These types of text metrics bugs show up in my code over and over and over and over again. I keep making them! When I was working on the icon view in Finder, icon layout, multi-line icon labels, additional info text and anything else using metrics would constantly be in danger of collapsing. Was this because I was a sloppy coder? Maybe... but the whole stack is so finicky and brittle and filled with some many special cases and different ways of getting layout measured it takes a lot of work to get all of the edge cases covered.

It isn't just Apple of course. I encountered almost the exact same bugs working on Nautilus at Eazel and various projects at Be. And in PowerPlant, and the Think Class Library and MacApp and... the list goes on.

My current music notation project pushed me to try and make multiple font support and layout as robust as possible, but I keep getting burnt! Text layout and metrics is just a difficult area.