blessed

A curses-like library for node.js.

Example

This will render a box with ascii borders containing the text 'Hello world!', perfectly centered horizontally and vertically.

var blessed = require('blessed');

// Create a screen object.
var screen = blessed.screen();

// Create a box perfectly centered horizontally and vertically.
var box = blessed.box({
  top: 'center',
  left: 'center',
  width: '50%',
  height: '50%',
  border: {
    type: 'ascii',
    fg: '#ffffff'
  },
  fg: 'white',
  bg: 'magenta',
  content: 'Hello {bold}world{/bold}!',
  tags: true,
  hoverEffects: {
    bg: 'green'
  }
});

// Append our box to the screen.
screen.append(box);

// If our box is clicked, change the content.
box.on('click', function(data) {
  box.setContent('{center}Some different {red-fg}content{/red-fg}.{/center}');
  screen.render();
});

// If box is focused, handle `enter` and give us some more content.
box.key('enter', function() {
  box.setContent('{right}Even different {black-fg}content{/black-fg}.{/right}\n');
  box.setLine(1, 'bar');
  box.insertLine(1, 'foo');
  screen.render();
});

// Quit on Escape, q, or Control-C.
screen.key(['escape', 'q', 'C-c'], function(ch, key) {
  return process.exit(0);
});

// Focus our element.
box.focus();

// Render the screen.
screen.render();

High-level Documentation

Widgets

Blessed comes with a number of high-level widgets so you can avoid all the nasty low-level terminal stuff.

Node (from EventEmitter)

The base node which everything inherits from.

Options:

• screen - the screen to be associated with.
• parent - the desired parent.
• children - an arrray of children.

Properties:

• inherits all from EventEmitter.
• options - original options object.
• parent - parent node.
• screen - parent screen.
• children - array of node's children.
• data, _, $ - an object for any miscellanous user data.
• index - render index (document order index) of the last render call.

Events:

• inherits all from EventEmitter.
• adopt - received when node is added to a parent.
• remove - received when node is removed from it's current parent.
• reparent - received when node gains a new parent.
• attach - received when node is attached to the screen directly or somewhere in its ancestry.
• detach - received when node is detached from the screen directly or somewhere in its ancestry.

Methods:

• inherits all from EventEmitter.
• prepend(node) - prepend a node to this node's children.
• append(node) - append a node to this node's children.
• remove(node) - remove child node from node.
• insert(node, i) - insert a node to this node's children at index i.
• insertBefore(node, refNode) - insert a node to this node's children before the reference node.
• insertAfter(node, refNode) - insert a node from node after the reference node.
• detach() - remove node from its parent.
• emitDescendants(type, args..., [iterator]) - emit event for element, and recursively emit same event for all descendants.
• get(name, [default]) - get user property with a potential default value.
• set(name, value) - set user property to value.

Screen (from Node)

The screen on which every other node renders.

Options:

• program - the blessed Program to be associated with.
• smartCSR - attempt to perform CSR optimization on all possible elements (not just full-width ones, elements with uniform cells to their sides). this is known to cause flickering with elements that are not full-width, however, it is more optimal for terminal rendering.

Properties:

• inherits all from Node.
• program - the blessed Program object.
• tput - the blessed Tput object (only available if you passed tput: true to the Program constructor.)
• focused - top of the focus history stack.
• width - width of the screen (same as program.cols).
• height - height of the screen (same as program.rows).
• cols - same as screen.width.
• rows - same as screen.height.
• left, rleft - left offset, always zero.
• right, rright - right offset, always zero.
• top, rtop - top offset, always zero.
• bottom, rbottom - bottom offset, always zero.
• grabKeys - whether the focused element grabs all keypresses.
• lockKeys - prevent keypresses from being received by any element.
• hover - the currently hovered element. only set if mouse events are bound.

Events:

• inherits all from Node.
• resize - received on screen resize.
• mouse - received on mouse events.
• keypress - received on key events.
• element [name] - global events received for all elements.
• key [name] - received on key event for [name].
• focus, blur - received when the terminal window focuses/blurs. requires a terminal supporting the focus protocol and focus needs to be passed to program.enableMouse().
• prerender - received before render.
• render - received on render.

