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?
Google is your friend: Floating Layer At Cursor Position http://www.willmaster.com/blog/css/floating-layer-at-cursor-position.php
Edit: Or this: http://www.webreference.com/programming/javascript/ncz/column2/
But I think I am missing some information. Is the problem that you cannot get the DIV to display over the textbox?
EDIT 2: Oops you want the cursor position in the textbox? Convoluted, but really GOOGLE IS YOUR FRIEND:
This blog post seems to address your question, but unfortunately the author admits he has only tested it in IE 6.
I posted a topic related to this problem in Russian JavaScript related 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 check them in original one.
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 create invisible DIV, copy all styles and content of the text box into that DIV, then insert HTML element at exactly the same position in text where the caret is in the text box and get coordinates of that element.
There is a specific implementation for BUEditor. http://ufku.com/drupal/bueditor/contributions/cursor-offset