Xaringan: Handle remark macros via xaringan?

[gavinsimpson]

From version 0.8.0, remark.js has had the ability to take user defined macros that can control output. I cam across this because I wanted to control the size of a single image without polluting my MD with raw HTML.

I found this solution https://github.com/gnab/remark/issues/72#issuecomment-62225566 which suggests the following

![:scale 50%](image.jpg)

with this macro

remark.macros.scale = function (percentage) {
  var url = this;
  return '<img src="' + url + '" style="width: ' + percentage + '" />';
};

The macro needs to be inserted right before

var slideshow = remark.create();

Are there any plans to allow this advanced usage of remark.js within xaringan?

(I know I can scale the image using HTML or CSS; this Q is more about handling macros which are a feature of the underlying library.)

[yihui]

Thanks for letting me know this hidden feature! Not being able to scale images using the Markdown syntax is probably the only reason that I was not totally satisfied with remark.js.

I'll think more about how to support macros.

[pat-s]

That would be a great enhancement :+1:

[gavinsimpson]

Thanks @yihui. I was wondering if the concept of includes from rmarkdown would be a good way to approach this?

A user would put the javascript macros they want in my_macros.js and then they can add

includes:
  - macro: 'my_macros.js'

in the YAML header and then have xaringan insert the content of my_macros.js into the rendered file in the appropriate location?

[yihui]

The includes option is not extensible. I just added an option beforeInit in the nature list of moon_reader(). See https://slides.yihui.name/xaringan/#30