Console Virtual Terminal Sequences

• 07/12/2018
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Virtual terminal sequences are control character sequences that can control cursor movement, color/font mode, and other operations when written to the output stream. Sequences may also be received on the input stream in response to an output stream query information sequence or as an encoding of user input when the appropriate mode is set.

You can use GetConsoleMode and SetConsoleMode functions to configure this behavior. A sample of the suggested way to enable virtual terminal behaviors is included at the end of this document.

The behavior of the following sequences is based on the VT100 and derived terminal emulator technologies, most specifically the xterm terminal emulator. More information about terminal sequences can be found at http://vt100.net and at http://invisible-island.net/xterm/ctlseqs/ctlseqs.html.

Output Sequences

The following terminal sequences are intercepted by the console host when written into the output stream, if the ENABLE_VIRTUAL_TERMINAL_PROCESSING flag is set on the screen buffer handle using the SetConsoleMode function. Note that the DISABLE_NEWLINE_AUTO_RETURN flag may also be useful in emulating the cursor positioning and scrolling behavior of other terminal emulators in relation to characters written to the final column in any row.

Simple Cursor Positioning

In all of the following descriptions, ESC is always the hexadecimal value 0x1B. No spaces are to be included in terminal sequences. For an example of how these sequences are used in practice, please see the example at the end of this topic.

The following table describes simple escape sequences with a single action command directly after the ESC character. These sequences have no parameters and take effect immediately.

All commands in this table are generally equivalent to calling the SetConsoleCursorPosition console API to place the cursor.

Cursor movement will be bounded by the current viewport into the buffer. Scrolling (if available) will not occur.

Note
* If there are scroll margins set, RI inside the margins will scroll only the contents of the margins, and leave the viewport unchanged. (See Scrolling Margins)

**There will be no value saved in memory until the first use of the save command. The only way to access the saved value is with the restore command.

Cursor Positioning

The following tables encompass Control Sequence Introducer (CSI) type sequences. All CSI sequences start with ESC (0x1B) followed by [ (left bracket, 0x5B) and may contain parameters of variable length to specify more information for each operation. This will be represented by the shorthand <n>. Each table below is grouped by functionality with notes below each table explaining how the group works.

For all parameters, the following rules apply unless otherwise noted:

• <n> represents the distance to move and is an optional parameter
• If <n> is omitted or equals 0, it will be treated as a 1
• <n> cannot be larger than 32,767 (maximum short value)
• <n> cannot be negative

All commands in this section are generally equivalent to calling the SetConsoleCursorPosition console API.

Cursor movement will be bounded by the current viewport into the buffer. Scrolling (if available) will not occur.

Note
*<x> and <y> parameters have the same limitations as <n> above. If <x> and <y> are omitted, they will be set to 1;1.

**ANSI.sys historical documentation can be found at https://msdn.microsoft.com/library/cc722862.aspx and is implemented for convenience/compatibility.

Cursor Visibility

The following commands control the visibility of the cursor and its blinking state. The DECTCEM sequences are generally equivalent to calling SetConsoleCursorInfo console API to toggle cursor visibility.

Viewport Positioning

All commands in this section are generally equivalent to calling ScrollConsoleScreenBuffer console API to move the contents of the console buffer.

Caution The command names are misleading. Scroll refers to which direction the text moves during the operation, not which way the viewport would seem to move.

The text is moved starting with the line the cursor is on. If the cursor is on the middle row of the viewport, then scroll up would move the bottom half of the viewport, and insert blank lines at the bottom. Scroll down would move the top half of the viewport’s rows, and insert new lines at the top.

Also important to note is scroll up and down are also affected by the scrolling margins. Scroll up and down won’t affect any lines outside the scrolling margins.

The default value for <n> is 1, and the value can be optionally omitted.

Text Modification

All commands in this section are generally equivalent to calling FillConsoleOutputCharacter, FillConsoleOutputAttribute, and ScrollConsoleScreenBuffer console APIs to modify the text buffer contents.

Note
For IL and DL, only the lines in the scrolling margins (see Scrolling Margins) are affected. If no margins are set, the default margin borders are the current viewport. If lines would be shifted below the margins, they are discarded. When lines are deleted, blank lines are inserted at the bottom of the margins, lines from outside the viewport are never affected.

For each of the sequences, the default value for <n> if it is omitted is 0.

For the following commands, the parameter <n> has 3 valid values:

• 0 erases from the current cursor position (inclusive) to the end of the line/display
• 1 erases from the beginning of the line/display up to and including the current cursor position
• 2 erases the entire line/display

Text Formatting

All commands in this section are generally equivalent to calling SetConsoleTextAttribute console APIs to adjust the formatting of all future writes to the console output text buffer.

