gistfile1.xml

{namespace flux=FluidTYPO3\Flux\ViewHelpers}
<f:layout name="Content" />

<f:section name="Configuration">
    <flux:form id="frame" label="Frame" icon="Icons/Page.gif">
        <!-- Insert fields, sheets, grid, form section objects etc. here, in this flux:flexform tag -->
        <flux:grid>
            <flux:grid.row>
                <flux:grid.column>
                    <flux:form.content name="main" label="Inhalt"/>
                </flux:grid.column>
            </flux:grid.row>
        </flux:grid>
        <flux:field.checkbox name="mobile"  label="Mobile anzeigen" default="1"/>
        <flux:field.checkbox name="tablet"  label="Tablet anzeigen" default="1"/>
        <flux:field.checkbox name="desktop" label="Desktop anzeigen" default="1"/>
    </flux:form>
</f:section>

<f:section name="Preview">
    <flux:widget.grid />
    <link href="//netdna.bootstrapcdn.com/font-awesome/4.1.0/css/font-awesome.min.css" rel="stylesheet">
     <span class="fa-stack fa-lg">
        <i class="fa fa-mobile fa-stack-1x"></i>
            <f:if condition="{mobile}">
                <f:then></f:then>
                <f:else>
                    <i class="fa fa-ban fa-stack-2x text-danger"></i>
                </f:else>
            </f:if>
    </span>

        <span class="fa-stack fa-lg">
        <i class="fa fa-tablet fa-stack-1x"></i>
            <f:if condition="{tablet}">
                <f:then></f:then>
                <f:else>
                    <i class="fa fa-ban fa-stack-2x text-danger"></i>
                </f:else>
            </f:if>
    </span>

        <span class="fa-stack fa-lg">
        <i class="fa fa-desktop fa-stack-1x"></i>
            <f:if condition="{desktop}">
                <f:then></f:then>
                <f:else>
                    <i class="fa fa-ban fa-stack-2x text-danger"></i>
                </f:else>
            </f:if>
    </span>
</f:section>

<f:section name="Main">
    <div class="frame selective-show mobile-{mobile} tablet-{tablet} desktop-{desktop}">
        <flux:content.render area="main"/>
    </div>
</f:section>