Using jQuery to know when @font-face fonts are loaded?

Question

I am using @font-face and I hate that Firefox shows the default font, waits to load the @font-face font, then replaces it. So the whole page flashes with the new font.

Answer 1

I use this function - tested in Safari, Chrome, Firefox, Opera, IE7, IE8, IE9:

function waitForWebfonts(fonts, callback) {
    var loadedFonts = 0;
    for(var i = 0, l = fonts.length; i < l; ++i) {
        (function(font) {
            var node = document.createElement('span');
            // Characters that vary significantly among different fonts
            node.innerHTML = 'giItT1WQy@!-/#';
            // Visible - so we can measure it - but not on the screen
            node.style.position      = 'absolute';
            node.style.left          = '-10000px';
            node.style.top           = '-10000px';
            // Large font size makes even subtle changes obvious
            node.style.fontSize      = '300px';
            // Reset any font properties
            node.style.fontFamily    = 'sans-serif';
            node.style.fontVariant   = 'normal';
            node.style.fontStyle     = 'normal';
            node.style.fontWeight    = 'normal';
            node.style.letterSpacing = '0';
            document.body.appendChild(node);

            // Remember width with no applied web font
            var width = node.offsetWidth;

            node.style.fontFamily = font + ', sans-serif';

            var interval;
            function checkFont() {
                // Compare current width with original width
                if(node && node.offsetWidth != width) {
                    ++loadedFonts;
                    node.parentNode.removeChild(node);
                    node = null;
                }

                // If all fonts have been loaded
                if(loadedFonts >= fonts.length) {
                    if(interval) {
                        clearInterval(interval);
                    }
                    if(loadedFonts == fonts.length) {
                        callback();
                        return true;
                    }
                }
            };

            if(!checkFont()) {
                interval = setInterval(checkFont, 50);
            }
        })(fonts[i]);
    }
};

Use it like:

waitForWebfonts(['MyFont1', 'MyFont2'], function() {
    // Will be called as soon as ALL specified fonts are available
});