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Description

A rich text editor for everyday writing

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Trix

A Rich Text Editor for Everyday Writing

Compose beautifully formatted text in your web application. Trix is a WYSIWYG editor for writing messages, comments, articles, and lists—the simple documents most web apps are made of. It features a sophisticated document model, support for embedded attachments, and outputs terse and consistent HTML.

Trix is an open-source project from Basecamp, the creators of Ruby on Rails. Millions of people trust their text to Basecamp, and we built Trix to give them the best possible editing experience. See Trix in action in the all-new Basecamp 3.

Different By Design

Most WYSIWYG editors are wrappers around HTML’s

contenteditable
and
execCommand
APIs, designed by Microsoft to support live editing of web pages in Internet Explorer 5.5, and eventually reverse-engineered and copied by other browsers.

Because these APIs were never fully specified or documented, and because WYSIWYG HTML editors are enormous in scope, each browser’s implementation has its own set of bugs and quirks, and JavaScript developers are left to resolve the inconsistencies.

Trix sidesteps these inconsistencies by treating

contenteditable
as an I/O device: when input makes its way to the editor, Trix converts that input into an editing operation on its internal document model, then re-renders that document back into the editor. This gives Trix complete control over what happens after every keystroke, and avoids the need to use
execCommand
at all.

Built for the Modern Web

Trix supports all evergreen, self-updating desktop and mobile browsers.

Trix is built with emerging web standards, notably Custom Elements, Mutation Observer, and Promises. Eventually we expect all browsers to implement these standards. In the meantime, Trix includes polyfills for missing functionality.

Getting Started

Include the bundled

trix.css
and
trix.js
files in the
 of your page.

trix.css
includes default styles for the Trix toolbar, editor, and attachments. Skip this file if you prefer to define these styles yourself.

To use your own polyfills, or to target only browsers that support all of the required standards, include

trix-core.js
instead.

Creating an Editor

Place an empty

 tag on the page. Trix will automatically insert a separate 
 before the editor.

Like an HTML

, 
 accepts 
autofocus
and
placeholder
attributes. Unlike a
, 
 automatically expands vertically to fit its contents.

Integrating With Forms

To submit the contents of a

 with a form, first define a hidden input field in the form and assign it an 
id
. Then reference that
id
in the editor’s
input
attribute.

  
  


Trix will automatically update the value of the hidden input field with each change to the editor.

Populating With Stored Content

To populate a

 with stored content, include that content in the associated input element’s 
value
attribute.

  
  


Always use an associated input element to safely populate an editor. Trix won’t load any HTML content inside a

tag.

Styling Formatted Content

To ensure what you see when you edit is what you see when you save, use a CSS class name to scope styles for Trix formatted content. Apply this class name to your

 element, and to a containing element when you render stored Trix content for display in your application.
Stored content here

The default

trix.css
file includes styles for basic formatted content—including bulleted and numbered lists, code blocks, and block quotes—under the class name
trix-content
. We encourage you to use these styles as a starting point by copying them into your application’s CSS with a different class name.

Storing Attached Files

Trix automatically accepts files dragged or pasted into an editor and inserts them as attachments in the document. Each attachment is considered pending until you store it remotely and provide Trix with a permanent URL.

To store attachments, listen for the

trix-attachment-add
event. Upload the attached files with XMLHttpRequest yourself and set the attachment’s URL attribute upon completion. See the attachment example for detailed information.

If you don’t want to accept dropped or pasted files, call

preventDefault()
on the
trix-file-accept
event, which Trix dispatches just before the
trix-attachment-add
event.

Editing Text Programmatically

You can manipulate a Trix editor programmatically through the

Trix.Editor
interface, available on each
 element through its 
editor
property.
var element = document.querySelector("trix-editor")
element.editor  // is a Trix.Editor instance

Understanding the Document Model

The formatted content of a Trix editor is known as a document, and is represented as an instance of the

Trix.Document
class. To get the editor’s current document, use the
editor.getDocument
method.
element.editor.getDocument()  // is a Trix.Document instance

You can convert a document to an unformatted JavaScript string with the

document.toString
method.
var document = element.editor.getDocument()
document.toString()  // is a JavaScript string

Immutability and Equality

Documents are immutable values. Each change you make in an editor replaces the previous document with a new document. Capturing a snapshot of the editor’s content is as simple as keeping a reference to its document, since that document will never change over time. (This is how Trix implements undo.)

