I need the coordinates in pixels of the beginning of the text selection (anywhere on the page, not in a textarea).
I tried using the cursor coordinates but this didn't work quite well because the cursor coordinates and the beginning of the selection are not always the same (for example when a user drags over a text).
I hope someone has the solution!
In IE >= 9 and non-IE browsers (Firefox 4+, WebKit browsers released since early 2009, Opera 11, maybe earlier), you can use the getClientRects() method of Range. In IE 4 - 10, you can use the boundingLeft and boundingTop properties of the TextRange that can be extracted from the selection. Here's a function that will do what you want in recent browsers.
Note that there are some situations in which you may wrongly get co-ordinates 0, 0, as mentioned in the comments by @Louis. In that case you'll have to fall back to a workaround of temporarily inserting an element and getting its position.
jsFiddle: http://jsfiddle.net/NFJ9r/132/
Code:
function getSelectionCoords(win) {
win = win || window;
var doc = win.document;
var sel = doc.selection, range, rects, rect;
var x = 0, y = 0;
if (sel) {
if (sel.type != "Control") {
range = sel.createRange();
range.collapse(true);
x = range.boundingLeft;
y = range.boundingTop;
}
} else if (win.getSelection) {
sel = win.getSelection();
if (sel.rangeCount) {
range = sel.getRangeAt(0).cloneRange();
if (range.getClientRects) {
range.collapse(true);
rects = range.getClientRects();
if (rects.length > 0) {
rect = rects[0];
}
x = rect.left;
y = rect.top;
}
// Fall back to inserting a temporary element
if (x == 0 && y == 0) {
var span = doc.createElement("span");
if (span.getClientRects) {
// Ensure span has dimensions and position by
// adding a zero-width space character
span.appendChild( doc.createTextNode("\u200b") );
range.insertNode(span);
rect = span.getClientRects()[0];
x = rect.left;
y = rect.top;
var spanParent = span.parentNode;
spanParent.removeChild(span);
// Glue any broken text nodes back together
spanParent.normalize();
}
}
}
}
return { x: x, y: y };
}
UPDATE
I submitted a WebKit bug as a result of the comments, and it's now been fixed.