For a project of mine I would love to provide auto completion for a specific textarea. Similar to how intellisense/omnicomplete works. For that however I have to find out the absolute cursor position so that I know where the DIV should appear.
Turns out: that's (nearly I hope) impossible to achieve. Does anyone has some neat ideas how to solve that problem?
Version 2 of My Hacky Experiment
This new version works with any font, which can be adjusted on demand, and any textarea size.
After noticing that some of you are still trying to get this to work, I decided to try a new approach. My results are FAR better this time around - at least on google chrome on linux. I no longer have a windows PC available to me, so I can only test on chrome / firefox on Ubuntu. My results work 100% consistently on Chrome, and let's say somewhere around 70 - 80% on Firefox, but I don't imagine it would be incredibly difficult to find the inconsistencies.
This new version relies on a Canvas object. In my example, I actually show that very canvas - just so you can see it in action, but it could very easily be done with a hidden canvas object.
This is most certainly a hack, and I apologize ahead of time for my rather thrown together code. At the very least, in google chrome, it works consistently, no matter what font I set it to, or size of textarea. I used Sam Saffron's example to show cursor coordinates (a gray-background div). I also added a "Randomize" link, so you can see it work in different font / texarea sizes and styles, and watch the cursor position update on the fly. I recommend looking at the full page demo so you can better see the companion canvas play along.
I'll summarize how it works...
The underlying idea is that we're trying to redraw the textarea on a canvas, as closely as possible. Since the browser uses the same font engine for both and texarea, we can use canvas's font measurement functionality to figure out where things are. From there, we can use the canvas methods available to us to figure out our coordinates.
First and foremost, we adjust our canvas to match the dimensions of the textarea. This is entirely for visual purposes since the canvas size doesn't really make a difference in our outcome. Since Canvas doesn't actually provide a means of word wrap, I had to conjure (steal / borrow / munge together) a means of breaking up lines to as-best-as-possible match the textarea. This is where you'll likely find you need to do the most cross-browser tweaking.
After word wrap, everything else is basic math. We split the lines into an array to mimic the word wrap, and now we want to loop through those lines and go all the way down until the point where our current selection ends. In order to do that, we're just counting characters and once we surpass selection.end, we know we have gone down far enough. Multiply the line count up until that point with the line-height and you have a y coordinate.
The x coordinate is very similar, except we're using context.measureText. As long as we're printing out the right number of characters, that will give us the width of the line that's being drawn to Canvas, which happens to end after the last character written out, which is the character before the currentl selection.end position.
When trying to debug this for other browsers, the thing to look for is where the lines don't break properly. You'll see in some places that the last word on a line in canvas may have wrapped over on the textarea or vice-versa. This has to do with how the browser handles word wraps. As long as you get the wrapping in the canvas to match the textarea, your cursor should be correct.
I'll paste the source below. You should be able to copy and paste it, but if you do, I ask that you download your own copy of jquery-fieldselection instead of hitting the one on my server.
I've also upped a new demo as well as a fiddle.
Good luck!
