The X Render Extension provides a new glyph rendering architecture based on client-side glyph and font management. While this resolves many tough technical issues relating to the extension design, it places the burden of rasterizing, configuring and customizing font usage on every X client.
The Xft library was written to provide X applications a convenient interface to the FreeType font rasterizer and the Render extension. As FreeType provides for no configuration or customization, Xft also performs this task. Xft provides new font naming conventions, sophisticated font matching and selection mechanisms and sufficient abstrations to permit common applications to benefit from Render extension based text output while still working on X servers without support for this extension.
XFree86 Technical Conference 2001