std/terminal

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This module contains a few procedures to control the terminal (also called console). On UNIX, the implementation simply uses ANSI escape sequences and does not depend on any other module, on Windows it uses the Windows API. Changing the style is permanent even after program termination! Use the code exitprocs.addExitProc(resetAttributes) to restore the defaults. Similarly, if you hide the cursor, make sure to unhide it with showCursor before quitting.

Progress bar

Basic progress bar example:

Example: cmd: -r:off

import std/terminal
import std/[os, strutils]

for i in 0..100:
  stdout.styledWriteLine(fgRed, "0% ", fgWhite, '#'.repeat i, if i > 50: fgGreen else: fgYellow, "\t", $i , "%")
  sleep 42
  cursorUp 1
  eraseLine()

stdout.resetAttributes()

Playing with colorful and styled text

Procs like styledWriteLine, styledEcho etc. have a temporary effect on text parameters. Style parameters only affect the text parameter right after them. After being called, these procs will reset the default style of the terminal. While setBackGroundColor, setForeGroundColor etc. have a lasting influence on the terminal, you can use resetAttributes to reset the default style of the terminal.

Example: cmd: -r:off

import std/terminal
stdout.styledWriteLine({styleBright, styleBlink, styleUnderscore}, "styled text ")
stdout.styledWriteLine(fgRed, "red text ")
stdout.styledWriteLine(fgWhite, bgRed, "white text in red background")
stdout.styledWriteLine(" ordinary text without style ")

stdout.setBackGroundColor(bgCyan, true)
stdout.setForeGroundColor(fgBlue)
stdout.write("blue text in cyan background")
stdout.resetAttributes()

# You can specify multiple text parameters. Style parameters
# only affect the text parameter right after them.
styledEcho styleBright, fgGreen, "[PASS]", resetStyle, fgGreen, " Yay!"

stdout.styledWriteLine(fgRed, "red text ", styleBright, "bold red", fgDefault, " bold text")

Types

BackgroundColor = enum
  bgBlack = 40,             ## black
  bgRed,                    ## red
  bgGreen,                  ## green
  bgYellow,                 ## yellow
  bgBlue,                   ## blue
  bgMagenta,                ## magenta
  bgCyan,                   ## cyan
  bgWhite,                  ## white
  bg8Bit,                   ## 256-color (not supported, see `enableTrueColors` instead.)
  bgDefault                  ## default terminal background color
Terminal's background colors.   Source   Edit
ForegroundColor = enum
  fgBlack = 30,             ## black
  fgRed,                    ## red
  fgGreen,                  ## green
  fgYellow,                 ## yellow
  fgBlue,                   ## blue
  fgMagenta,                ## magenta
  fgCyan,                   ## cyan
  fgWhite,                  ## white
  fg8Bit,                   ## 256-color (not supported, see `enableTrueColors` instead.)
  fgDefault                  ## default terminal foreground color
Terminal's foreground colors.   Source   Edit
Style = enum
  styleBright = 1,          ## bright text
  styleDim,                 ## dim text
  styleItalic,              ## italic (or reverse on terminals not supporting)
  styleUnderscore,          ## underscored text
  styleBlink,               ## blinking/bold text
  styleBlinkRapid,          ## rapid blinking/bold text (not widely supported)
  styleReverse,             ## reverse
  styleHidden,              ## hidden text
  styleStrikethrough         ## strikethrough
Different styles for text output.   Source   Edit
TerminalCmd = enum
  resetStyle,               ## reset attributes
  fgColor,                  ## set foreground's true color
  bgColor                    ## set background's true color
commands that can be expressed as arguments   Source   Edit

Consts

ansiResetCode = "\e[0m"
  Source   Edit

Procs

proc ansiBackgroundColorCode(color: Color): string {....raises: [ValueError],
    tags: [].}
  Source   Edit
proc ansiForegroundColorCode(color: Color): string {....raises: [ValueError],
    tags: [].}
  Source   Edit
proc ansiForegroundColorCode(fg: ForegroundColor; bright = false): string {.
    ...raises: [ValueError], tags: [].}
  Source   Edit
proc ansiStyleCode(style: int): string {....raises: [ValueError], tags: [].}
  Source   Edit
proc cursorBackward(f: File; count = 1) {....raises: [IOError, ValueError],
    tags: [WriteIOEffect].}
Moves the cursor backward by count columns.