This command is special in that the <n> position below can accept between 0 and 16 parameters separated by semicolons.

When no parameters are specified, it is treated the same as a single 0 parameter.

The following table of values can be used in <n> to represent different formatting modes.

Formatting modes are applied from left to right. Applying competing formatting options will result in the right-most option taking precedence.

For options that specify colors, the colors will be used as defined in the console color table which can be modified using the SetConsoleScreenBufferInfoEx API. If the table is modified to make the “blue” position in the table display an RGB shade of red, then all calls to Foreground Blue will display that red color until otherwise changed.

Extended Colors

Some virtual terminal emulators support a palette of colors greater than the 16 colors provided by the Windows Console. For these extended colors, the Windows Console will choose the nearest appropriate color from the existing 16 color table for display. Unlike typical SGR values above, the extended values will consume additional parameters after the initial indicator according to the table below.

*The 88 and 256 color palettes maintained internally for comparison are based from the xterm terminal emulator. The comparison/rounding tables cannot be modified at this time.

Screen Colors

The following command allows the application to set the screen colors palette values to any RGB value.

The RGB values should be hexadecimal values between 0 and ff, and separated by the forward-slash character (e.g. rgb:1/24/86).

Note that this sequence is an OSC “Operating system command” sequence, and not a CSI like many of the other sequences listed, and as such start with “\x1b]”, not “\x1b[”.

Mode Changes

These are sequences that control the input modes. There are two different sets of input modes, the Cursor Keys Mode and the Keypad Keys Mode. The Cursor Keys Mode controls the sequences that are emitted by the arrow keys as well as Home and End, while the Keypad Keys Mode controls the sequences emitted by the keys on the numpad primarily, as well as the function keys.

Each of these modes are simple boolean settings – the Cursor Keys Mode is either Normal (default) or Application, and the Keypad Keys Mode is either Numeric (default) or Application.

See the Cursor Keys and Numpad & Function Keys sections for the sequences emitted in these modes.

Query State

All commands in this section are generally equivalent to calling Get* console APIs to retrieve status information about the current console buffer state.

Note These queries will emit their responses into the console input stream immediately after being recognized on the output stream while ENABLE_VIRTUAL_TERMINAL_PROCESSING is set. The ENABLE_VIRTUAL_TERMINAL_INPUT flag does not apply to query commands as it is assumed that an application making the query will always want to receive the reply.

Tabs

While the windows console traditionally expects tabs to be exclusively eight characters wide, *nix applications utilizing certain sequences can manipulate where the tab stops are within the console windows to optimize cursor movement by the application.

The following sequences allow an application to set the tab stop locations within the console window, remove them, and navigate between them.

• For both CHT and CBT, <n> is an optional parameter that (default=1) indicating how many times to advance the cursor in the specified direction.
• If there are no tab stops set via HTS, CHT and CBT will treat the first and last columns of the window as the only two tab stops.
• Using HTS to set a tab stop will also cause the console to navigate to the next tab stop on the output of a TAB (0x09, ‘\t’) character, in the same manner as CHT.

Designate Character Set

The following sequences allow a program to change the active character set mapping. This allows a program to emit 7-bit ASCII characters, but have them displayed as other glyphs on the terminal screen itself. Currently, the only two supported character sets are ASCII (default) and the DEC Special Graphics Character Set. See http://vt100.net/docs/vt220-rm/table2-4.html for a listing of all of the characters represented by the DEC Special Graphics Character Set.

Notably, the DEC Line Drawing mode is used for drawing borders in console applications. The following table shows what ASCII character maps to which line drawing character.

Scrolling Margins

The following sequences allow a program to configure the “scrolling region” of the screen that is affected by scrolling operations. This is a subset of the rows that are adjusted when the screen would otherwise scroll, for example, on a ‘\n’ or RI. These margins also affect the rows modified by Insert Line (IL) and Delete Line (DL), Scroll Up (SU) and Scroll Down (SD).

The scrolling margins can be especially useful for having a portion of the screen that doesn’t scroll when the rest of the screen is filled, such as having a title bar at the top or a status bar at the bottom of your application.

For DECSTBM, there are two optional parameters, <t> and <b>, which are used to specify the rows that represent the top and bottom lines of the scroll region, inclusive. If the parameters are omitted, <t> defaults to 1 and <b> defaults to the current viewport height.

