System.Console.ANSI

ANSI colors can be set on three different layers

ANSI text underlining

ANSI blink speeds: values other than NoBlink are not widely supported

ANSI's eight standard colors. They come in two intensities, which are controlled by ColorIntensity. Many terminals allow the colors of the standard palette to be customised, so that, for example, setSGR [ SetColor Foreground Vivid Green ] may not result in bright green characters.

ANSI's standard colors come in two intensities

ANSI general console intensity: usually treated as setting the font style (e.g. BoldIntensity causes text to be bold)

ANSI Select Graphic Rendition (SGR) command

In respect of colors, there are three alternative commands:

1. the 'ANSI' standards allow for eight standard colors (with two intensities). Windows and many other terminals (including xterm) allow the user to redefine the standard colors (so, for example Vivid Green may not correspond to bright green;

2. an extension of the standard that allows true colors (24 bit color depth) in RGB space. This is usually the best alternative for more colors; and

3. another extension that allows a palette of 256 colors, each color specified by an index. Xterm provides a protocol for a palette of 256 colors that many other terminals, including Windows 10, follow. Some terminals (including xterm) allow the user to redefine some or all of the palette colors.

Given xterm's standard protocol for a 256-color palette, returns the index to that part of the palette which is a spectrum of 24 grays, from dark gray (0) to near white (23) (black and white are themselves excluded). Throws an error if the gray is outside of the range 0 to 23. An example of use is:

>>> setSGR [ SetPaletteColor $ xterm24LevelGray 12 ] -- Gray50

Given xterm's standard protocol for a 256-color palette, returns the index to that part of the palette which is a 6 level (6x6x6) color cube of 216 RGB colors. Throws an error if any of the red, green or blue channels is outside the range 0 to 5. An example of use is:

>>> setSGR [ SetPaletteColor $ xterm6LevelRGB 5 2 0 ] -- Dark Orange

Given xterm's standard protocol for a 256-color palette, returns the index to that part of the palette which corresponds to the 'ANSI' standards' 16 standard, or 'system', colors (eight colors in two intensities). An example of use is:

>>> setSGR [ SetPaletteColor $ xtermSystem Vivid Green ]

Move the cursor to the specified column. The column numbering is 0-based (that is, the left-most column is numbered 0).

Move the cursor to the specified position (row and column). The position is 0-based (that is, the top-left corner is at row 0 column 0).

Save the cursor position in memory. The only way to access the saved value is with the restoreCursor command.

Restore the cursor position from memory. There will be no value saved in memory until the first use of the saveCursor command.

Looking for a way to get the cursors position? See getCursorPosition.

Emit the cursor position into the console input stream, immediately after being recognised on the output stream, as: ESC [ <cursor row> ; <cursor column> R

Note that the information that is emitted is 1-based (the top-left corner is at row 1 column 1) but setCursorColumn and setCursorPosition are 0-based.

In isolation of getReportedCursorPosition or getCursorPosition, this function may be of limited use on Windows operating systems because of difficulties in obtaining the data emitted into the console input stream.

Use the Alternate Screen Buffer. If currently using the Normal Screen Buffer, it will save the cursor position and switch to the Alternate Screen Buffer. It will always clear the Alternate Screen Buffer. The Alternate Screen Buffer has no scroll back facility.

It is an application's responsibility to ensure that it switches back to the Normal Screen Buffer if an exception is raised while the Alternate Screen Buffer is being used. For example, by using bracket_:

bracket_ useAlternateScreenBuffer useNormalScreenBuffer action

Use the Normal Screen Buffer. If currently using the Alternate Screen Buffer, it will clear the Alternate Screen Buffer, and switch to the Normal Screen Buffer. It will always restore the saved cursor position.

Looking for a way to get layer colors? See getLayerColor.

Emit the layerColor into the console input stream, immediately after being recognised on the output stream, as: ESC ] <Ps> ; rgb: <red> ; <green> ; <blue> <ST> where <Ps> is 10 for Foreground and 11 for Background; <red>, <green> and <blue> are the color channel values in hexadecimal (4, 8, 12 and 16 bit values are possible, although 16 bit values are most common); and <ST> is the STRING TERMINATOR (ST). ST depends on the terminal software and may be the BEL character or ESC \ characters.

This function may be of limited, or no, use on Windows operating systems because (1) the function is not supported on native terminals and is emulated, but the emulation does not work on Windows Terminal and (2) of difficulties in obtaining the data emitted into the console input stream.

Underlining is not supported.