<!DOCTYPE html>
<html lang="en-US">
<head>
<meta charset="utf-8" />
<title>Tooltip 2</title>
<script type="text/javascript" src="//ajax.googleapis.com/ajax/libs/jquery/1.8.2/jquery.min.js"></script>
<script type="text/javascript" src="http://enobrev.info/cursor/js/jquery-fieldselection.js"></script>
<style type="text/css">
form {
float: left;
margin: 20px;
}
#textariffic {
height: 400px;
width: 300px;
font-size: 12px;
font-family: 'Arial';
line-height: 12px;
}
#tip {
width:5px;
height:30px;
background-color: #777;
position: absolute;
z-index:10000
}
#mock-text {
float: left;
margin: 20px;
border: 1px inset #ccc;
}
/* way the hell off screen */
.scrollbar-measure {
width: 100px;
height: 100px;
overflow: scroll;
position: absolute;
top: -9999px;
}
#randomize {
float: left;
display: block;
}
</style>
<script type="text/javascript">
var oCanvas;
var oTextArea;
var $oTextArea;
var iScrollWidth;
$(function() {
iScrollWidth = scrollMeasure();
oCanvas = document.getElementById('mock-text');
oTextArea = document.getElementById('textariffic');
$oTextArea = $(oTextArea);
$oTextArea
.keyup(update)
.mouseup(update)
.scroll(update);
$('#randomize').bind('click', randomize);
update();
});
function randomize() {
var aFonts = ['Arial', 'Arial Black', 'Comic Sans MS', 'Courier New', 'Impact', 'Times New Roman', 'Verdana', 'Webdings'];
var iFont = Math.floor(Math.random() * aFonts.length);
var iWidth = Math.floor(Math.random() * 500) + 300;
var iHeight = Math.floor(Math.random() * 500) + 300;
var iFontSize = Math.floor(Math.random() * 18) + 10;
var iLineHeight = Math.floor(Math.random() * 18) + 10;
var oCSS = {
'font-family': aFonts[iFont],
width: iWidth + 'px',
height: iHeight + 'px',
'font-size': iFontSize + 'px',
'line-height': iLineHeight + 'px'
};
console.log(oCSS);
$oTextArea.css(oCSS);
update();
return false;
}
function showTip(x, y) {
$('#tip').css({
left: x + 'px',
top: y + 'px'
});
}
// https://stackoverflow.com/a/11124580/14651
// https://stackoverflow.com/a/3960916/14651
function wordWrap(oContext, text, maxWidth) {
var aSplit = text.split(' ');
var aLines = [];
var sLine = "";
// Split words by newlines
var aWords = [];
for (var i in aSplit) {
var aWord = aSplit[i].split('\n');
if (aWord.length > 1) {
for (var j in aWord) {
aWords.push(aWord[j]);
aWords.push("\n");
}
aWords.pop();
} else {
aWords.push(aSplit[i]);
}
}
while (aWords.length > 0) {
var sWord = aWords[0];
if (sWord == "\n") {
aLines.push(sLine);
aWords.shift();
sLine = "";
} else {
// Break up work longer than max width
var iItemWidth = oContext.measureText(sWord).width;
if (iItemWidth > maxWidth) {
var sContinuous = '';
var iWidth = 0;
while (iWidth <= maxWidth) {
var sNextLetter = sWord.substring(0, 1);
var iNextWidth = oContext.measureText(sContinuous + sNextLetter).width;
if (iNextWidth <= maxWidth) {
sContinuous += sNextLetter;
sWord = sWord.substring(1);
}
iWidth = iNextWidth;
}
aWords.unshift(sContinuous);
}
// Extra space after word for mozilla and ie
var sWithSpace = (jQuery.browser.mozilla || jQuery.browser.msie) ? ' ' : '';
var iNewLineWidth = oContext.measureText(sLine + sWord + sWithSpace).width;
if (iNewLineWidth <= maxWidth) { // word fits on current line to add it and carry on
sLine += aWords.shift() + " ";
} else {
aLines.push(sLine);
sLine = "";
}
if (aWords.length === 0) {
aLines.push(sLine);
}
}
}
return aLines;
}
// http://davidwalsh.name/detect-scrollbar-width
function scrollMeasure() {
// Create the measurement node
var scrollDiv = document.createElement("div");
scrollDiv.className = "scrollbar-measure";
document.body.appendChild(scrollDiv);
