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 #15930] COOKED_READ_DATA: Fix scrolling under ConPTY #30782

New Issue
Open
opened 2026-01-31 09:42:54 +00:00 by claunia · 0 comments
claunia commented 2026-01-31 09:42:54 +00:00
Owner
Copy Link

Original Pull Request: https://github.com/microsoft/terminal/pull/15930

State: closed
Merged: Yes

This commit fixes 3 bugs:

  • COOKED_READ_DATA failed to initialize its _distanceCursor and
    _distanceEnd members. I took this as an opportunity to make them
    ptrdiff_t, to reduce the likelihood of overflows in the future.
  • COOKED_READ_DATA::_writeChars added scrollY to the written
    distance, even though WriteCharsLegacy writes a negative value into
    that out parameter. This was fixed by changing WriteCharsLegacy to
    write positive values and by adding a debug assertion.
  • StreamScrollRegion calls IncrementCircularBuffer which causes a
    synchronous (!) ConPTY flush to the output pipe (side note: this is
    the primary reason why newlines are so slow in ConPTY).
    Since cooked reads are supposed to behave like a pager and not write
    into the scrollback, we temporarily mark the buffer as inactive
    which prevents TextBuffer from snitching about it to VtEngine.

Even after this change, there's still some weird behavior left:

  • You cannot move your cursor back beyond (0,0), because this isn't a
    real pager-like implementation. That might be a neat future extension.
  • Writing a lot of text and pressing Ctrl+C doesn't properly place the
    cursor and scroll the buffer, unless the cursor is at the end.
    That might also be worth investigating in the future (minor issue).
  • When the viewport is full, backspacing more than 1 line of text
    (using Ctrl+Backspace) doesn't erase all of the affected lines,
    because COOKED_READ_DATA::_erase uses the same WriteCharsLegacy
    function to write whitespace to erase that text. It's only gone
    after typing one more character.
    I've written the code to mostly fix this, but decided against it
    as I considered the problem to be too niche to warrant extra code.

Closes #15899

Validation Steps Performed

  • Generate some text to paste in PowerShell: 
    "" + (0..512 | % { "word" + $_.ToString().PadLeft(4, "0") })
  • Launch cmd.exe and paste that text
  • No flickering ✅
  • No writing into the scrollback ✅
  • No weird behavior when backspacing ✅
**Original Pull Request:** https://github.com/microsoft/terminal/pull/15930 **State:** closed **Merged:** Yes --- This commit fixes 3 bugs: * `COOKED_READ_DATA` failed to initialize its `_distanceCursor` and `_distanceEnd` members. I took this as an opportunity to make them `ptrdiff_t`, to reduce the likelihood of overflows in the future. * `COOKED_READ_DATA::_writeChars` added `scrollY` to the written distance, even though `WriteCharsLegacy` writes a negative value into that out parameter. This was fixed by changing `WriteCharsLegacy` to write positive values and by adding a debug assertion. * `StreamScrollRegion` calls `IncrementCircularBuffer` which causes a synchronous (!) ConPTY flush to the output pipe (side note: this is the primary reason why newlines are so slow in ConPTY). Since cooked reads are supposed to behave like a pager and not write into the scrollback, we temporarily mark the buffer as inactive which prevents `TextBuffer` from snitching about it to VtEngine. Even after this change, there's still some weird behavior left: * You cannot move your cursor back beyond (0,0), because this isn't a real pager-like implementation. That might be a neat future extension. * Writing a lot of text and pressing Ctrl+C doesn't properly place the cursor and scroll the buffer, unless the cursor is at the end. That might also be worth investigating in the future (minor issue). * When the viewport is full, backspacing more than 1 line of text (using Ctrl+Backspace) doesn't erase all of the affected lines, because `COOKED_READ_DATA::_erase` uses the same `WriteCharsLegacy` function to write whitespace to erase that text. It's only gone after typing one more character. I've written the code to mostly fix this, but decided against it as I considered the problem to be too niche to warrant extra code. Closes #15899 ## Validation Steps Performed * Generate some text to paste in PowerShell: ```pwsh "" + (0..512 | % { "word" + $_.ToString().PadLeft(4, "0") }) ``` * Launch cmd.exe and paste that text * No flickering ✅ * No writing into the scrollback ✅ * No weird behavior when backspacing ✅
claunia added the pull-request label 2026-01-31 09:42:54 +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#30782
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?