YUI Library Examples: StyleSheet: Adjusting a page theme on the fly

<!-- The original body content is above -->
<div id="form_container">
    <form class="yui3-widget-bd" id="theme_form" action="#" method="get">
        <fieldset>
            <h3>Update Theme</h3>
            <label for="font_size">Font size:</label>
            <input type="text" size="3" id="font_size" value="16px">
 
            <label for="heading_color">Heading color:</label>
            <input type="text" size="12" id="heading_color" value="#005A9C">
 
            <label for="link_hover">Link hover backgound:</label>
            <input type="text" size="12" id="link_hover" value="#ffa">
        </fieldset>
        <input type="submit">
    </form>
</div>

// Create a new YUI instance, requiring stylesheet, overlay, slider, and the
// dd-plugin to make the overlay draggable
YUI().use("stylesheet", "overlay", "slider", "dd-plugin", function (Y) {
 
    var myStyleSheet = new Y.StyleSheet(),
        overlayContent = Y.one('#form_container'),
        overlay,
        slider,
        slider_container,
        fontSizeInput,
 
    // Create the Overlay, using the form container as the contentBox.
    // The form is assigned a class yui-widget-bd that will be automatically
    // discovered by Overlay to populate the Overlay's body section.
    // The overlay is positioned in the top right corner, but made draggable
    // using Y.Plugin.Drag, provided by the dd-plugin module.
    overlay = new Y.Overlay({
        srcNode: overlayContent,
        width: '225px',
        align: { points: [ Y.WidgetPositionAlign.TR, Y.WidgetPositionAlign.TR ] },
        plugins: [ Y.Plugin.Drag ]
    }).render();
 
    // Slider needs a parent element to have the sam skin class for UI skinning
    overlayContent.addClass('yui3-skin-sam');
 
    // Progressively enhance the font-size input with a Slider
    fontSizeInput = Y.one('#font_size');
    fontSizeInput.set('type','hidden');
    fontSizeInput.get('parentNode').insertBefore(
        Y.Node.create('6 <span></span> 36'),
        fontSizeInput);
 
    slider_container = fontSizeInput.previous( "span" );
 
    // Create a Slider to contain font size between 6px and 36px, using the
    // page's current font size as the initial value.
    // Set up an event subscriber during construction to update the replaced
    // input field's value and apply the change to the StyleSheet
    slider = new Y.Slider({
        length: '100px',
        min: 6,
        max: 36,
        value: parseInt(Y.one('body').getStyle('fontSize')) || 13,
        after: {
            valueChange: function (e) {
                var size = e.newVal + 'px';
 
                this.thumb.set('title', size);
                fontSizeInput.set('value', size);
 
                myStyleSheet.set('body', { fontSize: size });
            }
        }
    }).render( slider_container );
 
    // The color inputs are assigned keyup listeners that will update the
    // StyleSheet if the current input value is a valid CSS color value
 
    // The heading input affects all h1s, h2, and h3s
    Y.on('keyup', function (e) {
        var color = this.get('value');
 
        if (isValidColor(color)) {
            myStyleSheet.set('h1, h2, h3', { color: color });
        }
    }, '#heading_color');
 
    // The link hover affects the background color of links when they are
    // hovered.  There is no way other than via stylesheet modification to
    // change pseudo-class styles.
    Y.on('keyup', function (e) {
        var color = this.get('value');
 
        if (isValidColor(color)) {
            myStyleSheet.set('a:hover', { backgroundColor: color });
        }
    }, '#link_hover');
 
    // Progressive form enhancement complete, now prevent the form from
    // submitting normally.
    Y.on('submit', function (e) {
        e.halt();
    }, '#theme_form');
 
	// A rudimentary validator to make sure we're not trying to set
	// invalid color values in StyleSheet.
	function isValidColor(v) {
        return /^#[0-9a-f]{3}(?:[0-9a-f]{3})?$/i.test(v) ||
               /^rgb\(\s*\d+\s*,\s*\d+\s*,\s*\d+\s*\)$/.test(v) ||
               /^[a-z]{3,}$/i.test(v);
	}
 
});

/* For supporting browsers, the overlay is rendered semi-transparent with
 * fancy rounded corners */
.yui3-overlay {
    background: rgba(128,128,128,0.3);
    -moz-border-radius: 10px;
    -webkit-border-radius: 10px;
    border-radius: 10px;
    padding: 7px;
    cursor: move;
}
 
.yui3-overlay-content {
    background: rgba(205,205,205,0.3);
    -moz-border-radius: 10px;
    -webkit-border-radius: 10px;
    border-radius: 10px;
    padding: 1px;
} 
 
.yui3-overlay form {
    background: #f2fbff url(gradient-promo.png) repeat-x scroll 0 0;
    border: 2px solid #fff;
    -moz-border-radius: 10px;
    -webkit-border-radius: 10px;
    border-radius: 10px;
    margin: 0;
    padding: 0;
    font-size: 13px;
}
 
.yui3-overlay fieldset {
    border: 1px solid #bcd;
    -moz-border-radius: 10px;
    -webkit-border-radius: 10px;
    border-radius: 10px;
    margin: 0;
    padding: 20px;
}
 
.yui3-overlay h3 {
    border-bottom: 2px solid #fff;
    color: #479;
    background: transparent;
    margin: 0;
    font-size: 175%;
}
 
.yui3-overlay label {
    display: block;
    margin: 1.3em 0 0.5ex;
    font-weight: bold;
    color: #003;
}
 
.yui3-overlay p {
    margin: 2em 0 0;
}
 
/* override the move cursor for the Slider */
.yui3-overlay .yui3-slider:hover {
    cursor: default;
}