// Get the scrollbar width
var scrollbarWidth = scrollDiv.offsetWidth - scrollDiv.clientWidth;
// Delete the DIV
document.body.removeChild(scrollDiv);
return scrollbarWidth;
}
function update() {
var oPosition = $oTextArea.position();
var sContent = $oTextArea.val();
var oSelection = $oTextArea.getSelection();
oCanvas.width = $oTextArea.width();
oCanvas.height = $oTextArea.height();
var oContext = oCanvas.getContext("2d");
var sFontSize = $oTextArea.css('font-size');
var sLineHeight = $oTextArea.css('line-height');
var fontSize = parseFloat(sFontSize.replace(/[^0-9.]/g, ''));
var lineHeight = parseFloat(sLineHeight.replace(/[^0-9.]/g, ''));
var sFont = [$oTextArea.css('font-weight'), sFontSize + '/' + sLineHeight, $oTextArea.css('font-family')].join(' ');
var iSubtractScrollWidth = oTextArea.clientHeight < oTextArea.scrollHeight ? iScrollWidth : 0;
oContext.save();
oContext.clearRect(0, 0, oCanvas.width, oCanvas.height);
oContext.font = sFont;
var aLines = wordWrap(oContext, sContent, oCanvas.width - iSubtractScrollWidth);
var x = 0;
var y = 0;
var iGoal = oSelection.end;
aLines.forEach(function(sLine, i) {
if (iGoal > 0) {
oContext.fillText(sLine.substring(0, iGoal), 0, (i + 1) * lineHeight);
x = oContext.measureText(sLine.substring(0, iGoal + 1)).width;
y = i * lineHeight - oTextArea.scrollTop;
var iLineLength = sLine.length;
if (iLineLength == 0) {
iLineLength = 1;
}
iGoal -= iLineLength;
} else {
// after
}
});
oContext.restore();
showTip(oPosition.left + x, oPosition.top + y);
}
</script>
</head>
<body>
<a href="#" id="randomize">Randomize</a>
<form id="tipper">
<textarea id="textariffic">Aliquam urna. Nullam augue dolor, tincidunt condimentum, malesuada quis, ultrices at, arcu. Aliquam nunc pede, convallis auctor, sodales eget, aliquam eget, ligula. Proin nisi lacus, scelerisque nec, aliquam vel, dictum mattis, eros. Curabitur et neque. Fusce sollicitudin. Quisque at risus. Suspendisse potenti. Mauris nisi. Sed sed enim nec dui viverra congue. Phasellus velit sapien, porttitor vitae, blandit volutpat, interdum vel, enim. Cras sagittis bibendum neque. Proin eu est. Fusce arcu. Aliquam elit nisi, malesuada eget, dignissim sed, ultricies vel, purus. Maecenas accumsan diam id nisi.
Phasellus et nunc. Vivamus sem felis, dignissim non, lacinia id, accumsan quis, ligula. Pellentesque habitant morbi tristique senectus et netus et malesuada fames ac turpis egestas. Sed scelerisque nulla sit amet mi. Nulla consequat, elit vitae tempus vulputate, sem libero rhoncus leo, vulputate viverra nulla purus nec turpis. Nam turpis sem, tincidunt non, congue lobortis, fermentum a, ipsum. Nulla facilisi. Aenean facilisis. Maecenas a quam eu nibh lacinia ultricies. Morbi malesuada orci quis tellus.
Sed eu leo. Donec in turpis. Donec non neque nec ante tincidunt posuere. Pellentesque blandit. Ut vehicula vestibulum risus. Maecenas commodo placerat est. Integer massa nunc, luctus at, accumsan non, pulvinar sed, odio. Pellentesque eget libero iaculis dui iaculis vehicula. Curabitur quis nulla vel felis ullamcorper varius. Sed suscipit pulvinar lectus.</textarea>
</form>
<div id="tip"></div>
<canvas id="mock-text"></canvas>
</body>
</html>
Bug
There's one bug I do recall. If you put the cursor before the first letter on a line, it shows the "position" as the last letter on the previous line. This has to do with how selection.end work. I don't think it should be too difficult to look for that case and fix it accordingly.
Version 1
Leaving this here so you can see the progress without having to dig through the edit history.