Scrolling margins are per-buffer, so importantly, the Alternate Buffer and Main Buffer maintain separate scrolling margins settings (so a full screen application in the alternate buffer will not poison the main buffer’s margins).

Window Title

The following commands allows the application to set the title of the console window to the given <string> parameter. The string must be less than 255 characters to be accepted. This is equivalent to calling SetConsoleTitle with the given string.

Note that these sequences are OSC “Operating system command” sequences, and not a CSI like many of the other sequences listed, and as such starts with “\x1b]”, not “\x1b[”.

The terminating character here is the “Bell” character, ‘\x07’

Alternate Screen Buffer

*Nix style applications often utilize an alternate screen buffer, so that they can modify the entire contents of the buffer, without affecting the application that started them. The alternate buffer is exactly the dimensions of the window, without any scrollback region.

For an example of this behavior, consider when vim is launched from bash. Vim uses the entirety of the screen to edit the file, then returning to bash leaves the original buffer unchanged.

Window Width

The following sequences can be used to control the width of the console window. They are roughly equivalent to the calling the SetConsoleScreenBufferInfoEx console API to set the window width.

Soft Reset

The following sequence can be used to reset certain properties to their default values.The following properties are reset to the following default values (also listed are the sequences that control those properties):

• Cursor visibility: visible (DECTEM)
• Numeric Keypad: Numeric Mode (DECNKM)
• Cursor Keys Mode: Normal Mode (DECCKM)
• Top and Bottom Margins: Top=1, Bottom=Console height (DECSTBM)
• Character Set: US ASCII
• Graphics Rendition: Default/Off (SGR)
• Save cursor state: Home position (0,0) (DECSC)

Input Sequences

The following terminal sequences are emitted by the console host on the input stream if the ENABLE_VIRTUAL_TERMINAL_INPUT flag is set on the input buffer handle using the SetConsoleMode flag.

There are two internal modes that control which sequences are emitted for the given input keys, the Cursor Keys Mode and the Keypad Keys Mode. These are described in the Mode Changes section.

Cursor Keys

Additionally, if Ctrl is pressed with any of these keys, the following sequences are emitted instead, regardless of the Cursor Keys Mode:

Numpad & Function Keys

Modifiers

Alt is treated by prefixing the sequence with an escape: ESC <c> where <c> is the character passed by the operating system. Alt+Ctrl is handled the same way except that the operating system will have pre-shifted the <c> key to the appropriate control character which will be relayed to the application.

Ctrl is generally passed through exactly as received from the system. This is typically a single character shifted down into the control character reserved space (0x0-0x1f). For example, Ctrl+@ (0x40) becomes NUL (0x00), Ctrl+[ (0x5b) becomes ESC (0x1b), etc. A few Ctrl key combinations are treated specially according to the following table:

Note Left Ctrl + Right Alt is treated as AltGr. When both are seen together, they will be stripped and the Unicode value of the character presented by the system will be passed into the target. The system will pre-translate AltGr values according to the current system input settings.

Samples

Example of SGR terminal sequences

The following code provides several examples of text formatting.

#include <stdio.h>
#include <wchar.h>
#include <windows.h>

int main()
{
    // Set output mode to handle virtual terminal sequences
    HANDLE hOut = GetStdHandle(STD_OUTPUT_HANDLE);
    if (hOut == INVALID_HANDLE_VALUE)
    {
        return GetLastError();
    }

    DWORD dwMode = 0;
    if (!GetConsoleMode(hOut, &dwMode))
    {
        return GetLastError();
    }

    dwMode |= ENABLE_VIRTUAL_TERMINAL_PROCESSING;
    if (!SetConsoleMode(hOut, dwMode))
    {
        return GetLastError();
    }

    // Try some Set Graphics Rendition (SGR) terminal escape sequences
    wprintf(L"\x1b[31mThis text has a red foreground using SGR.31.\r\n");
    wprintf(L"\x1b[1mThis text has a bright (bold) red foreground using SGR.1 to affect the previous color setting.\r\n");
    wprintf(L"\x1b[mThis text has returned to default colors using SGR.0 implicitly.\r\n");
    wprintf(L"\x1b[34;46mThis text shows the foreground and background change at the same time.\r\n");
    wprintf(L"\x1b[0mThis text has returned to default colors using SGR.0 explicitly.\r\n");
    wprintf(L"\x1b[31;32;33;34;35;36;101;102;103;104;105;106;107mThis text attempts to apply many colors in the same command. Note the colors are applied from left to right so only the right-most option of foreground cyan (SGR.36) and background bright white (SGR.107) is effective.\r\n");
    wprintf(L"\x1b[39mThis text has restored the foreground color only.\r\n");
    wprintf(L"\x1b[49mThis text has restored the background color only.\r\n");

    return 0;
}

Note In the previous example, the string '\x1b[31m' is the implementation of ESC [ <n> m with <n> being 31.

