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<!DOCTYPE html>
<html>
<head>
<title></title>
<script src="carota-debug.js"></script>
<style>
#exampleToolbar {
position: absolute;
left: 10px;
top: 10px;
right: 10px;
height: 27px;
overflow: hidden;
}
#exampleToolbar label {
border: 1px solid silver;
padding: 1px 2px 0 1px;
}
#exampleEditor {
border: 1px solid silver;
position: absolute;
left: 10px;
top: 40px;
right: 50%;
bottom: 40px;
}
#examplePersistence {
position: absolute;
top: 40px;
width: 50%;
right: 0;
bottom: 40px;
}
#examplePersistence div {
position: absolute;
left: 10px;
top: 0;
right: 10px;
bottom: 0;
overflow: hidden;
}
#examplePersistence textarea {
width: 99%;
height: 99%;
border: none;
background: rgb(30, 30, 30);
color: rgb(0, 200, 20);
}
#pageLinks {
position: absolute;
left: 10px;
height: 20px;
right: 10px;
bottom: 10px;
overflow: hidden;
text-align: center;
font-family: sans-serif;
}
button img {
width: 12px;
height: 12px;
}
.editablePage {
display: none
}
</style>
</head>
<body>
<div id="exampleToolbar">
<select id="font">
<option value="serif">Times</option>
<option value="sans-serif">Helvetica</option>
<option value="monospace">Courier</option>
<option value="cursive">Cursive</option>
<option value="fantasy">Fantasy</option>
</select>
<select id="size">
<option>8</option>
<option>9</option>
<option>10</option>
<option>11</option>
<option>12</option>
<option>14</option>
<option>16</option>
<option>18</option>
<option>20</option>
<option>24</option>
<option>30</option>
<option>36</option>
<option>72</option>
</select>
<label><input type="checkbox" id="bold"><strong>B</strong></label>
<label><input type="checkbox" id="italic"><em>i</em></label>
<label><input type="checkbox" id="underline"><u>u</u></label>
<label><input type="checkbox" id="strikeout"><strike>s</strike></label>
<select id="align">
<option value="left">Left</option>
<option value="center">Center</option>
<option value="right">Right</option>
<option value="justify">Justify</option>
</select>
<select id="script">
<option value="normal">Normal</option>
<option value="super">Superscript</option>
<option value="sub">Subscript</option>
</select>
<select id="color">
<option value="black">Black</option>
<option value="red">Red</option>
<option value="green">Green</option>
<option value="blue">Blue</option>
</select>
<button id="smiley"><img src="smiley.png"></button>
<button id="undo">Undo</button>
<button id="redo">Redo</button>
</div>
<div id="exampleEditor"></div>
<div id="examplePersistence">
<div>
<textarea></textarea>
</div>
</div>
<div id="pageLinks">
<a href="#welcome">Welcome!</a> |
<a href="#why">Why?</a> |
<a href="#how">How does it work?</a> |
<a href="#usage">Usage</a> |
<a href="http://github.com/danielearwicker/carota">Source on Github</a>
</div>
<div class="editablePage" id="welcome">
<h1>Welcome!</h1>
<br>
<p>You've found the demo page for <span class="carota">Carota</span>, a rich text editor
implemented entirely in JavaScript that uses HTML5 Canvas for rendering. Most in-browser
editors use a built-in feature called <code>contentEditable</code> to do most of the
hard work, but this has some limitations and drawbacks that are just too much for more
sensitive people, like me, to bear, so I decided to start from scratch.
(Anyway, it's fun to write your own editor!)
</p>
<br>
<p>The source code is released under the very permissive <strong>MIT license</strong>,
so you can do pretty much anything you want with it.
</p>
<br>
<p>At runtime Carota has <em>no external dependencies</em>. You just pull in the
carota-min.js file using the SCRIPT tag and away you go. Or else get node and use:
</p>
<br>
<p>
<code>npm install carota</code>
</p>
<br>
<p>to get the full source, including this demo site. By the way,
<span class="carota">Carota</span> itself is displaying all this text, meaning that
you can play with the editor right now! Try <code>Ctrl+A</code> and then
<code>Backspace</code> to clear this document and see how the JSON view on the right
changes as you make further edits. Press <code>Ctrl+Z</code> to undo your changes.
</p>
<br>
<p><strong>Click the links below for more information...</strong><p>
</p>
</div>
<div class="editablePage" id="why">
<h1>Why might you need this?</h1>
<br>
<p>For many people's needs, the <code>contentEditable</code> attribute in modern browsers is
quite adequate. But if you need more control over rich text editing it is sadly a dead
end.</p>
<br>
<p>The word processor in <b>Google Docs</b> does not use
<code>contentEditable</code>.