Methods:

• inherits all from Node.
• alloc() - allocate a new pending screen buffer and a new output screen buffer.
• draw(start, end) - draw the screen based on the contents of the screen buffer.
• render() - render all child elements, writing all data to the screen buffer and drawing the screen.
• clearRegion(x1, x2, y1, y2) - clear any region on the screen.
• fillRegion(attr, ch, x1, x2, y1, y2) - fill any region with a character of a certain attribute.
• focus(offset) - focus element by offset of focusable elements.
• focusPrev() - focus previous element in the index.
• focusNext() - focus next element in the index.
• focusPush(element) - push element on the focus stack (equivalent to screen.focused = el).
• focusPop()/focusLast() - pop element off the focus stack.
• saveFocus() - save the focused element.
• restoreFocus() - restore the saved focused element.
• key(name, listener) - bind a keypress listener for a specific key.
• onceKey(name, listener) - bind a keypress listener for a specific key once.
• unkey(name, listener) - remove a keypress listener for a specific key.
• spawn(file, args, options) - spawn a process in the foreground, return to blessed app after exit.
• exec(file, args, options, callback) - spawn a process in the foreground, return to blessed app after exit. executes callback on error or exit.
• readEditor([options], callback) - read data from text editor.
• setEffects(el, fel, over, out, effects, temp) - set effects based on two events and attributes.
• insertLine(n, y, top, bottom) - insert a line into the screen (using csr: this bypasses the output buffer).
• deleteLine(n, y, top, bottom) - delete a line from the screen (using csr: this bypasses the output buffer).
• insertBottom(top, bottom) - insert a line at the bottom of the screen.
• insertTop(top, bottom) - insert a line at the top of the screen.
• deleteBottom(top, bottom) - delete a line at the bottom of the screen.
• deleteTop(top, bottom) - delete a line at the top of the screen.

Element (from Node)

The base element.

Options:

• fg, bg, bold, underline - attributes.
• border - border object, see below.
• content - element's text content.
• clickable - element is clickable.
• input - element is focusable and can receive key input.
• hidden - whether the element is hidden.
• label - a simple text label for the element.
• align - text alignment: left, center, or right.
• shrink - shrink/flex/grow to content width during render.
• padding - amount of padding on the inside of the element. (does not work...yet)

Properties:

• inherits all from Node.
• border - border object.
  • type - type of border (ascii or bg). bg by default.
  • ch - character to use if bg type, default is space.
  • bg, fg - border foreground and background, must be numbers (-1 for default).
  • bold, underline - border attributes.
• position - raw width, height, and offsets.
• content - text content.
• hidden - whether the element is hidden or not.
• fg, bg - foreground and background, must be numbers (-1 for default).
• bold, underline - attributes.
• width - calculated width.
• height - calculated height.
• left - calculated absolute left offset.
• right - calculated absolute right offset.
• top - calculated absolute top offset.
• bottom - calculated absolute bottom offset.
• rleft - calculated relative left offset.
• rright - calculated relative right offset.
• rtop - calculated relative top offset.
• rbottom - calculated relative bottom offset.

Events:

• inherits all from Node.
• blur, focus - received when an element is focused or unfocused.
• mouse - received on mouse events for this element.
  • mousedown, mouseup - mouse button was pressed or released.
  • wheeldown, wheelup - wheel was scrolled down or up.
  • mouseover, mouseout - element was hovered or unhovered.
  • mousemove - mouse was moved somewhere on this element.
• keypress - received on key events for this element.
• move - received when the element is moved.
• resize - received when the element is resized.
• key [name] - received on key event for [name].

Methods:

• inherits all from Node.
• render() - write content and children to the screen buffer.
• setContent(text) - set the content.
• hide() - hide element.
• show() - show element.
• toggle() - toggle hidden/shown.
• focus() - focus element.
• key(name, listener) - bind a keypress listener for a specific key.
• onceKey(name, listener) - bind a keypress listener for a specific key once.
• unkey(name, listener) - remove a keypress listener for a specific key.
• onScreenEvent(type, listener) - same asel.on('screen', ...) except this will automatically cleanup listeners after the element is detached.

Box (from Element)

A box element which draws a simple box containing content or other elements.

Options:

• inherits all from Element.

Properties:

• inherits all from Element.

Events:

• inherits all from Element.

Methods:

• inherits all from Element.
• insertLine(i, line) - insert a line into the box's content.
• deleteLine(i) - delete a line from the box's content.
• getLine(i) - get a line from the box's content.
• setLine(i, line) - set a line in the box's content.
• clearLine(i) - clear a line from the box's content.
• insertTop(line) - insert a line at the top of the box.
• insertBottom(line) - insert a line at the bottom of the box.
• deleteTop() - delete a line at the top of the box.
• deleteBottom() - delete a line at the bottom of the box.

Line (from Box)

A simple line which can be ascii or bg styled.

Options:

• inherits all from Box.
• orientation - can be vertical or horizontal.
• type, bg, fg, ch - treated the same as a border object.

Inherits all options, properties, events, and methods from Box.

Text (from Element)

An element similar to Box, but geared towards rendering simple text elements.

Options:

• inherits all from Element.
• fill - fill the entire line with chosen bg until parent bg ends, even if there is not enough text to fill the entire width. (deprecated)
• align - text alignment: left, center, or right.

