Center-align legend title and legend keys in ggplot2 for long legend titles

Question

I am having a hard time making the title of a legend center-aligned relative to the legend keys when the legend title is long. There is a question from a year ago that works

Answer 1

you'd have to change the source code. Currently it computes the widths for the title grob and the bar+labels, and left-justifies the bar+labels in the viewport (gtable). This is hard-coded.