How to dynamically wrap facet label using ggplot2

Question

I\'m looking for a way to dynamically wrap the strip label text in a facet_wrap or facet_grid call. I\'ve found a way to accomplish this using

Answer 1

(too long as a comment, but not a real answer either)

I don't think a general solution will exist directly within ggplot2; it's the classic problem of self-reference for grid units: ggplot2 wants to calculate the viewport sizes on-the-fly, while the strwrap would need to know a firm width to decide how to split the text. (there was a very similar question, but I forget when and where).

You could however write a helping function to estimate how much wrapping you'll need before plotting. In pseudo code,

# takes the facetting variable and device size
estimate_wrap = function(f, size=8, fudge=1){ 

    n = nlevels(f)
    for (loop over the labels of strwidth wider than (full.size * fudge) / n){
     new_factor_level[ii] = strwrap(label[ii], available width)
    }

  return(new_factor)
}

(with some standard unit conversions required)

Of course, things would get more complicated if you wanted to use space="free".