It's not perfect and it's most Definitely a hack, but I got it to work pretty well on WinXP IE, FF, Safari, Chrome and Opera.
As far as I can tell there's no way to directly find out the x/y of a cursor on any browser. The IE method, mentioned by Adam Bellaire is interesting, but unfortunately not cross-browser. I figured the next best thing would be to use the characters as a grid.
Unfortunately there's no font metric information built into any of the browsers, which means a monospace font is the only font type that's going to have a consistent measurement. Also, there's no reliable means of figuring out a font-width from the font-height. At first I'd tried using a percentage of the height, which worked great. Then I changed the font-size and everything went to hell.
I tried one method to figure out character width, which was to create a temporary textarea and keep adding characters until the scrollHeight (or scrollWidth) changed. It seems plausable, but about halfway down that road, I realized I could just use the cols attribute on the textarea and figured there are enough hacks in this ordeal to add another one. This means you can't set the width of the textarea via css. You HAVE to use the cols for this to work.
The next problem I ran into is that, even when you set the font via css, the browsers report the font differently. When you don't set a font, mozilla uses monospace by default, IE uses Courier New, Opera "Courier New" (with quotes), Safari, 'Lucida Grand' (with single quotes). When you do set the font to monospace, mozilla and ie take what you give them, Safari comes out as -webkit-monospace and Opera stays with "Courier New".
So now we initialize some vars. Make sure to set your line height in the css as well. Firefox reports the correct line height, but IE was reporting "normal" and I didn't bother with the other browsers. I just set the line height in my css and that resolved the difference. I haven't tested with using ems instead of pixels. Char height is just font size. Should probably pre-set that in your css as well.
Also, one more pre-setting before we start placing characters - which really had me scratching my head. For ie and mozilla, texarea chars are < cols, everything else is <= chars. So Chrome can fit 50 chars across, but mozilla and ie would break the last word off the line.
Now we're going to create an array of first-character positions for every line. We loop through every char in the textarea. If it's a newline, we add a new position to our line array. If it's a space, we try to figure out if the current "word" will fit on the line we're on or if it's going to get pushed to the next line. Punctuation counts as a part of the "word". I haven't tested with tabs, but there's a line there for adding 4 chars for a tab char.
Once we have an array of line positions, we loop through and try to find which line the cursor is on. We're using hte "End" of the selection as our cursor.
x = (cursor position - first character position of cursor line) * character width
y = ((cursor line + 1) * line height) - scroll position
I'm using jquery 1.2.6, jquery-fieldselection, and jquery-dimensions
The Demo: http://enobrev.info/cursor/
And the code:
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
<title>Tooltip</title>
<script type="text/javascript" src="js/jquery-1.2.6.js"></script>
<script type="text/javascript" src="js/jquery-fieldselection.js"></script>
<script type="text/javascript" src="js/jquery.dimensions.js"></script>
<style type="text/css">
form {
margin: 20px auto;
width: 500px;
}
#textariffic {
height: 400px;
font-size: 12px;
font-family: monospace;
line-height: 15px;
}
#tip {
position: absolute;
z-index: 2;
padding: 20px;
border: 1px solid #000;