Code to emit the foreground or backgrond layer color into the console input stream, immediately after being recognised on the output stream, as:

ESC ] <Ps> ; rgb: <red> ; <green> ; <blue> <ST>

where <Ps> is 10 for Foreground and 11 for Background; <red>, <green> and <blue> are the color channel values in hexadecimal (4, 8, 12 and 16 bit values are possible, although 16 bit values are most common); and <ST> is the STRING TERMINATOR (ST). ST depends on the terminal software and may be the BEL character or ESC \ characters.

This function may be of limited, or no, use on Windows operating systems because (1) the control character sequence is not supported on native terminals (2) of difficulties in obtaining the data emitted into the console input stream. See getReportedLayerColor.

Underlining is not supported.

Set the Select Graphic Rendition mode

Introduce a hyperlink.

Introduce a hyperlink with an identifier for the link. Some terminals support an identifier, so that hyperlinks with the same identifier are treated as connected.

Introduce a hyperlink with (key, value) parameters. Some terminals support an id parameter key, so that hyperlinks with the same id value are treated as connected.

Set the terminal window title and icon name (that is, the text for the window in the Start bar, or similar).

Code to set the terminal window title and the icon name (that is, the text for the window in the Start bar, or similar).

Use heuristics to determine whether the functions defined in this package will work with a given handle.

If the handle is not writable (that is, it cannot manage output - see System.IO.hIsWritable), then pure False is returned.

For Unix-like operating systems, the current implementation checks that: (1) the handle is a terminal; and (2) a TERM environment variable is not set to dumb (which is what the GNU Emacs text editor sets for its integrated terminal).

For Windows, the current implementation checks: first that (1) the handle is a terminal, (2) a TERM environment variable is not set to dumb, and (3) the processing of 'ANSI' control characters in output is enabled; and second, as an alternative, whether the handle is connected to a 'mintty' terminal. (That is because the function System.IO.hIsTerminalDevice is used to check if the handle is a terminal. However, where a non-native Windows terminal (such as 'mintty') is implemented using redirection, that function will not identify a handle to the terminal as a terminal.) If it is not already enabled, this function does *not* enable the processing of 'ANSI' control characters in output (see hNowSupportsANSI).

With one exception, equivalent to hSupportsANSI. The exception is that, on Windows only, if a TERM environment variable is not set to dumb and the processing of 'ANSI' control characters in output is not enabled, this function first tries to enable such processing.

@Since 1.0.1

Some terminals (e.g. Emacs) are not fully ANSI compliant but can support ANSI colors. This can be used in such cases, if colors are all that is needed.

Attempts to get the reported cursor position, combining the functions reportCursorPosition, getReportedCursorPosition and cursorPosition. Any position (row, column) is translated to be 0-based (that is, the top-left corner is at (0, 0)), consistent with setCursorColumn and setCursorPosition. (Note that the information emitted into the console input stream by reportCursorPosition is 1-based.) Returns Nothing if any data emitted by reportCursorPosition, obtained by getReportedCursorPosition, cannot be parsed by cursorPosition. Uses stdout. If stdout will be redirected, see hGetCursorPosition for a more general function.

On Windows operating systems, the function is not supported on consoles, such as mintty, that are not based on the Windows' Console API. (Command Prompt and PowerShell are based on the Console API.)

Attempts to get the reported cursor position, combining the functions hReportCursorPosition (with the specified handle), getReportedCursorPosition and cursorPosition. Any position (row, column) is translated to be 0-based (that is, the top-left corner is at (0, 0)), consistent with hSetCursorColumn and hSetCursorPosition. (Note that the information emitted into the console input stream by hReportCursorPosition is 1-based.) Returns Nothing if any data emitted by hReportCursorPosition, obtained by getReportedCursorPosition, cannot be parsed by cursorPosition.

On Windows operating systems, the function is not supported on consoles, such as mintty, that are not based on the Windows' Console API. (Command Prompt and PowerShell are based on the Console API.)

Attempts to get the reported cursor position data from the console input stream. The function is intended to be called immediately after reportCursorPosition (or related functions) have caused characters to be emitted into the stream.

For example, on a Unix-like operating system:

-- set no buffering (if 'no buffering' is not already set, the contents of
-- the buffer will be discarded, so this needs to be done before the cursor
-- positon is emitted)
hSetBuffering stdin NoBuffering
-- ensure that echoing is off
input <- bracket (hGetEcho stdin) (hSetEcho stdin) $ \_ -> do
  hSetEcho stdin False
  reportCursorPosition
  hFlush stdout -- ensure the report cursor position code is sent to the
                -- operating system
  getReportedCursorPosition

On Windows operating systems, the function is not supported on consoles, such as mintty, that are not based on the Windows' Console API. (Command Prompt and PowerShell are based on the Console API.)

