the flag, but most DEC terminals never followed that rule, and most modern terminals agree that it's best for a tab to leave the flag as it is. Our implementation now does that too. But as mentioned above, we automatically reset the flag on any cursor movement, so the tab operation had to be handled as a special case, saving and restoring the flag when the cursor is updated. Another flaw in our implementation was that we should have been saving and restoring the flag as part of the cursor state in the `DECSC` and `DECRC` operations. That's now been fixed in this PR too. I should also mention there was a change I had to make to the conpty renderer, because it was sometimes using an `EL` sequence while the terminal was in the delayed EOL wrap state. This would reset the flag, and break subsequent output, so I've now added a check to prevent that from happening. ## Validation Steps Performed I've added some unit tests that confirm the operations listed above are now resetting the delayed EOL wrap as expected, and I've expanded the existing `CursorSaveRestore` test to make sure the flag is being saved and restored correctly. I've also manually confirmed that the test case in issue #3177 now matches XTerm's output, and I've confirmed that the results of the wraptest script[^1] now match XTerm's results. [^1]: https://github.com/mattiase/wraptest/ Closes #3177
claunia added the pull-request label 2026-01-31 09:40:02 +00:00
Sign in to join this conversation.
No Branch/Tag Specified
Branches Tags
Labels
Clear labels
⛺ Reserved
A11yCO
A11yMAS
A11ySev1
A11ySev2
A11ySev3
A11yTTValidated
A11yUsable
A11yVoiceAccess
A11yWCAG
Area-Accessibility
Area-AtlasEngine
Area-AzureShell
Area-Build
Area-Build
Area-Chat
Area-CmdPal
Area-CodeHealth
Area-Commandline
Area-CookedRead
Area-DefApp
Area-Extensibility
Area-Fonts
Area-GroupPolicy
Area-i18n
Area-Input
Area-Interaction
Area-Interop
Area-Localization
Area-Output
Area-Performance
Area-Portable
Area-Quality
Area-Remoting
Area-Rendering
Area-Schema
Area-Server
Area-Settings
Area-SettingsUI
Area-ShellExtension
Area-ShellExtension
Area-ShellExtension
Area-Suggestions
Area-Suggestions
Area-TerminalConnection
Area-TerminalControl
Area-Theming
Area-UserInterface
Area-VT
Area-Windowing
Area-WPFControl
AutoMerge
Blocking-Ingestion
Culprit-Centennial
Culprit-WinUI
Disability-All
Disability-Blind
Disability-LowVision
Disability-Mobility
External-Blocked-WinUI3
Fixed
Gathering-Data
good first issue
HCL-E+D
HCL-WindowsTerminal
Help Wanted
Impact-Compatibility
Impact-Compliance
Impact-Correctness
Impact-Visual
In-PR
InclusionBacklog
InclusionBacklog-Windows TerminalWin32
InclusionCommitted-202206
Issue-Bug
Issue-Docs
Issue-Feature
Issue-Feature
Issue-Question
Issue-Samples
Issue-Scenario
Issue-Task
Needs-Attention
Needs-Author-Feedback
Needs-Bisect
Needs-Discussion
Needs-Repro
Needs-Tag-Fix
Needs-Tag-Fix
Needs-Triage
No-Recent-Activity
Priority-0
Priority-1
Priority-2
Priority-3
Product-Cmd.exe
Product-Colortool
Product-Colortool
Product-Colortool
Product-Conhost
Product-Conpty
Product-Meta
Product-Powershell
Product-Terminal
Product-WSL
pull-request
Mirrored from GitHub Pull Request
 Resolution-Answered
Resolution-By-Design
Resolution-Duplicate
Resolution-External
Resolution-Fix-Available
Resolution-Fix-Committed
Resolution-No-Repro
Resolution-Won't-Fix
Severity-Blocking
Severity-Crash
Severity-DataLoss
spam
this-will-be-a-breaking-change
Tracking-External
WindowsTerminal_Win32
Work-Item
zAskModeBug
zInbox-Bug
No Label pull-request
Milestone
No items
No Milestone
Projects
Clear projects
No project
Assignees
Clear assignees
claunia
No Assignees
1 Participants
Notifications
Due Date
No due date set.
Dependencies

No dependencies set.

Reference: starred/terminal#30316
Delete Branch "%!s()"

Deleting a branch is permanent. Although the deleted branch may continue to exist for a short time before it actually gets removed, it CANNOT be undone in most cases. Continue?