documentation: values list for legend.box.just appears incomplete

[twest820]

The current documentation for theme() states

legend.box.just justification of each legend within the overall bounding box, when there are multiple legends ("top", "bottom", "left", or "right")

I happened to need theme(legend.box.just = "center") so I tried it anyway and found it behaved as expected when centering two legends (an alpha legend and a merged color plus linetype legend) within a bottom legend box.

So life is good. But it would be useful to know if this just signals the documentation is a bit out of date or if I'm relying on a behavior that's formally unsupported.

Version; ggplot 3.3.2

[clauswilke]

The value of legend.box.just is converted into numerical justification parameters using the function grid::valid.just():

ggplot2/R/guides-.r

Line 277 in a11e098

just <- valid.just(theme$legend.box.just)

So you can set legend.box.just to whatever values valid.just() understands. Unfortunately that function isn't well documented either. The documentation literally says e.g., "left" becomes 0, "right" becomes 1, etc, ....

The value "center" is supported, though, and the theme documentation should say so.