I'm currently rendering text with FreeType + Harfbuzz and am now trying to introduce vertical text rendering (mainly for east asian scripts).
The issue I'm facing is that I can't figure out how wide a column of text should be. For horizontal text we can find out the line height with ascent - descent, but since these values are not provided in the case of vertical text ('ascent' / 'descent' is simple the left and right part of the glyph respectively) I have no idea how wide my text columns should be.
I tried using bbox width for the font, but the box changes drastically between different fonts, giving no good info.
