source: trunk/workshop-routing-foss4g/web/GeoExt/docs/_sources/lib/GeoExt/widgets/LayerOpacitySlider.txt @ 76

.. currentmodule:: GeoExt

:class:`GeoExt.LayerOpacitySlider`
================================================================================


.. cssclass:: meta


Extends
    * `Ext.Slider <http://dev.sencha.com/deploy/dev/docs/?class=Ext.Slider>`_
    



xtype
    ``gx_opacityslider``




.. class:: LayerOpacitySlider(config)

    Create a slider for controlling a layer's opacity.



Example Use
-----------

Sample code to render a slider outside the map viewport:

.. code-block:: javascript

    var slider = new GeoExt.LayerOpacitySlider({
        renderTo: document.body,
        width: 200,
        layer: layer
    });

Sample code to add a slider to a map panel:

.. code-block:: javascript

    var layer = new OpenLayers.Layer.WMS(
        "Global Imagery",
        "http://maps.opengeo.org/geowebcache/service/wms",
        {layers: "bluemarble"}
    );
    var panel = new GeoExt.MapPanel({
        renderTo: document.body,
        height: 300,
        width: 400,
        map: {
            controls: [new OpenLayers.Control.Navigation()]
        },
        layers: [layer],
        extent: [-5, 35, 15, 55],
        items: [{
            xtype: "gx_opacityslider",
            layer: layer,
            aggressive: true,
            vertical: true,
            height: 100,
            x: 10,
            y: 20
        }]
    });

    


Config Options
--------------

Configuration properties in addition to
those listed for `Ext.Slider <http://dev.sencha.com/deploy/dev/docs/?class=Ext.Slider>`_.


.. describe:: aggressive

    ``Boolean``
    If set to true, the opacity is changed as soon as the thumb is moved.
    Otherwise when the thumb is released (default).

.. describe:: changeVisibility

    ``Boolean``
    If set to true, the layer's visibility is handled by the
    slider, the slider makes the layer invisible when its
    value is changed to the min value, and makes the layer
    visible again when its value goes from the min value
    to some other value. The layer passed to the constructor
    must be visible, as its visibility is fully handled by
    the slider. Defaults to false.

.. describe:: changeVisibilityDelay

    ``Number`` Time in milliseconds before changing the layer's visibility.
    If the value changes again within that time, the layer's visibility
    change does not occur. Only applicable if changeVisibility is true.
    Defaults to 5.

.. describe:: complementaryLayer

    ``OpenLayers.Layer`` or :class:`GeoExt.data.LayerRecord`
    If provided, a layer that will be made invisible (its visibility is
    set to false) when the slider value is set to its max value. If this
    slider is used to fade visibility between to layers, setting
    ``complementaryLayer`` and ``changeVisibility`` will make sure that
    only visible tiles are loaded when the slider is set to its min or max
    value. (optional)

.. describe:: delay

    ``Number`` Time in milliseconds before setting the opacity value to the
    layer. If the value change again within that time, the original value
    is not set. Only applicable if aggressive is true.

.. describe:: inverse

    ``Boolean``
    If true, we will work with transparency instead of with opacity.
    Defaults to false.

.. describe:: layer

    ``OpenLayers.Layer`` or :class:`GeoExt.data.LayerRecord`
    The layer this slider changes the opacity of. (required)

.. describe:: value

    ``Number``
    The value to initialize the slider with. This value is
    taken into account only if the layer's opacity is null.
    If the layer's opacity is null and this value is not
    defined in the config object then the slider initializes
    it to the max value.






Public Methods
--------------

Public methods in addition to those
listed for `Ext.Slider <http://dev.sencha.com/deploy/dev/docs/?class=Ext.Slider>`_.


.. method:: LayerOpacitySlider.setLayer

    :param layer: ``OpenLayers.Layer`` or :class:`GeoExt.data.LayerRecord`
    
    Bind a new layer to the opacity slider.