The following graphic shows the output of the previous code example.

Example of Enabling Virtual Terminal Processing

The following code provides an example of the recommended way to enable virtual terminal processing for an application. The intent of the sample is to demonstrate:

1. The existing mode should always be retrieved via GetConsoleMode and analyzed before being set with SetConsoleMode.

2. Checking whether SetConsoleMode returns 0 and GetLastError returns STATUS_INVALID_PARAMETER is the current mechanism to determine when running on a down-level system. An application receiving STATUS_INVALID_PARAMETER with one of the newer console mode flags in the bit field should gracefully degrade behavior and try again.

#include <stdio.h>
#include <wchar.h>
#include <windows.h>

int main()
{
    // Set output mode to handle virtual terminal sequences
    HANDLE hOut = GetStdHandle(STD_OUTPUT_HANDLE);
    if (hOut == INVALID_HANDLE_VALUE)
    {
        return false;
    }
    HANDLE hIn = GetStdHandle(STD_INPUT_HANDLE);
    if (hIn == INVALID_HANDLE_VALUE)
    {
        return false;
    }

    DWORD dwOriginalOutMode = 0;
    DWORD dwOriginalInMode = 0;
    if (!GetConsoleMode(hOut, &dwOriginalOutMode))
    {
        return false;
    }
    if (!GetConsoleMode(hIn, &dwOriginalInMode))
    {
        return false;
    }

    DWORD dwRequestedOutModes = ENABLE_VIRTUAL_TERMINAL_PROCESSING | DISABLE_NEWLINE_AUTO_RETURN;
    DWORD dwRequestedInModes = ENABLE_VIRTUAL_TERMINAL_INPUT;

    DWORD dwOutMode = dwOriginalOutMode | dwRequestedOutModes;
    if (!SetConsoleMode(hOut, dwOutMode))
    {
        // we failed to set both modes, try to step down mode gracefully.
        dwRequestedOutModes = ENABLE_VIRTUAL_TERMINAL_PROCESSING;
        dwOutMode = dwOriginalOutMode | dwRequestedOutModes;
        if (!SetConsoleMode(hOut, dwOutMode))
        {
            // Failed to set any VT mode, can't do anything here.
            return -1;
        }
    }

    DWORD dwInMode = dwOriginalInMode | ENABLE_VIRTUAL_TERMINAL_INPUT;
    if (!SetConsoleMode(hIn, dwInMode))
    {
        // Failed to set VT input mode, can't do anything here.
        return -1;
    }

    return 0;
}

Example of Select Anniversary Update Features

The following example is intended to be a more robust example of code using a variety of escape sequences to manipulate the buffer, with an emphasis on the features added in the Anniversary Update for Windows 10.

This example makes use of the alternate screen buffer, manipulating tab stops, setting scrolling margins, and changing the character set.

//
//    Copyright (C) Microsoft.  All rights reserved.
//
#define DEFINE_CONSOLEV2_PROPERTIES

// System headers
#include <windows.h>

// Standard library C-style
#include <wchar.h>
#include <stdlib.h>
#include <stdio.h>

#define ESC "\x1b"
#define CSI "\x1b["

bool EnableVTMode()
{
    // Set output mode to handle virtual terminal sequences
    HANDLE hOut = GetStdHandle(STD_OUTPUT_HANDLE);
    if (hOut == INVALID_HANDLE_VALUE)
    {
        return false;
    }

    DWORD dwMode = 0;
    if (!GetConsoleMode(hOut, &dwMode))
    {
        return false;
    }

    dwMode |= ENABLE_VIRTUAL_TERMINAL_PROCESSING;
    if (!SetConsoleMode(hOut, dwMode))
    {
        return false;
    }
    return true;
}

void PrintVerticalBorder()
{
    printf(ESC "(0");       // Enter Line drawing mode
    printf(CSI "104;93m");   // bright yellow on bright blue
    printf("x");            // in line drawing mode, \x78 -> \u2502 "Vertical Bar"
    printf(CSI "0m");       // restore color
    printf(ESC "(B");       // exit line drawing mode
}

void PrintHorizontalBorder(COORD const Size, bool fIsTop)
{
    printf(ESC "(0");       // Enter Line drawing mode
    printf(CSI "104;93m");  // Make the border bright yellow on bright blue
    printf(fIsTop? "l" : "m"); // print left corner 

