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# YUI Library Examples: Slider Control: Bottom to top Vertical Slider

# Slider Control: Bottom to top Vertical Slider

This example demonstrates a vertical implementation of the YUI Slider Control. Some characteristics of this implementation include the following:

- The slider range is 200 pixels.
- CSS is used to place the slide thumb at the bottom of the slider.
- Custom logic is added to the slider instance to convert the offset value to a "real" value calculated from a provided min/max range.
- The custom min value is set to 10; the max 110.
- Once the slider has focus, the up and down keys will move the thumb 20 pixels (changing the "real" value by 10).
- When the slider value changes, the pixel offset and calculated value are reported below the slider.

View example in new window.

Pixel offset from start: 0

Calculated Value: 0

## Building a Bottom-Up Vertical Slider

You supply your own markup for the slider. Keep in mind the following points about markup for YUI Slider Control implementations:

- The thumb element should be a child of the slider background
- The tabindex attribute lets this element receive focus in most browsers.
- If the slider background can receive focus, the arrow keys can be used to change this slider's value.
- We use an `<img>` element rather than a CSS background for the thumb to get around a performance bottleneck when animating the thumb's position in IE.
- Both elements should have an explicit CSS position: `relative` or `absolute`.
- Don't apply a CSS border to the slider background

CSS:

#slide_bg { position: relative; background: url(assets/bg-v.gif) 12px 0 no-repeat; height: 228px; width: 48px; } #slide_thumb { cursor: default; position: absolute; top: 200px; /* To initialize the slide thumb at the bottom */ }

Markup:

<div id="demo"> <div id="slide_bg" tabindex="-1"> <div id="slide_thumb"><img src="assets/thumb-bar.gif"></div> </div> <p>Pixel offset from start: <span id="d_offset"></span></p> <p>Calculated Value: <span id="d_val"></span></p> </div>

## Invert the `getValue` offset

Offset values returned by the `getValue()` methods, or passed as a parameter to the `change` event callback, increase as the slider moves left-to-right and top-to-bottom. Making the value increase in the opposite direction is as simple as multiplying by -1.

Look for the magic in this code:

YAHOO.util.Event.onDOMReady(function () { // the slider can move up 200 pixels var upLimit = 200; // and down 0 pixels var downLimit = 0; // Create the Slider instance var slider = YAHOO.widget.Slider.getVertSlider( 'slide_bg', 'slide_thumb', upLimit, downLimit); // Add a little functionality to the instance YAHOO.lang.augmentObject(slider, { // A custom value range for the slider minValue : 10, maxValue : 110, // A method to retrieve the calculated value, per the value range getCalculatedValue : function () { // HERE'S THE MAGIC // invert the offset value so "real" values increase as the // slider moves up var offset = -1 * this.getValue(); // Convert the offset to a value in our configured range var conversionFactor = (this.maxValue - this.minValue) / (this.thumb.topConstraint + this.thumb.bottomConstraint); return Math.round(offset * conversionFactor) + this.minValue; } }); // display the native offset and the calculated while sliding var offset_span = YAHOO.util.Dom.get('d_offset'); var calc_span = YAHOO.util.Dom.get('d_val'); slider.subscribe('change', function (offsetFromStart) { offset_span.innerHTML = offsetFromStart; calc_span.innerHTML = this.getCalculatedValue(); }); });

For horizontal Sliders, multiplying the offset by -1 makes values increase right-to-left.

## Configuration for This Example

You can load the necessary JavaScript and CSS for this example from Yahoo's servers. Click here to load the YUI Dependency Configurator with all of this example's dependencies preconfigured.

### YUI Logger Output:

Note: Logging and debugging is currently turned off for this example.

Reload with logging
and debugging enabled.

### Slider Control Examples:

- Basic Vertical Slider
- Horizontal Slider with Tick Marks
- RBG Slider Control
- Bottom to top Vertical Slider
- Horizontal Slider with two thumbs
- Dual-thumb Slider with range highlight
- Basic Features (included with examples for ProgressBar Control)
- Events (included with examples for ProgressBar Control)
- Slider Button (included with examples for Button Control)
- Complex Application (included with examples for Layout Manager)

### More Slider Control Resources:

- User's Guide (external)
- API Documentation
- Cheat Sheet PDF (external)

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