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

C0 characters in screen buffer are incorrectly interpreted as controls by conpty #6149

New Issue
Open
opened 2026-01-31 00:31:05 +00:00 by claunia · 0 comments
claunia commented 2026-01-31 00:31:05 +00:00
Owner
Copy Link

Originally created by @j4james on GitHub (Jan 26, 2020).

Environment

Windows build number: Version 10.0.18362.535
Windows Terminal version (if applicable): 0.8.10091.0

Steps to reproduce

Compile the follow C++ program, and then run the resulting executable from a cmd shell in the Windows Terminal.

#include <windows.h>
#include <string>

void main() {
    HANDLE handle = GetStdHandle(STD_OUTPUT_HANDLE);

    // Enable VT mode.
    DWORD mode;
    GetConsoleMode(handle, &mode);
    mode |= ENABLE_VIRTUAL_TERMINAL_PROCESSING;
    SetConsoleMode(handle, mode);

    // Write directly to the screen buffer with control chars.
    DWORD written = 0;
    const std::wstring text = L"\x1B[31mIs this text red?\nIs this on a new line?\n";
    WriteConsoleOutputCharacterW(handle, text.c_str(), text.length(), COORD{ 0, 0 }, &written);
}

Expected behavior

The WriteConsoleOutputCharacterW api writes directly to the screen buffer, without attempting to process any control characters. I would thus expect the text message to be output entirely on the first line of the screen buffer, with the ESC and LF control characters output as glyphs, and not interpreted. This is what it looks like in a conhost cmd shell:

image

Note that the ENABLE_VIRTUAL_TERMINAL_PROCESSING mode should have no effect on this API. I've only turned it on to make sure the code is running under the same conditions in conhost as it is in WT (which enables VT mode by default).

Actual behavior

In the Windows Terminal, the ESC and LF characters are interpreted as control characters instead of being output as glyphs. As a result, you get an escape sequence changing the text color to red, and the text will be output over multiple lines.

Depending on timing, you can also end up with other parts of the screen being redrawn incorrectly, as the terminal cursor position is now out of sync with where the conhost thinks it is (notice part of the copyright message being redrawn two lines down in red).

image

Originally created by @j4james on GitHub (Jan 26, 2020). # Environment ```none Windows build number: Version 10.0.18362.535 Windows Terminal version (if applicable): 0.8.10091.0 ``` # Steps to reproduce Compile the follow C++ program, and then run the resulting executable from a cmd shell in the Windows Terminal. ```cpp #include <windows.h> #include <string> void main() { HANDLE handle = GetStdHandle(STD_OUTPUT_HANDLE); // Enable VT mode. DWORD mode; GetConsoleMode(handle, &mode); mode |= ENABLE_VIRTUAL_TERMINAL_PROCESSING; SetConsoleMode(handle, mode); // Write directly to the screen buffer with control chars. DWORD written = 0; const std::wstring text = L"\x1B[31mIs this text red?\nIs this on a new line?\n"; WriteConsoleOutputCharacterW(handle, text.c_str(), text.length(), COORD{ 0, 0 }, &written); } ``` # Expected behavior The `WriteConsoleOutputCharacterW` api writes directly to the screen buffer, without attempting to process any control characters. I would thus expect the text message to be output entirely on the first line of the screen buffer, with the `ESC` and `LF` control characters output as glyphs, and not interpreted. This is what it looks like in a conhost cmd shell: ![image](https://user-images.githubusercontent.com/4181424/73140021-13bcb000-406c-11ea-85ae-fe8f8f3cbc81.png) Note that the `ENABLE_VIRTUAL_TERMINAL_PROCESSING` mode should have no effect on this API. I've only turned it on to make sure the code is running under the same conditions in conhost as it is in WT (which enables VT mode by default). # Actual behavior In the Windows Terminal, the `ESC` and `LF` characters are interpreted as control characters instead of being output as glyphs. As a result, you get an escape sequence changing the text color to red, and the text will be output over multiple lines. Depending on timing, you can also end up with other parts of the screen being redrawn incorrectly, as the terminal cursor position is now out of sync with where the conhost thinks it is (notice part of the copyright message being redrawn two lines down in red). ![image](https://user-images.githubusercontent.com/4181424/73140041-59797880-406c-11ea-90cc-2e5270074b0d.png)
claunia added the Area-OutputIssue-BugIn-PRArea-VTNeeds-Tag-FixProduct-Conpty labels 2026-01-31 00:31:05 +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 Area-Output Area-VT In-PR Issue-Bug Needs-Tag-Fix Product-Conpty
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#6149
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?