MediaWiki:Common.js

/* Any JavaScript here will be loaded for all users on every page load. */
var tooltips = document.querySelectorAll('.tooltip span');

window.onmousemove = function (e) {
    var xoffset = (e.clientX + 20),
        yoffset = (e.clientY + 20);
    for (var i = 0; i < tooltips.length; i++) {
    	var x = xoffset, y = yoffset;
    	
    	var tooltip_rect = tooltips[i].getBoundingClientRect();
    	
    	if ((tooltip_rect.x + tooltip_rect.width) > window.innerWidth) // Out on the right
    		x = -tooltip_rect.width - 5;  // Simulate a "right: tipX" position
		if ((tooltip_rect.y + tooltip_rect.height) > window.innerHeight) // Out on the bottom
    		y = -tooltip_rect.height - 5    // Align on the top
    	
        tooltips[i].style.top = y + 'px';
        tooltips[i].style.left = x + 'px';
    }
};