background-color: #FFF;
}
</style>
<script type="text/javascript">
$(function() {
$('textarea')
.keyup(update)
.mouseup(update)
.scroll(update);
});
function showTip(x, y) {
y = y + $('#tip').height();
$('#tip').css({
left: x + 'px',
top: y + 'px'
});
}
function update() {
var oPosition = $(this).position();
var sContent = $(this).val();
var bGTE = jQuery.browser.mozilla || jQuery.browser.msie;
if ($(this).css('font-family') == 'monospace' // mozilla
|| $(this).css('font-family') == '-webkit-monospace' // Safari
|| $(this).css('font-family') == '"Courier New"') { // Opera
var lineHeight = $(this).css('line-height').replace(/[^0-9]/g, '');
lineHeight = parseFloat(lineHeight);
var charsPerLine = this.cols;
var charWidth = parseFloat($(this).innerWidth() / charsPerLine);
var iChar = 0;
var iLines = 1;
var sWord = '';
var oSelection = $(this).getSelection();
var aLetters = sContent.split("");
var aLines = [];
for (var w in aLetters) {
if (aLetters[w] == "\n") {
iChar = 0;
aLines.push(w);
sWord = '';
} else if (aLetters[w] == " ") {
var wordLength = parseInt(sWord.length);
if ((bGTE && iChar + wordLength >= charsPerLine)
|| (!bGTE && iChar + wordLength > charsPerLine)) {
iChar = wordLength + 1;
aLines.push(w - wordLength);
} else {
iChar += wordLength + 1; // 1 more char for the space
}
sWord = '';
} else if (aLetters[w] == "\t") {
iChar += 4;
} else {
sWord += aLetters[w];
}
}
var iLine = 1;
for(var i in aLines) {
if (oSelection.end < aLines[i]) {
iLine = parseInt(i) - 1;
break;
}
}
if (iLine > -1) {
var x = parseInt(oSelection.end - aLines[iLine]) * charWidth;
} else {
var x = parseInt(oSelection.end) * charWidth;
}
var y = (iLine + 1) * lineHeight - this.scrollTop; // below line
showTip(oPosition.left + x, oPosition.top + y);
}
}
</script>
</head>
<body>
<form id="tipper">
<textarea id="textariffic" cols="50">
Aliquam urna. Nullam augue dolor, tincidunt condimentum, malesuada quis, ultrices at, arcu. Aliquam nunc pede, convallis auctor, sodales eget, aliquam eget, ligula. Proin nisi lacus, scelerisque nec, aliquam vel, dictum mattis, eros. Curabitur et neque. Fusce sollicitudin. Quisque at risus. Suspendisse potenti. Mauris nisi. Sed sed enim nec dui viverra congue. Phasellus velit sapien, porttitor vitae, blandit volutpat, interdum vel, enim. Cras sagittis bibendum neque. Proin eu est. Fusce arcu. Aliquam elit nisi, malesuada eget, dignissim sed, ultricies vel, purus. Maecenas accumsan diam id nisi.
Phasellus et nunc. Vivamus sem felis, dignissim non, lacinia id, accumsan quis, ligula. Pellentesque habitant morbi tristique senectus et netus et malesuada fames ac turpis egestas. Sed scelerisque nulla sit amet mi. Nulla consequat, elit vitae tempus vulputate, sem libero rhoncus leo, vulputate viverra nulla purus nec turpis. Nam turpis sem, tincidunt non, congue lobortis, fermentum a, ipsum. Nulla facilisi. Aenean facilisis. Maecenas a quam eu nibh lacinia ultricies. Morbi malesuada orci quis tellus.
Sed eu leo. Donec in turpis. Donec non neque nec ante tincidunt posuere. Pellentesque blandit. Ut vehicula vestibulum risus. Maecenas commodo placerat est. Integer massa nunc, luctus at, accumsan non, pulvinar sed, odio. Pellentesque eget libero iaculis dui iaculis vehicula. Curabitur quis nulla vel felis ullamcorper varius. Sed suscipit pulvinar lectus.
</textarea>
</form>
<p id="tip">Here I Am!!</p>
</body>
</html>
I won't explain the problems related to this stuff again because they are well explained in other posts. Just will point a possible solution, it has some bug but it's a starting point.
Fortunately there is a scrip on Github to calculate the caret position relative to it's container, but it requires jQuery. GitHub page here: jquery-caret-position-getter, Thanxs to Bevis.Zhao.