Inherits all options, properties, events, and methods from Element.

Line (from Box)

A simple line which can be ascii or bg styled.

Options:

• inherits all from Box.
• orientation - can be vertical or horizontal.
• type, bg, fg, ch - treated the same as a border object.

Inherits all options, properties, events, and methods from Box.

ScrollableBox (from Box)

A box with scrollable content.

Options:

• inherits all from Box.
• baseLimit - a limit to the childBase. default is Infinity.
• alwaysScroll - a option which causes the ignoring of childOffset. this in turn causes the childBase to change every time the element is scrolled.
• scrollbar - object enabling a scrollbar. allows ch, fg, and bg properties.

Properties:

• inherits all from Box.
• childBase - the offset of the top of the scroll content.
• childOffset - the offset of the chosen item (if there is one).

Events:

• inherits all from Box.
• scroll - received when the element is scrolled.
• resetScroll - reset scroll offset to zero.

Methods:

• scroll(offset) - scroll the content by an offset.

List (from ScrollableBox)

A scrollable list which can display selectable items.

Options:

• inherits all from ScrollableBox.
• selectFg, selectedBg - foreground and background for selected item, treated like fg and bg.
• selectedBold, selectedUnderline - character attributes for selected item, treated like bold and underline.
• mouse - whether to automatically enable mouse support for this list (allows clicking items).
• keys - use predefined keys for navigating the list.
• vi - use vi keys with the keys option.
• items - an array of strings which become the list's items.

Properties:

• inherits all from ScrollableBox.

Events:

• inherits all from ScrollableBox.
• select - received when an item is selected.
• cancel - list was canceled (when esc is pressed with the keys option).
• action - either a select or a cancel event was received.

Methods:

• inherits all from ScrollableBox.
• add(text) - add an item based on a string.
• select(index) - select an index of an item.
• move(offset) - select item based on current offset.
• up(amount) - select item above selected.
• down(amount) - select item below selected.

ScrollableText (from ScrollableBox)

A scrollable text box which can display and scroll text, as well as handle pre-existing newlines and escape codes.

Options:

• inherits all from ScrollableBox.
• mouse - whether to enable automatic mouse support for this element.
• keys - use predefined keys for navigating the text.
• vi - use vi keys with the keys option.

Properties:

• inherits all from ScrollableBox.

Events:

• inherits all from ScrollableBox.

Methods:

• inherits all from ScrollableBox.

Input (from Box)

A form input.

Textbox (from Input)

A box which allows text input.

Options:

• inherits all from Input.

Properties:

• inherits all from Input.

Events:

• inherits all from Input.

Methods:

• inherits all from Input.
• readInput(callback) - grab key events and start reading text from the keyboard. takes a callback which receives the final value.
• readEditor(callback) - open text editor in $EDITOR, read the output from the resulting file. takes a callback which receives the final value.
• clearInput - clear input.

Textarea (from Input/ScrollableText)

A box which allows multiline text input.

Options:

• inherits all from Input/ScrollableText.

Properties:

• inherits all from Input/ScrollableText.

Events:

• inherits all from Input/ScrollableText.

Methods:

• inherits all from Input/ScrollableText.
• readInput(callback) - grab key events and start reading text from the keyboard. takes a callback which receives the final value.
• readEditor(callback) - open text editor in $EDITOR, read the output from the resulting file. takes a callback which receives the final value.
• clearInput - clear input.

Button (from Input)

A button which can be focused and allows key and mouse input.

Options:

• inherits all from Input.

Properties:

• inherits all from Input.

Events:

• inherits all from ScrollableBox.
• press - received when the button is clicked/pressed.

Methods:

• inherits all from ScrollableBox.
• add(text) - add an item based on a string.
• select(index) - select an index of an item.
• move(offset) - select item based on current offset.
• up(amount) - select item above selected.
• down(amount) - select item below selected.

ProgressBar (from Input)

A progress bar allowing various styles.

Options:

• inherits all from Input.
• barFg, barBg - (completed) bar foreground and background.
• ch - the character to fill the bar with (default is space).
• filled - the amount filled (0 - 100).

Properties:

• inherits all from Input.

Events:

• inherits all from Input.
• reset - bar was reset.
• complete - bar has completely filled.

Methods:

• inherits all from Input.
• progress(amount) - progress the bar by a fill amount.
• reset() - reset the bar.

FileManager (from List)

A very simple file manager for selecting files.

Options:

• inherits all from List.
• cwd - current working directory.

Properties:

• inherits all from List.
• cwd - current working directory.

Events:

• inherits all from List.
• cd - directory was selected and navigated to.
• file - file was selected.

Methods:

• inherits all from List.
• refresh([cwd], [callback]) - refresh the file list (perform a readdir on cwd and update the list items).
• pick([cwd], callback) - pick a single file and return the path in the callback.
• reset([cwd], [callback]) - reset back to original cwd.

