takahe/templates/activities/_image_viewer.html

<script type="text/hyperscript">
    def imageviewer.show(source)
        set source_url to (<img /> in source) @data-original-url
        set source_alt to (<img /> in source) @alt
        set image to <#image-viewer img />
        set figcaption to <#image-viewer figcaption />

        -- fill information
        set image@src to source_url
        set image@alt to source_alt
        set figcaption's textContent to source_alt

        -- show image viewer
        show #image-viewer with display:flex
        transition #image-viewer's opacity from 0 to 1 over 300ms
        focus() on first <#image-viewer button />
    end
    def imageviewer.close()
        transition #image-viewer's opacity to 0 over 300ms
        hide #image-viewer
        set <#image-viewer img /> @src to ''
        set <#image-viewer img /> @alt to ''
        set <#image-viewer figcaption />'s textContent to ''
    end
</script>
<figure id="image-viewer" _="on click imageviewer.close()">
    <picture>
        <img src="" alt=""/>
    </picture>
    <figcaption></figcaption>
    <button aria-label="Close">
        <i class="fa fa-3x fa-times"></i>
    </button>
</figure>