Based on it I have implemented the next code: check it in action here in jsFiddle.net
<html><head>
<meta http-equiv="content-type" content="text/html; charset=UTF-8">
<title>- jsFiddle demo by mjerez</title>
<script type="text/javascript" src="http://code.jquery.com/jquery-1.8.2.js"></script>
<link rel="stylesheet" type="text/css" href="http://jsfiddle.net/css/normalize.css">
<link rel="stylesheet" type="text/css" href="http://jsfiddle.net/css/result-light.css">
<script type="text/javascript" src="https://raw.github.com/beviz/jquery-caret-position-getter/master/jquery.caretposition.js"></script>
<style type="text/css">
body{position:relative;font:normal 100% Verdana, Geneva, sans-serif;padding:10px;}
.aux{background:#ccc;opacity: 0.5;width:50%;padding:5px;border:solid 1px #aaa;}
.hidden{display:none}
.show{display:block; position:absolute; top:0px; left:0px;}
</style>
<script type="text/javascript">//<![CDATA[
$(document).keypress(function(e) {
if ($(e.target).is('input, textarea')) {
var key = String.fromCharCode(e.which);
var ctrl = e.ctrlKey;
if (ctrl) {
var display = $("#autocomplete");
var editArea = $('#editArea');
var pos = editArea.getCaretPosition();
var offset = editArea.offset();
// now you can use left, top(they are relative position)
display.css({
left: offset.left + pos.left,
top: offset.top + pos.top,
color : "#449"
})
display.toggleClass("show");
return false;
}
}
});
window.onload = (function() {
$("#editArea").blur(function() {
if ($("#autocomplete").hasClass("show")) $("#autocomplete").toggleClass("show");
})
});
//]]>
</script>
</head>
<body>
<p>Click ctrl+space to while you write to diplay the autocmplete pannel.</p>
</br>
<textarea id="editArea" rows="4" cols="50"></textarea>
</br>
</br>
</br>
<div id="autocomplete" class="aux hidden ">
<ol>
<li>Option a</li>
<li>Option b</li>
<li>Option c</li>
<li>Option d</li>
</ol>
</div>
</body>
Note that this question is a duplicate of a one asked a month earlier, and I've answered it here. I'll only maintain the answer at that link, since this question should have been closed as duplicate years ago.
I've looked for a textarea caret coordinates plugin for meteor-autocomplete, so I've evaluated all the 8 plugins on GitHub. The winner is, by far, textarea-caret-position from Component.
A mirror <div> is created off-screen and styled exactly like the <textarea>. Then, the text of the textarea up to the caret is copied into the div and a <span> is inserted right after it. Then, the text content of the span is set to the remainder of the text in the textarea, in order to faithfully reproduce the wrapping in the faux div.
This is the only method guaranteed to handle all the edge cases pertaining to wrapping long lines. It's also used by GitHub to determine the position of its @ user dropdown.
I posted a topic related to this problem on a Russian JavaScript site.
If you don't understand Russian try translated by Google version: http://translate.google.ru/translate?js=y&prev=_t&hl=ru&ie=UTF-8&layout=1&eotf=1&u=http://javascript.ru/forum/events/7771-poluchit-koordinaty-kursora-v-tekstovom-pole-v-pikselyakh.html&sl=ru&tl=en
Thre is some markup issues in the code examples in translated version so you can read the code in the original Russian post.
The idea is simple. There is no easy, universal and cross-browser method to get cursor position in pixels. Frankly speaking there is, but only for Internet Explorer.
In other browsers if you do really need to calculate it you have to ...
This blog appears to be close too answering the question. I haven't tried it my self, but author says its tested with FF3, Chrome, IE, Opera, Safari. Code is on GitHub
fixed it here: http://jsfiddle.net/eMwKd/4/
only downside is that the already provided function getCaret() resolves to the wrong position on key down. therefor the red cursor seems to be behind the real cursor unless you release the key.
I will have another look into it.
update: hm, word-wrapping is not accurate if lines too long..
This blog post seems to address your question, but unfortunately the author admits he has only tested it in IE 6.
