How to align text so it renders the same for pdf and png (using fig.dpi_scale_trans)

This is a continuation of the question am having in Legend text alignment renders differently for pdf and png · Issue #15497 · matplotlib/matplotlib · GitHub. With png output, the code example below properly right aligns legend text, but when you change to pdf output it doesn’t work properly. It has to do with pixel unit movement which isn’t appropriate for pdf if your png dpi is different from 100, but I was told to use fig.dpi_scale_trans but I don’t know how?

text_widths = [text.get_window_extent(fig.canvas.get_renderer()).width
               for text in legend.get_texts()]
max_width = max(text_widths)
shifts = [max_width - w for w in text_widths]
for i, text in enumerate(legend.get_texts()):