Example: cmd: -r:off

stdout.cursorBackward(2)
write(stdout, "Hello World!") # anything written at that location will be erased/replaced with this
  Source   Edit
proc cursorDown(f: File; count = 1) {....raises: [IOError, ValueError],
                                      tags: [WriteIOEffect].}
Moves the cursor down by count rows.

Example: cmd: -r:off

stdout.cursorDown(2)
write(stdout, "Hello World!") # anything written at that location will be erased/replaced with this
  Source   Edit
proc cursorForward(f: File; count = 1) {....raises: [IOError, ValueError],
    tags: [WriteIOEffect].}
Moves the cursor forward by count columns.

Example: cmd: -r:off

stdout.cursorForward(2)
write(stdout, "Hello World!") # anything written at that location will be erased/replaced with this
  Source   Edit
proc cursorUp(f: File; count = 1) {....raises: [IOError], tags: [WriteIOEffect].}
Moves the cursor up by count rows.

Example: cmd: -r:off

stdout.cursorUp(2)
write(stdout, "Hello World!") # anything written at that location will be erased/replaced with this
  Source   Edit
proc disableTrueColors() {....raises: [], tags: [RootEffect].}
Disables true color.   Source   Edit
proc enableTrueColors() {....raises: [], tags: [RootEffect, ReadEnvEffect].}
Enables true color.   Source   Edit
proc eraseLine(f: File) {....raises: [IOError, ValueError], tags: [WriteIOEffect].}
Erases the entire current line.

Example: cmd: -r:off

write(stdout, "never mind")
stdout.eraseLine() # nothing will be printed on the screen
  Source   Edit
proc eraseScreen(f: File) {....raises: [IOError], tags: [WriteIOEffect].}
Erases the screen with the background colour and moves the cursor to home.   Source   Edit
proc getch(): char {....raises: [IOError, EOFError], tags: [ReadIOEffect].}
Reads a single character from the terminal, blocking until it is entered. The character is not printed to the terminal.   Source   Edit
proc hideCursor(f: File) {....raises: [IOError], tags: [WriteIOEffect].}
Hides the cursor.   Source   Edit
proc isatty(f: File): bool {....raises: [], tags: [].}
Returns true if f is associated with a terminal device.   Source   Edit
proc isTrueColorSupported(): bool {....raises: [], tags: [RootEffect].}
Returns true if a terminal supports true color.   Source   Edit
proc readPasswordFromStdin(prompt = "password: "): string {....raises: [IOError],
    tags: [ReadIOEffect, WriteIOEffect].}
Reads a password from stdin without printing it.   Source   Edit
proc readPasswordFromStdin(prompt: string; password: var string): bool {.
    ...tags: [ReadIOEffect, WriteIOEffect], raises: [IOError].}
  Source   Edit
proc resetAttributes() {.noconv, ...raises: [IOError], tags: [WriteIOEffect].}
Resets all attributes on stdout. It is advisable to register this as a quit proc with exitprocs.addExitProc(resetAttributes).   Source   Edit
proc resetAttributes(f: File) {....raises: [IOError], tags: [WriteIOEffect].}
Resets all attributes.   Source   Edit
proc setBackgroundColor(f: File; bg: BackgroundColor; bright = false) {.
    ...raises: [IOError, ValueError], tags: [WriteIOEffect].}
Sets the terminal's background color.   Source   Edit
proc setBackgroundColor(f: File; color: Color) {....raises: [IOError, ValueError],
    tags: [RootEffect, WriteIOEffect].}
Sets the terminal's background true color.   Source   Edit
proc setCursorPos(f: File; x, y: int) {....raises: [IOError, ValueError],
                                        tags: [WriteIOEffect].}
Sets the terminal's cursor to the (x,y) position. (0,0) is the upper left of the screen.   Source   Edit
proc setCursorXPos(f: File; x: int) {....raises: [IOError, ValueError],
                                      tags: [WriteIOEffect].}
Sets the terminal's cursor to the x position. The y position is not changed.   Source   Edit
proc setForegroundColor(f: File; color: Color) {....raises: [IOError, ValueError],
    tags: [RootEffect, WriteIOEffect].}
Sets the terminal's foreground true color.   Source   Edit
proc setForegroundColor(f: File; fg: ForegroundColor; bright = false) {.
    ...raises: [IOError, ValueError], tags: [WriteIOEffect].}
Sets the terminal's foreground color.   Source   Edit
proc setStyle(f: File; style: set[Style]) {....raises: [IOError, ValueError],
    tags: [WriteIOEffect].}
Sets the terminal style.   Source   Edit
proc showCursor(f: File) {....raises: [IOError], tags: [WriteIOEffect].}
Shows the cursor.   Source   Edit
proc terminalHeight(): int {....raises: [ValueError], tags: [ReadEnvEffect].}
Returns some reasonable terminal height from either standard file descriptors, controlling terminal, environment variables or tradition. Zero is returned if the height could not be determined.   Source   Edit
proc terminalHeightIoctl(fds: openArray[int]): int {....raises: [], tags: [].}
Returns terminal height from first fd that supports the ioctl.   Source   Edit
proc terminalSize(): tuple[w, h: int] {....raises: [ValueError],
                                        tags: [ReadEnvEffect].}
Returns the terminal width and height as a tuple. Internally calls terminalWidth and terminalHeight, so the same assumptions apply.   Source   Edit
proc terminalWidth(): int {....raises: [ValueError], tags: [ReadEnvEffect].}
Returns some reasonable terminal width from either standard file descriptors, controlling terminal, environment variables or tradition.   Source   Edit
proc terminalWidthIoctl(fds: openArray[int]): int {....raises: [], tags: [].}
Returns terminal width from first fd that supports the ioctl.   Source   Edit
proc writeStyled(txt: string; style: set[Style] = {styleBright}) {.
    ...raises: [IOError, ValueError], tags: [WriteIOEffect].}
Writes the text txt in a given style to stdout.   Source   Edit