The DOM in IE does not provide information regarding relative position in terms of characters; however, it does provide bounding and offset values for browser-rendered controls. Thus, I used these values to determine the relative bounds of a character. Then, using the JavaScript TextRange, I created a mechanism for working with such measures to calculate the Line and Column position for fixed-width fonts within a given TextArea.
First, the relative bounds for the TextArea must be calculated based upon the size of the fixed-width font used. To do this, the original value of the TextArea must be stored in a local JavaScript variable and clear the value. Then, a TextRange is created to determine the Top and Left bounds of the TextArea.
I don't know a solution for textarea but it sure works for a div with contenteditable.
You can use the Range API. Like so: (yes, you really only need just these 3 lines of code)
// get active selection
var selection = window.getSelection();
// get the range (you might want to check selection.rangeCount
// to see if it's popuplated)
var range = selection.getRangeAt(0);
// will give you top, left, width, height
console.log(range.getBoundingClientRect());
I'm not sure about browser compatibility but I've found it works in the latest Chrome, Firefox and even IE7 (I think I tested 7, otherwise it was 9).
You can even do 'crazy' things like this: if you're typing "#hash" and the cursor is at the last h, you can look in the current range for the # character, move the range back by n characters and get the bounding-rect of that range, this will make the popup-div seem to 'stick' to the word.
One minor drawback is that contenteditable can be a bit buggy sometimes. The cursor likes to go to impossible places and you now have to deal with HTML input. But I'm sure browser vendors will address these problems are more sites starting using them.
Another tip I can give is: look at the rangy library. It attempts to be a fully featured cross-compatible range library. You don't need it, but if you're dealing with old browsers it might be worth you while.
maybe this will please you , it will tell the position of selection and the positition of the cursor so try to check the timer to get automatic position or uncheck to get position by clicking on Get Selection button
<form>
<p>
<input type="button" onclick="evalOnce();" value="Get Selection">
timer:
<input id="eval_switch" type="checkbox" onclick="evalSwitchClicked(this)">
<input id="eval_time" type="text" value="200" size="6">
ms
</p>
<textarea id="code" cols="50" rows="20">01234567890123456789012345678901234567890123456789 01234567890123456789012345678901234567890123456789 01234567890123456789012345678901234567890123456789 01234567890123456789012345678901234567890123456789 01234567890123456789012345678901234567890123456789 Sample text area. Please select above text. </textarea>
<textarea id="out" cols="50" rows="20"></textarea>
</form>
<div id="test"></div>
<script>
function Selection(textareaElement) {
this.element = textareaElement;
}
Selection.prototype.create = function() {
if (document.selection != null && this.element.selectionStart == null) {
return this._ieGetSelection();
} else {
return this._mozillaGetSelection();
}
}
Selection.prototype._mozillaGetSelection = function() {
return {
start: this.element.selectionStart,
end: this.element.selectionEnd
};
}
Selection.prototype._ieGetSelection = function() {
this.element.focus();
var range = document.selection.createRange();
var bookmark = range.getBookmark();
var contents = this.element.value;
var originalContents = contents;
var marker = this._createSelectionMarker();
while(contents.indexOf(marker) != -1) {
marker = this._createSelectionMarker();
}
var parent = range.parentElement();
if (parent == null || parent.type != "textarea") {
return { start: 0, end: 0 };
}
range.text = marker + range.text + marker;
contents = this.element.value;
var result = {};
result.start = contents.indexOf(marker);
contents = contents.replace(marker, "");
result.end = contents.indexOf(marker);
this.element.value = originalContents;
range.moveToBookmark(bookmark);
range.select();
return result;
}
Selection.prototype._createSelectionMarker = function() {
return "##SELECTION_MARKER_" + Math.random() + "##";
}
var timer;
var buffer = "";
function evalSwitchClicked(e) {
if (e.checked) {
evalStart();
} else {
evalStop();
}
}
function evalStart() {
var o = document.getElementById("eval_time");
timer = setTimeout(timerHandler, o.value);
}
function evalStop() {
clearTimeout(timer);
}
function timerHandler() {
clearTimeout(timer);
var sw = document.getElementById("eval_switch");
if (sw.checked) {
evalOnce();
evalStart();
}
}
function evalOnce() {
try {
var selection = new Selection(document.getElementById("code"));
var s = selection.create();
var result = s.start + ":" + s.end;
buffer += result;
flush();
} catch (ex) {
buffer = ex;
flush();
}
}
function getCode() {
// var s.create()
// return document.getElementById("code").value;
}
function clear() {
var out = document.getElementById("out");
out.value = "";
}
function print(str) {
buffer += str + "\n";
}
function flush() {
var out = document.getElementById("out");
out.value = buffer;
buffer = "";
}
</script>
look the demo here : jsbin.com
There is description of one hack for caret offset: Textarea X/Y caret coordinates - jQuery plugin
Also it will be better to use div element with contenteditable attribute if you can use html5 features.