Parses the characters emitted by reportCursorPosition into the console input stream. Returns the cursor row and column as a tuple.

For example, if the characters emitted by reportCursorPosition are in String input then the parser could be applied like this:

let result = readP_to_S cursorPosition input
case result of
    [] -> putStrLn $ "Error: could not parse " ++ show input
    [((row, column), _)] -> putStrLn $ "The cursor was at row " ++ show row
        ++ " and column" ++ show column ++ "."
    (_:_) -> putStrLn $ "Error: parse not unique"

Attempts to get the current terminal size (height in rows, width in columns).

There is no 'ANSI' control character sequence that reports the terminal size. So, it attempts to set the cursor position beyond the bottom right corner of the terminal and then use getCursorPosition to query the console input stream. It works only on terminals that support each step and if data can be emitted to stdin. (Use System.IO.hIsTerminalDevice to test if stdin is connected to a terminal.) Uses stdout. If stdout will be redirected, see System.IO.hGetTerminalSize for a more general function.

On Windows operating systems, the function is not supported on consoles, such as mintty, that are not based on Windows' Console API. (Command Prompt and PowerShell are based on the Console API.)

For a different approach, one that does not use control character sequences and works when stdin is redirected, see the terminal-size package.

Attempts to get the current terminal size (height in rows, width in columns), by writing control character sequences to the specified handle (which will typically be stdout or System.IO.stderr).

There is no 'ANSI' control character sequence that reports the terminal size. So, it attempts to set the cursor position beyond the bottom right corner of the terminal and then use hGetCursorPosition to query the console input stream. It works only on terminals that support each step and if data can be emitted to stdin. (Use System.IO.hIsTerminalDevice to test if stdin is connected to a terminal.)

On Windows operating systems, the function is not supported on consoles, such as mintty, that are not based on the Windows' Console API. (Command Prompt and PowerShell are based on the Console API.)

For a different approach, one that does not use control character sequences and works when stdin is redirected, see the terminal-size package.

Attempts to get the reported layer color, combining the functions reportLayerColor, getReportedLayerColor and layerColor. Any RGB color is scaled to be 16 bits per channel, the most common format reported by terminal software. Returns Nothing if any data emitted by reportLayerColor, obtained by getReportedLayerColor, cannot be parsed by layerColor. Uses stdout. If stdout will be redirected, see hGetLayerColor for a more general function.

On Windows operating systems, the function is not supported on consoles, such as mintty, that are not based on the Windows' Console API. (Command Prompt and PowerShell are based on the Console API.) This function also relies on emulation that does not work on Windows Terminal.

Underlining is not supported.

Attempts to get the reported layer color, combining the functions hReportLayerColor, getReportedLayerColor and layerColor. Any RGB color is scaled to be 16 bits per channel, the most common format reported by terminal software. Returns Nothing if any data emitted by hReportLayerColor, obtained by getReportedLayerColor, cannot be parsed by layerColor.

On Windows operating systems, the function is not supported on consoles, such as mintty, that are not based on the Windows' Console API. (Command Prompt and PowerShell are based on the Console API.) This function also relies on emulation that does not work on Windows Terminal.

Underlining is not supported.

Attempts to get the reported layer color data from the console input stream. The function is intended to be called immediately after reportLayerColor (or related functions) have caused characters to be emitted into the stream.

For example, on a Unix-like operating system:

-- set no buffering (if 'no buffering' is not already set, the contents of
-- the buffer will be discarded, so this needs to be done before the cursor
-- positon is emitted)
hSetBuffering stdin NoBuffering
-- ensure that echoing is off
input <- bracket (hGetEcho stdin) (hSetEcho stdin) $ \_ -> do
  hSetEcho stdin False
  reportLayerColor Foreground
  hFlush stdout -- ensure the report cursor position code is sent to the
                -- operating system
  getReportedLayerColor Foreground

On Windows operating systems, the function is not supported on consoles, such as mintty, that are not based on the Windows' Console API. (Command Prompt and PowerShell are based on the Console API.)

Underlining is not supported.

Parses the characters emitted by reportLayerColor into the console input stream.

For example, if the characters emitted by reportLayerColor are in String input then the parser could be applied like this:

let result = readP_to_S (layerColor layer) input
case result of
    [] -> putStrLn $ "Error: could not parse " ++ show input
    [(col, _)] -> putStrLn $ "The color was " ++ show col ++ "."
    (_:_) -> putStrLn $ "Error: parse not unique"

Underlining is not supported.

Use heuristics to determine whether a given handle will support 'ANSI' control characters in output. The function is consistent with hNowSupportsANSI.

This function is deprecated as, from version 1.0, the package no longer supports legacy versions of Windows that required emulation.