Xft

For X11's first fifteen years, fonts lived on the server, named in XLFD and mostly as bitmaps. Xft turned that around. The application reads its own TrueType and OpenType files through FreeType, rasterises the glyphs with anti-aliasing or subpixel rendering, and ships the finished images to the server via the Render extension. Picking the file is fontconfig's job; it arrived in 2002 and understands queries like "a sans-serif that has Cyrillic".

The difference was visible at once. KDE and GTK switched over in the early 2000s, and the jagged menus that had been the Linux desktop's trademark were gone within a few years. The cost was that X's network transparency got a little less elegant: fonts now had to exist where the program ran, not where the user sat.