The FontLoader detects and notifies when specified font-families loaded and rendered by the browser.
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README.md

FontLoader

The FontLoader detects and notifies when fonts of the specified font-families loaded and rendered by the browser. This, without using timeouts (when possible) to poll for element dimensions like it is done traditionally. Instead it utilizes the "scroll" event to receive an instantaneous event when element size is changed. In IE10 and lower it uses "onresize" event which brings a similar result. In addition it utilizes AdobeBlank font to eliminate known issues related to metric compatible fonts.

More info on how the FontLoader works can be found here.

Usage

The FontLoader receives an array of fonts and notifies the delegate object via fontLoaded and complete methods when specific or all fonts were loaded respectively. The FontLoader does not load the fonts, the insertion of specified font-families into the document should be done elsewhere.

The FontLoader(fonts, delegate, timeout) constructor receives three parameters:

  1. font - array of font-family strings with optionally specified variations using FVD notation, or FontDescriptor objects.
  2. delegate - the delegate object with following optional methods which are invoked in the context of the delegate object:
  • fontLoaded(font) - called when one of the specified fonts was loaded with the font itself passed as the FontDescriptor object.
  • complete(error) - called when all specified fonts were loaded, in which case the error will be null. Or when the timeout was reached before all specified fonts were loaded, in which case error will be an object with two fields - the message string and the notLoadedFonts array with all the fonts that weren't loaded as FontDescriptor objects.
  1. timeout - optional timeout in milliseconds, default is 3000. Pass null to disable the timeout.

After the FontLoaded was instantiated, call loadFonts method to begin watching for fonts to load. If some or all fonts were already loaded, the appropriate delegate methods will be invoked as expected.

The FontDescriptor object is an object with the following fields:

  1. family - the font family (e.g.: 'Open Sans')
  2. weight - the font weight (e.g.: 400)
  3. style - the font style (e.g.: 'italic')
  4. stretch - the font stretch (e.g.: 'condensed'), optional

Example

<!DOCTYPE html>
<html>
<head>
    <style type="text/css">
        @font-face {
            font-family: 'MyFont';
            font-style: normal;
            font-weight: 400;
            src:  url(path/to/MyFont.woff) format('woff');
        }
        @font-face {
            font-family: 'MyOtherFont';
            font-style: italic;
            font-weight: 800;
            src:  url(path/to/MyOtherFont.woff) format('woff');
        }
    </style>
</head>
<body>
    <script type="text/javascript" src="FontLoader.js"></script>
    <script type="text/javascript">
        var fontLoader = new FontLoader(["MyFont", "MyOtherFont:i8"], {
            "fontLoaded": function(font) {
                // One of the fonts was loaded
                console.log("font loaded: " + font.family);
            },
            "complete": function(error) {
                if (error !== null) {
                    // Reached the timeout but not all fonts were loaded
                    console.log(error.message);
                    console.log(error.notLoadedFonts);
                } else {
                    // All fonts were loaded
                    console.log("all fonts were loaded");
                }
            }
        }, 3000);
        fontLoader.loadFonts();
    </script>
</body>
</html>