Nor does <b>Apple's Pages in iCloud</b>. Instead they have their own JavaScript-based
rich text rendering and editing code. Sadly they are not open source licensed!
</p>
<br>
<p>In some ways, <code>contentEditable</code> is too powerful. It allows your users to edit
every possible feature of HTML implemented by the browser. I often find that I only want
to support a simple form of rich text that is totally under my control. And the API for
representing a range within the text is quite complex because it has to deal with the
tree-like nature of the DOM. I wish there was a simple way to work in pure character
positions (i.e. mere integers).
</p>
<br>
<p>In other ways, <code>contentEditable</code> is frustratingly inadequate. There are built-in
commands for applying formatting changes to the current selection, but they <em>suck</em>,
especially setting the font size. There are bugs and quirks that vary between browsers.
Taming <code>contentEditable</code> can become a full-time job in itself.
</p>
<br>
<p>Bear in mind that <span class="carota">Carota</span> does not implement all the same
features as HTML's <code>contentEditable</code>. If you're okay with the limitations of
<code>contentEditable</code> then by all means you should stick with it.
</p>
</div>
<div class="editablePage" id="how">
<h1>How does it work?</h1>
<br>
<p>Several representations of text play a part in <span class="carota">Carota</span>.</p>
<br>
<p><b>JSON</b> is the cornerstone of persistence in JavaScript. It is used here to
represent rich text, which is just an array of objects. Each object is called a
<i>run</i>, and has a property called <code>text</code> and various other optional
properties to specify the formatting for the text in the run. The text can include
inline objects of your own invention, which you can tell
<span class="carota">Carota</span> how to represent. (That's how the smiley icons
work in this demo - try inserting one!)
</p>
<br>
<p><b>Characters</b> are objects representing the characters in the text as a single
continuous stream of objects. This is an abstraction over the JSON format to make
it easy to split the text into words. An inline object acts like a single character.
</p>
<br>
<p><b>Words</b> are objects representing the words in the text, the output of the
word-breaking process. A word has two parts: the non-space characters, and the
trailing space characters. Either part may be empty, but not both. (A new line is
always emitted as a separate word.) Of course, a word can contain regions of the
text with different formatting. All edits to the document involve modifying the
list of words. Words store their own dimensions (<code>width</code>,
<code>ascent</code> and <code>descent</code>).
</p>
<br>
<p><b>Static</b> representation is the result of word-wrapping. Every time the word
list is modified, wrapping must be performed, but it's pretty fast because we
already know the dimensions of each word. The static representation is a list
of <code>Line</code> objects, and each line contains a list of
<code>PositionedWord</code> objects, each of which contains a list of
<code>PositionedCharacter</code> objects. These objects form a uniform hierarchy
of nodes, and at the root is the <code>Document</code>. Everything is already
positioned, so drawing to the canvas is fast, and implementing the editor is
pretty easy. Also any custom inline objects are converted into handlers that
know how to render them.
</p>
<br>
<p>Those are the main core representations involved. In addition a subset of
<b>HTML</b> can be loaded into the editor via a parser that converts it into the
native JSON format.
</p>
</div>
<div class="editablePage" id="usage">
<h1>How to use it</h1>
<br>
<p>First, the bad news: if you need to support IE8 and earlier, then
<span class="carota">Carota</span> is not for you. Right now it requires
Canvas. It may be extended in the future to support other ways of rendering.</p>
<br>
<p>This demo page has been deliberately set up to make it easy to learn from,
the old fashioned way: using the <em>View source</em> command. Everything is
in a single index.html file.</p>
<br>
<p>It begins with some basic CSS styling, mostly for positioning. Then there
is the HTML, most of which is for the "toolbar". <span class="carota">Carota</span>
does not have a built-in toolbar, but it's very easy to wire up your own
controls to it. This page does it in about 30 lines of code.</p>
<br>
<p>The text for these pages is held in some hidden DIVs, which get parsed
into the native JSON format and then loaded into the editor.</p>
<br>
<p>Finally there is a PRE element that displays the JSON saved from the editor,
every time you make an edit.</p>
<br>
<p>The parts of the code that interact with <span class="carota">Carota</span>
(there isn't much) works by calling <code>carota.editor.create</code> to cause the
editor to be created. Then methods are called on the resulting object to
<code>load</code> this text, to subscribe to events (<code>selectionChanged</code>,
<code>contentChanged</code>), to <code>performUndo</code> (and discover if we
<code>canUndo</code>), to query or modify the <code>selectedRange</code> and to
<code>insert</code> inline elements (the smiley button).</p>
<br>
<p>There are also a handful of calls to functions in <code>carota.dom</code> which
is just a very minimal helper library for conveniently wiring up events, etc. In
your own code you'll probably want to use a more full-featured alternative like
jQuery, etc. <span class="carota">Carota</span> deliberately avoids depending on
any such general DOM-manipulation library so it can integrate with anything.