    for (int i = 1; i < Size.X - 1; i++) 
        printf("q"); // in line drawing mode, \x71 -> \u2500 "HORIZONTAL SCAN LINE-5"

    printf(fIsTop? "k" : "j"); // print right corner
    printf(CSI "0m");
    printf(ESC "(B");       // exit line drawing mode
}

void PrintStatusLine(char* const pszMessage, COORD const Size)
{
    printf(CSI "%d;1H", Size.Y);
    printf(CSI "K"); // clear the line
    printf(pszMessage);  
}

int __cdecl wmain(int argc, WCHAR* argv[])
{   
    argc; // unused
    argv; // unused
    //First, enable VT mode
    bool fSuccess = EnableVTMode();
    if (!fSuccess)
    {
        printf("Unable to enter VT processing mode. Quitting.\n");
        return -1;
    }
    HANDLE hOut = GetStdHandle(STD_OUTPUT_HANDLE);
    if (hOut == INVALID_HANDLE_VALUE)
    {
        printf("Couldn't get the console handle. Quitting.\n");
        return -1;
    }

    CONSOLE_SCREEN_BUFFER_INFO ScreenBufferInfo;
    GetConsoleScreenBufferInfo(hOut, &ScreenBufferInfo);
    COORD Size;
    Size.X = ScreenBufferInfo.srWindow.Right - ScreenBufferInfo.srWindow.Left + 1;
    Size.Y = ScreenBufferInfo.srWindow.Bottom -  ScreenBufferInfo.srWindow.Top + 1;

    // Enter the alternate buffer
    printf(CSI "?1049h");

    // Clear screen, tab stops, set, stop at columns 16, 32
    printf(CSI "1;1H");
    printf(CSI "2J"); // Clear screen

    int iNumTabStops = 4; // (0, 20, 40, width)
    printf(CSI "3g"); // clear all tab stops
    printf(CSI "1;20H"); // Move to column 20
    printf(ESC "H"); // set a tab stop

    printf(CSI "1;40H"); // Move to column 40
    printf(ESC "H"); // set a tab stop

    // Set scrolling margins to 3, h-2
    printf(CSI "3;%dr", Size.Y-2);
    int iNumLines = Size.Y - 4;

    printf(CSI "1;1H");
    printf(CSI "102;30m");
    printf("Windows 10 Anniversary Update - VT Example"); 
    printf(CSI "0m");

    // Print a top border - Yellow
    printf(CSI "2;1H");
    PrintHorizontalBorder(Size, true);

    // // Print a bottom border
    printf(CSI "%d;1H", Size.Y-1);
    PrintHorizontalBorder(Size, false);

    wchar_t wch;

    // draw columns
    printf(CSI "3;1H"); 
    int line = 0;
    for (line = 0; line < iNumLines * iNumTabStops; line++)
    {
        PrintVerticalBorder();
        if (line + 1 != iNumLines * iNumTabStops) // don't advance to next line if this is the last line
            printf("\t"); // advance to next tab stop

    }

    PrintStatusLine("Press any key to see text printed between tab stops.", Size);
    wch = _getwch();

    // Fill columns with output
    printf(CSI "3;1H"); 
    for (line = 0; line < iNumLines; line++)
    {
        int tab = 0;
        for (tab = 0; tab < iNumTabStops-1; tab++)
        {
            PrintVerticalBorder();
            printf("line=%d", line);
            printf("\t"); // advance to next tab stop
        }
        PrintVerticalBorder();// print border at right side
        if (line+1 != iNumLines)
            printf("\t"); // advance to next tab stop, (on the next line)
    }

    PrintStatusLine("Press any key to demonstrate scroll margins", Size);
    wch = _getwch();

    printf(CSI "3;1H"); 
    for (line = 0; line < iNumLines * 2; line++)
    {
        printf(CSI "K"); // clear the line
        int tab = 0;
        for (tab = 0; tab < iNumTabStops-1; tab++)
        {
            PrintVerticalBorder();
            printf("line=%d", line);
            printf("\t"); // advance to next tab stop
        }
        PrintVerticalBorder(); // print border at right side
        if (line+1 != iNumLines * 2)
        {
            printf("\n"); //Advance to next line. If we're at the bottom of the margins, the text will scroll.
            printf("\r"); //return to first col in buffer
        }
    }

    PrintStatusLine("Press any key to exit", Size);
    wch = _getwch();

    // Exit the alternate buffer
    printf(CSI "?1049l");

}