To compare two documents for equality, use the

document.isEqualTo
method.
var document = element.editor.getDocument()
document.isEqualTo(element.editor.getDocument())  // true

Getting and Setting the Selection

Trix documents are structured as sequences of individually addressable characters. The index of one character in a document is called a position, and a start and end position together make up a range.

To get the editor’s current selection, use the

editor.getSelectedRange
method, which returns a two-element array containing the start and end positions.
element.editor.getSelectedRange()  // [0, 0]

You can set the editor’s current selection by passing a range array to the

editor.setSelectedRange
method.
// Select the first character in the document
element.editor.setSelectedRange([0, 1])

Collapsed Selections

When the start and end positions of a range are equal, the range is said to be collapsed. In the editor, a collapsed selection appears as a blinking cursor rather than a highlighted span of text.

For convenience, the following calls to

setSelectedRange
are equivalent when working with collapsed selections:
element.editor.setSelectedRange(1)
element.editor.setSelectedRange([1])
element.editor.setSelectedRange([1, 1])

Directional Movement

To programmatically move the cursor or selection through the document, call the

editor.moveCursorInDirection
or
editor.expandSelectionInDirection
methods with a direction argument. The direction can be either
"forward"
or
"backward"
.
// Move the cursor backward one character
element.editor.moveCursorInDirection("backward")

// Expand the end of the selection forward by one character element.editor.expandSelectionInDirection("forward")

Converting Positions to Pixel Offsets

Sometimes you need to know the x and y coordinates of a character at a given position in the editor. For example, you might want to absolutely position a pop-up menu element below the editor’s cursor.

Call the

editor.getClientRectAtPosition
method with a position argument to get a
DOMRect
instance representing the left and top offsets, width, and height of the character at the given position.
var rect = element.editor.getClientRectAtPosition(0)
[rect.left, rect.top]  // [17, 49]

Inserting and Deleting Text

The editor interface provides methods for inserting, replacing, and deleting text at the current selection.

To insert or replace text, begin by setting the selected range, then call one of the insertion methods below. Trix will first remove any selected text, then insert the new text at the start position of the selected range.

Inserting Plain Text

To insert unformatted text into the document, call the

editor.insertString
method.
// Insert “Hello” at the beginning of the document
element.editor.setSelectedRange([0, 0])
element.editor.insertString("Hello")

Inserting HTML

To insert HTML into the document, call the

editor.insertHTML
method. Trix will first convert the HTML into its internal document model. During this conversion, any formatting that cannot be represented in a Trix document will be lost.
// Insert a bold “Hello” at the beginning of the document
element.editor.setSelectedRange([0, 0])
element.editor.insertHTML("Hello")

Inserting a File

To insert a DOM

File
object into the document, call the

editor.insertFile
method. Trix will insert a pending attachment for the file as if you had dragged and dropped it onto the editor.
// Insert the selected file from the first file input element
var file = document.querySelector("input[type=file]").file
element.editor.insertFile(file)

Inserting a Content Attachment

Content attachments are self-contained units of HTML that behave like files in the editor. They can be moved or removed, but not edited directly, and are represented by a single character position in the document model.

To insert HTML as an attachment, create a

Trix.Attachment
with a
content
attribute and call the
editor.insertAttachment
method. The HTML inside a content attachment is not subject to Trix’s document conversion rules and will be rendered as-is.
var attachment = new Trix.Attachment({ content: '@trix' })
element.editor.insertAttachment(attachment)

Inserting a Line Break

To insert a line break, call the

editor.insertLineBreak
method, which is functionally equivalent to pressing the return key.
// Insert “Hello\n”
element.editor.insertString("Hello")
element.editor.insertLineBreak()

Deleting Text

If the current selection is collapsed, you can simulate deleting text before or after the cursor with the

editor.deleteInDirection
method.
// “Backspace” the first character in the document
element.editor.setSelectedRange([1, 1])
element.editor.deleteInDirection("backward")

// Delete the second character in the document element.editor.setSelectedRange([1, 1]) element.editor.deleteInDirection("forward")

To delete a range of text, first set the selected range, then call

editor.deleteInDirection
with either direction as the argument.
// Delete the first five characters
element.editor.setSelectedRange([0, 4])
element.editor.deleteInDirection("forward")

Working With Attributes and Nesting

Trix represents formatting as sets of attributes applied across ranges of a document.

By default, Trix supports the inline attributes

bold
,
italic
,
href
, and
strike
, and the block-level attributes
heading1
,
quote
,
code
,
bullet
, and
number
.

