This chapter does not contain libraries that are required to run X. It does contain libraries that enhance X. The enhancement is as simple as font support or as complex as libraries that sit between X and applications that run on X whose purpose is to standardize the look and feel and interprocess communications so that applications written by different programmers end up looking and acting similarly. They also assist programmers by suppling common elements. &freetype2; &fontconfig; &qt; >K; &Pango; &ATK; >K2; &lesstif; &startup-notification;