For those playing with Windows 7, check out some of the work Bas Schouten has been doing with adding DirectWrite support to Firefox. DirectWrite is Microsoft’s replacement for Uniscribe in Windows 7 and it has much better rendering of Postscript CFF fonts, fonts that are typically labeled “OpenType” with an .otf extension. Many well-known font vendors ship these fonts almost exclusively.
Here’s a waterfall test that uses Jos Buivenga’s Calluna font, a beautiful serif text font that can be used as a downloadable font. In the lower part of the page is the same waterfall with Constantia, one of Microsoft’s ClearType fonts that ships with Vista and Windows 7. Below is a comparison of the default rendering now under XP and Windows 7 and the rendering with the patch Bas is working on:
At very low sizes (e.g. 6px – 9px), the text drawn with the DirectWrite API is much more readable. The reason for this is clearer if you zoom in closely and look at the pixels.
Small text (6px – 8px) drawn with Windows 7 GDI ClearType rendering:
The same text drawn with DirectWrite:
Up close neither looks great but slide your chair back a few feet; the text rendered with GDI looks awful and is barely readable, the text rendered with DirectWrite legible. The default GDI rendering doesn’t do subpixel antialiasing so the glyphs appear less defined, they look thinner.
Great stuff!! Hats off to Bas!
Note: platform API’s on Mac OS X and Linux already do a good job rendering Postscript CFF fonts, this just brings them up to parity under Windows 7.