</p>
</div>
<script>
window.onload = function() {
var elem = document.querySelector('#exampleEditor');
var exampleEditor = carota.editor.create(elem);
// Set up our custom inline - a smiley emoji
var smiley = document.querySelector('#smiley img');
exampleEditor.customCodes = function(obj) {
if (obj.smiley) {
// Must return an object that encapsulates the inline
return {
// measure: must return width, ascent and descent
measure: function(/*formatting*/) {
return {
width: 24,
ascent: 24,
descent: 0
};
},
// draw: implements the appearance of the inline on canvas
draw: function(ctx, x, y, width, ascent, descent, formatting) {
ctx.drawImage(smiley, x, y - ascent, width, ascent);
}
}
}
};
// Setting up the button so user can insert a smiley
carota.dom.handleEvent(document.querySelector('#smiley'), 'click', function() {
exampleEditor.insert({ smiley: true });
});
// Wire up undo/redo commands
var undo = document.querySelector('#undo'),
redo = document.querySelector('#redo');
carota.dom.handleEvent(undo, 'click', function() {
exampleEditor.performUndo(false);
});
carota.dom.handleEvent(redo, 'click', function() {
exampleEditor.performUndo(true);
});
var updateUndo = function() {
undo.disabled = !exampleEditor.canUndo(false);
redo.disabled = !exampleEditor.canUndo(true);
};
// Wire up the toolbar controls
['font', 'size', 'bold', 'italic', 'underline',
'strikeout', 'align', 'script', 'color'].forEach(function(id) {
var elem = document.querySelector('#' + id);
// When the control changes value, update the selected range's formatting
carota.dom.handleEvent(elem, 'change', function() {
var range = exampleEditor.selectedRange();
var val = elem.nodeName === 'INPUT' ? elem.checked : elem.value;
range.setFormatting(id, val);
});
// When the selected range coordinates change, update the control
exampleEditor.selectionChanged(function(getFormatting) {
var formatting = getFormatting();
var val = id in formatting ? formatting[id] : carota.runs.defaultFormatting[id];
if (elem.nodeName === 'INPUT') {
if (val === carota.runs.multipleValues) {
elem.indeterminate = true;
} else {
elem.indeterminate = false;
elem.checked = val;
}
} else {
elem.value = val;
}
});
});
// We don't update the JSON view until half a second after the last change
// to avoid slowing things down too much
var persistenceTextArea = document.querySelector('#examplePersistence textarea');
var updateTimer = null;
var updatePersistenceView = function() {
if (updateTimer !== null) {
clearTimeout(updateTimer);
}
updateTimer = setTimeout(function() {
updateTimer = null;
persistenceTextArea.value = JSON.stringify(exampleEditor.save(), null, 4);
}, 500);
};
var manuallyChangingJson = 0;
carota.dom.handleEvent(persistenceTextArea, 'input', function() {
try {
manuallyChangingJson++;
exampleEditor.load(JSON.parse(persistenceTextArea.value), false);
} catch (x) {
// ignore if syntax errors
} finally {
manuallyChangingJson--;
}
});
// Whenever the document changes, re-display the JSON format and update undo buttons
exampleEditor.contentChanged(function() {
updateUndo();
if (!manuallyChangingJson) {
updatePersistenceView();
}
});
// Load one of the hidden chunks of HTML
var load = function(selector) {
var html = document.querySelector(selector);
if (html) {
var runs = carota.html.parse(html, {
carota: { color: 'orange', bold: true, size: 14 }
});
exampleEditor.load(runs);
}
};
// Set up the page links so they call load
var pageLinks = document.querySelectorAll('#pageLinks a');
for (var n = 0; n < pageLinks.length; n++) {
(function() {
var pageLink = pageLinks[n];
var ref = pageLink.attributes['href'].value;
if (ref[0] === '#') {
carota.dom.handleEvent(pageLink, 'click', function() {
load(ref);
return false;
});
}
})();
}
load('#welcome');
/*exampleEditor.load([
{ text: 'A' },
{ text: { $: 'listStart' }, color: 'blue' },
{ text: 'B' },
{ text: { $: 'listNext' }, color: 'red' },
{ text: 'C' },
{ text: { $: 'listEnd' } },
{ text: 'D' }
]);
*/
};
</script>
</body>
</html>