Applying Formatting

To apply formatting to the current selection, use the

editor.activateAttribute
method.
element.editor.insertString("Hello")
element.editor.setSelectedRange([0, 5])
element.editor.activateAttribute("bold")

To set the

href
attribute, pass a URL as the second argument to
editor.activateAttribute
.
element.editor.insertString("Trix")
element.editor.setSelectedRange([0, 4])
element.editor.activateAttribute("href", "https://trix-editor.org/")

Removing Formatting

Use the

editor.deactivateAttribute
method to remove formatting from a selection.
element.editor.setSelectedRange([2, 4])
element.editor.deactivateAttribute("bold")

Formatting With a Collapsed Selection

If you activate or deactivate attributes when the selection is collapsed, your formatting changes will apply to the text inserted by any subsequent calls to

editor.insertString
.
element.editor.activateAttribute("italic")
element.editor.insertString("This is italic")

Adjusting the Nesting Level

To adjust the nesting level of quotes, bulleted lists, or numbered lists, call the

editor.increaseNestingLevel
and
editor.decreaseNestingLevel
methods.
element.editor.activateAttribute("quote")
element.editor.increaseNestingLevel()
element.editor.decreaseNestingLevel()

Using Undo and Redo

Trix editors support unlimited undo and redo. Successive typing and formatting changes are consolidated together at five-second intervals; all other input changes are recorded individually in undo history.

Call the

editor.undo
and
editor.redo
methods to perform an undo or redo operation.
element.editor.undo()
element.editor.redo()

Changes you make through the editor interface will not automatically record undo entries. You can save your own undo entries by calling the

editor.recordUndoEntry
method with a description argument.
element.editor.recordUndoEntry("Insert Text")
element.editor.insertString("Hello")

Loading and Saving Editor State

Serialize an editor’s state with

JSON.stringify
and restore saved state with the
editor.loadJSON
method. The serialized state includes the document and current selection, but does not include undo history.
// Save editor state to local storage
localStorage["editorState"] = JSON.stringify(element.editor)

// Restore editor state from local storage element.editor.loadJSON(JSON.parse(localStorage["editorState"]))

Observing Editor Changes

The

 element emits several events which you can use to observe and respond to changes in editor state.

  • trix-before-initialize
    fires when the
     element is attached to the DOM just before Trix installs its 
    editor
    object.
  • trix-initialize
    fires when the
     element is attached to the DOM and its 
    editor
    object is ready for use.
  • trix-change
    fires whenever the editor’s contents have changed.
  • trix-selection-change
    fires any time the selected range changes in the editor.
  • trix-focus
    and
    trix-blur
    fire when the editor gains or loses focus, respectively.
  • trix-file-accept
    fires when a file is dropped or inserted into the editor. You can access the DOM
    File
    object through the
    file
    property on the event. Call
    preventDefault
    on the event to prevent attaching the file to the document.
  • trix-attachment-add
    fires after an attachment is added to the document. You can access the Trix attachment object through the
    attachment
    property on the event. If the
    attachment
    object has a
    file
    property, you should store this file remotely and set the attachment’s URL attribute. See the attachment example for detailed information.
  • trix-attachment-remove
    fires when an attachment is removed from the document. You can access the Trix attachment object through the
    attachment
    property on the event. You may wish to use this event to clean up remotely stored files.

Contributing to Trix

Trix is open-source software, freely distributable under the terms of an MIT-style license. The source code is hosted on GitHub.

We welcome contributions in the form of bug reports, pull requests, or thoughtful discussions in the GitHub issue tracker. Please see the Code of Conduct for our pledge to contributors.

Trix was created by Javan Makhmali and Sam Stephenson, with development sponsored by Basecamp.

Building From Source

Trix is written in CoffeeScript and compiled to JavaScript with Blade.

From inside a checkout of the Trix Git repository, issue the following commands to build the distributable files in

dist/
:
$ bin/setup
$ bin/blade build

Developing In-Browser

You can spawn a development web server to work on Trix in a more convenient fashion. Instead of manually rebuilding the source each time, just reload a page in your browser to see your changes.

To develop in-browser, run

bin/setup
and follow the displayed instructions.

Running Tests

Make sure you’re set up to build from source using the instructions above. Then run

bin/blade runner
and visit the displayed URL to run the Trix test suite.

Pull Requests

Only commit changes to Trix’s source (everything except the compiled files in

/dist
) and leave the VERSION unchanged. We update both when publishing new releases. :heart:

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