Passing fig.width into a taglist

Question

The rgl widget responds to the figure width and height specified in knitr code chunk options, e.g.

```{r fig.width=2, fig.height=2}
library(rgl); example(plot3d);
rglwidget()
```

gives a small plot (192 x 192 on my screen). However, if I put rglwidget() in a browsable tagList, it doesn't:

```{r fig.width=2, fig.height=2}
library(rgl); example(plot3d)
library(htmltools)
browsable(tagList(rglwidget(), rglwidget()))
```

This gives two full size widgets. Debugging the Javascript shows that each is being initialized as 960 by 500, not 192 by 192 as in the first example.

Is there a way to say that I want the width and height values to be passed into the widgets in the tagList?

P.S. This has nothing to do with rgl; leaflet has the same problem in

```{r fig.width=2, fig.height=2}
library(leaflet); library(htmltools)
browsable(tagList(leaflet() %>% addTiles())
```

user2554330 user2554330 · Accepted Answer · 2017-03-03T12:01:01

Since code in a chunk can read the options for the chunk, probably the best solution here is to write small functions that obtain the size of the figure in pixels, and use those in explicit settings in the widget.

For example,

```{r fig.width=2, fig.height=2}
library(leaflet); library(htmltools)

# This one is too big:
browsable(tagList(leaflet() %>% addTiles()))

# Get the current figure size in pixels:
w <- function() 
  with(knitr::opts_current$get(c("fig.width", "dpi", "fig.retina")),
       fig.width*dpi/fig.retina)
h <- function() 
  with(knitr::opts_current$get(c("fig.height", "dpi", "fig.retina")),
       fig.height*dpi/fig.retina)

# This is what I wanted:
browsable(tagList(leaflet(width = w(), height = h()) %>% addTiles()))
```

Passing fig.width into a taglist

1 Answers