Created attachment 286836 [details]
The attached testcase was provided by Jacques Distler (from https://golem.ph.utexas.edu/wiki/instiki/show/Sandbox).
When you zoom in / out, the slash and 'D' elements are no longer displayed correctly. This is probably because we store two members m_ascent & m_contentRect on the renderer class and thy are not updated when zooming in / out. In general, in the past the solution for this kind of problem has been to get rid of these members. That's at least easy for m_ascent.
@Jacques: Do you still have the issue? I can't reproduce it with the testcase on WebKitBuild nightly or epiphany release.
Seems to work fine now (Safari 11.0.1 (12604.3.5.1.1), MacOSX).
And it does not seem to be an issue in iOS 11.1.2 either.
Thanks. I'm not sure what resolved this. Maybe bug 161127 helped but it was probably not enough. Also, there was bug 160077 where I worked on that Dirac equation too but I don't remember exactly. Let's marked it as fixed.