cached images in knitr

[chriddyp]

In this PR in the Python-API (plotly/plotly.py#183) I'm displaying and caching an image as the iframe loads. Our new embed code similarly displays an image as the iframe waits to load.

We should probably explore one of those two solutions for the kintr pubs

[cpsievert]

Hey @chriddyp, does 095c814 fix this problem?

[chriddyp]

It doesn't. On plot.ly we created a new HTML embed code that looks e.g. like this:

<div>
    <a href="https://plot.ly/~chris/1638/" target="_blank" title="      " style="display: block; text-align: center;"><img src="https://plot.ly/~chris/1638.png" alt="      " style="max-width: 100%;width: 1305px;"  width="1305" onerror="this.onerror=null;this.src='https://plot.ly/404.png';" /></a>
    <script data-plotly="chris:1638"  src="https://plot.ly/embed.js" async></script>
</div>

(you can view the embed code at the ".html" endpoint of any graph, e.g. https://plot.ly/~chris/1638.html)

It loads a file called embed.js which replaces the image with an iframe if and once it loads. A couple advantages:

• Readers at least see an image while the graph is loading
• Mobile responsiveness is better, because we swap out the iframe with an image at small widths

Unfortunately, this embed code didn't work inside Python notebooks, but it might work in knitr