A new libpng API is added, that allows applications to access and control the libpng data structures from within a Zlib stream.
The FT_Bitmap structure (and related types) is now a base structure in the API, from which all TrueType glyph bitmaps are allocated.
The TrueType driver now uses the OpenType layout tables to select the glyphs, instead of the native Bitmap. The new interface for OpenType layout tables is used internally by the driver.
The FT_TrueTypeGX_VALIDATE_DECODE validation API (specification) is extended and replaced by a new API that doesn't depend on Adobe's original FT_TrueTypeGX_VALIDATE_DEVICE API, but provides the same functionality. The new interface is less powerful, but is completely portable between different TrueType fonts.