Positioning

Offsets may be a number, a percentage (e.g. 50%), or a keyword (e.g. center).

Dimensions may be a number, or a percentage (e.g. 50%).

Positions are treated almost exactly the same as they are in CSS/CSSOM when an element has the position: absolute CSS property.

When an element is created, it can be given coordinates in its constructor:

var box = blessed.box({
  left: 'center',
  top: 'center',
  bg: 'yellow',
  width: '50%',
  height: '50%'
});

This tells blessed to create a box, perfectly centered relative to its parent, 50% as wide and 50% as tall as its parent.

To access the calculated offsets, relative to the parent:

console.log(box.rleft);
console.log(box.rtop);

To access the calculated offsets, absolute (relative to the screen):

console.log(box.left);
console.log(box.top);

Overlapping offsets and dimensions greater than parents'

This still needs to be tested a bit, but it should work.

Content

Every element can have text content via setContent. If tags: true was passed to the element's constructor, the content can contain tags. For example:

box.setContent('hello {red-fg}{green-bg}{bold}world{/bold}{/green-bg}{/red-fg}');

To make this more concise {/} cancels all character attributes.

box.setContent('hello {red-fg}{green-bg}{bold}world{/}');

Newlines and alignment are also possible in content.

box.setContent('hello\n'
  + '{right}world{/right}\n'
  + '{center}foo{/center}');

This will produce a box that looks like:

| hello                 |
|                 world |
|          foo          |

Content can also handle SGR escape codes. This means if you got output from a program, say git log for example, you can feed it directly to an element's content and the colors will be parsed appropriately.

This means that while {red-fg}foo{/red-fg} produces ^[[31mfoo^[[39m, you could just feed ^[[31mfoo^[[39m directly to the content.

Rendering

To actually render the screen buffer, you must call render.

box.setContent('Hello world.');
screen.render();

Elements are rendered with the lower elements in the children array being painted first. In terms of the painter's algorithm, the lowest indicies in the array are the furthest away, just like in the DOM.

Optimization and CSR

NOTE: This is now automatically optimized for full-width scrollable elements.

TODO: Detect to see if there are any elements under/to the sides of non-full-width elements.

You may notice a lot of terminal apps (e.g. mutt, irssi, vim, ncmpcpp) don't have sidebars, and only have "elements" that take up the entire width of the screen. The reason for this is speed (and general cleanliness). VT-like terminals have something called a CSR (change_scroll_region) code, as well as IL (insert_line), and DL (delete_code) codes. Using these three codes, it is possible to create a very efficient rendering by avoiding redrawing the entire screen when a line is inserted or removed. Since blessed is extremely dynamic, it is hard to do this optimization automatically (blessed assumes you may create any element of any width in any position). So, there is a solution:

var box = blessed.box(...);
box.setContent('line 1\nline 2');
box.insertBottom('line 3');
box.insertBottom('line 4');
box.insertTop('line 0');
box.insertLine(1, 'line 1.5');

If your element has the same width as the screen, the line insertion will be optimized by using a combination CSR/IL/DL codes. These methods may be made smarter in the future to detect whether any elements are being overlapped to the sides.

Outputting:

| line 0            |
| line 1            |
| line 1.5          |
| line 2            |
| line 3            |
| line 4            |

Testing

• For an interactive test, see test/widget.js.
• For a less interactive position testing, see test/widget-pos.js.

Lower-Level Usage

This will actually parse the xterm terminfo and compile every string capability to a javascript function:

var Tput = require('blessed').Tput
  , tput = Tput('xterm');

console.log(tput.setaf(4) + 'hello' + tput.sgr0());

To play around with it on the command line, it works just like tput:

$ tput.js setaf 2
$ tput.js sgr0
$ echo "$(tput.js setaf 2)hello world$(tput.js sgr0)"

The main functionality is exposed in the main blessed module:

var blessed = require('blessed')
  , program = blessed();

program.key('q', function(ch, key) {
  program.clear();
  program.disableMouse();
  program.showCursor();
  program.normalBuffer();
  process.exit(0);
});

program.on('mouse', function(data) {
  if (data.action === 'mousemove') {
    program.move(data.x, data.y);
    program.bg('red');
    program.write('x');
    program.bg('!red');
  }
});

program.alternateBuffer();
program.enableMouse();
program.hideCursor();
program.clear();

program.move(1, 1);
program.bg('black');
program.write('Hello world', 'blue fg');
program.setx((program.cols / 2 | 0) - 4);
program.down(5);
program.write('Hi again!');
program.bg('!black');
program.feed();

License

Copyright (c) 2013, Christopher Jeffrey. (MIT License)

See LICENSE for more info.