How to make scrollable slides in an ioslides presentation with rmarkdown
Self-answer:
The bit of CSS that will make the slide scrollable (both horizontally and vertically but you just have to remove one line if only vertical scrolling is needed) is:
slides > slide { overflow-x: auto !important; overflow-y: auto !important;}Note that the slide gets a height from ioslide so there is no need to specify a height (and in fact it seems to introduce visual glitches if you do). Using auto instead of scroll makes sure a scrollbar only appears when there is a need.
You can either add this CSS directly in the Rmd in between <style> tags or put the CSS in a separate file (e.g. scrollable_slides.css).
The CSS file can then be added to the Rmd like this (assuming scrollable_slides.css is in the same directory as the Rmd):
---title: "..."output: ioslides_presentation: css: 'scrollable_slides.css'runtime: shiny---