[Interest] Enabling Harfbuzz on Mac

[Joshua Grauman]

Hello all,

According to this page, it is now possible to enable Harfbuzz on Mac by setting 
an environment variable:
https://bugreports.qt-project.org/browse/QTBUG-17728

However, unless I'm missing something I haven't been able to enable 
Harfbuzz on Mac. I'm using Qt 4.8, which according to the sources should 
have this feature enabled. It should be as simple as setting the 
environment variable: QT_ENABLE_HARFBUZZ which I have done. However, after 
doing this, my text output still looks drastically different on Mac than 
on Windows/Linux. I am using a TTF font by the way. Am I correct that if I 
am using Harfbuzz on Mac my text should be pixel perfect with 
Windows/Linux (with maybe the exception of subpixel aliasing). My outputs 
are drastically different. The text sizes are many pixels different, even 
with the same font and same font size. Most importantly, there are still 
some rendering bugs on Mac which aren't on Windows/Linux which leads me to 
believe I haven't enabled Harfbuzz properly. I used the following code 
which is pulled straight from the Qt sources and the environment variable 
seems set properly: QByteArray v = qgetenv("QT_ENABLE_HARFBUZZ"); So does 
anyone have any ideas on what I am missing? Why would the text output 
still be different on Mac?

Josh