How about appending a span element to the cloning div and setting the fake cursor based on this span's offsets? I have updated your fiddle here. Also here's the JS bit only
// http://stackoverflow.com/questions/263743/how-to-get-caret-position-in-textarea
var map = [];
var pan = '<span>|</span>'
//found @ http://davidwalsh.name/detect-scrollbar-width
function getScrollbarWidth() {
var scrollDiv = document.createElement("div");
scrollDiv.className = "scrollbar-measure";
document.body.appendChild(scrollDiv);
// Get the scrollbar width
var scrollbarWidth = scrollDiv.offsetWidth - scrollDiv.clientWidth;
// Delete the DIV
document.body.removeChild(scrollDiv);
return scrollbarWidth;
}
function getCaret(el) {
if (el.selectionStart) {
return el.selectionStart;
} else if (document.selection) {
el.focus();
var r = document.selection.createRange();
if (r == null) {
return 0;
}
var re = el.createTextRange(),
rc = re.duplicate();
re.moveToBookmark(r.getBookmark());
rc.setEndPoint('EndToStart', re);
return rc.text.length;
}
return 0;
}
$(function() {
var span = $('#pos span');
var textarea = $('textarea');
var note = $('#note');
css = getComputedStyle(document.getElementById('textarea'));
try {
for (i in css) note.css(css[i]) && (css[i] != 'width' && css[i] != 'height') && note.css(css[i], css.getPropertyValue(css[i]));
} catch (e) {}
note.css('max-width', '300px');
document.getElementById('note').style.visibility = 'hidden';
var height = note.height();
var fakeCursor, hidePrompt;
textarea.on('keyup click', function(e) {
if (document.getElementById('textarea').scrollHeight > 100) {
note.css('max-width', 300 - getScrollbarWidth());
}
var pos = getCaret(textarea[0]);
note.text(textarea.val().substring(0, pos));
$(pan).appendTo(note);
span.text(pos);
if (hidePrompt) {
hidePrompt.remove();
}
if (fakeCursor) {
fakeCursor.remove();
}
fakeCursor = $("<div style='width:5px;height:30px;background-color: #777;position: absolute;z-index:10000'> </div>");
fakeCursor.css('opacity', 0.5);
fakeCursor.css('left', $('#note span').offset().left + 'px');
fakeCursor.css('top', textarea.offset().top + note.height() - (30 + textarea.scrollTop()) + 'px');
hidePrompt = fakeCursor.clone();
hidePrompt.css({
'width': '2px',
'background-color': 'white',
'z-index': '1000',
'opacity': '1'
});
hidePrompt.appendTo(textarea.parent());
fakeCursor.appendTo(textarea.parent());
return true;
});
});
UPDATE: I can see that there's an error if the first line contains no hard line-breaks but if it does it seems to work well.
