Canvas still sucks for rendering fonts. Getting accurate font metrics is still hacky[1] and more advanced methods are still experimental[2]. Though I'm sure with Google Docs moving to canvas, some of this will be expedited. But it's yet another one of those things about web tech that anyone would half a brain would tell you should have been there day one.

[1] https://stackoverflow.com/questions/1134586/how-can-you-find...

[2] https://developer.mozilla.org/en-US/docs/Web/API/TextMetrics