javascript - Creating a collapsed range from a pixel position in FF/Webkit

Question

Using JavaScript, I would like to create a collapsed range from a pixel position, in order to insert new nodes in the flow of the document, after the range identified by this position.

This can be done with the TextRange object in Internet Exporer (moveToPoint(x, y) method).

How can I do this in FireFox & Webkit?

I can get the container element from the position with document.elementFromPoint(x, y). But when the position happens to be inside a text node, how do I get more information about the text offset required to build a range?

Answer 1

Here is my implementation of caretRangeFromPoint for old browsers:

if (!document.caretRangeFromPoint) {
    document.caretRangeFromPoint = function(x, y) {
        var log = "";

        function inRect(x, y, rect) {
            return x >= rect.left && x <= rect.right && y >= rect.top && y <= rect.bottom;
        }

        function inObject(x, y, object) {
            var rects = object.getClientRects();
            for (var i = rects.length; i--;)
                if (inRect(x, y, rects[i]))
                    return true;
            return false;
        }

        function getTextNodes(node, x, y) {
            if (!inObject(x, y, node))
                return [];

            var result = [];
            node = node.firstChild;
            while (node) {
                if (node.nodeType == 3)
                    result.push(node);
                if (node.nodeType == 1)
                    result = result.concat(getTextNodes(node, x, y));

                node = node.nextSibling;
            }

            return result;
        }

        var element = document.elementFromPoint(x, y);
        var nodes = getTextNodes(element, x, y);
        if (!nodes.length)
            return null;
        var node = nodes[0];

        var range = document.createRange();
        range.setStart(node, 0);
        range.setEnd(node, 1);

        for (var i = nodes.length; i--;) {
            var node = nodes[i],
                text = node.nodeValue;


            range = document.createRange();
            range.setStart(node, 0);
            range.setEnd(node, text.length);

            if (!inObject(x, y, range))
                continue;

            for (var j = text.length; j--;) {
                if (text.charCodeAt(j) <= 32)
                    continue;

                range = document.createRange();
                range.setStart(node, j);
                range.setEnd(node, j + 1);

                if (inObject(x, y, range)) {
                    range.setEnd(node, j);
                    return range;
                }
            }
        }

        return range;
    };
}