Macros

macro styledWrite(f: File; m: varargs[typed]): untyped
Similar to write, but treating terminal style arguments specially. When some argument is Style, set[Style], ForegroundColor, BackgroundColor or TerminalCmd then it is not sent directly to f, but instead corresponding terminal style proc is called.

Example: cmd: -r:off

stdout.styledWrite(fgRed, "red text ")
stdout.styledWrite(fgGreen, "green text")
  Source   Edit

Templates

template ansiBackgroundColorCode(color: static[Color]): string
  Source   Edit
template ansiForegroundColorCode(color: static[Color]): string
  Source   Edit
template ansiForegroundColorCode(fg: static[ForegroundColor];
                                 bright: static[bool] = false): string
  Source   Edit
template ansiStyleCode(style: static[Style]): string
  Source   Edit
template ansiStyleCode(style: Style): string
  Source   Edit
template cursorBackward(count = 1)
  Source   Edit
template cursorDown(count = 1)
  Source   Edit
template cursorForward(count = 1)
  Source   Edit
template cursorUp(count = 1)
  Source   Edit
template eraseLine()
  Source   Edit
template eraseScreen()
  Source   Edit
template hideCursor()
  Source   Edit
template setBackgroundColor(bg: BackgroundColor; bright = false)
  Source   Edit
template setBackgroundColor(color: Color)
  Source   Edit
template setCursorPos(x, y: int)
  Source   Edit
template setCursorXPos(x: int)
  Source   Edit
template setForegroundColor(color: Color)
  Source   Edit
template setForegroundColor(fg: ForegroundColor; bright = false)
  Source   Edit
template setStyle(style: set[Style])
  Source   Edit
template showCursor()
  Source   Edit
template styledEcho(args: varargs[untyped])
Echoes styles arguments to stdout using styledWriteLine.   Source   Edit
template styledWriteLine(f: File; args: varargs[untyped])
Calls styledWrite and appends a newline at the end.

Example:

proc error(msg: string) =
  styledWriteLine(stderr, fgRed, "Error: ", resetStyle, msg)
  Source   Edit