libxext-dev 2:1.3.4-0ubuntu3 (armhf binary) in ubuntu impish

 libXext provides an X Window System client interface to several extensions to
 the X protocol.
 .
 The supported protocol extensions are:
  - DOUBLE-BUFFER (DBE), the Double Buffer extension;
  - DPMS, the VESA Display Power Management System extension;
  - Extended-Visual-Information (EVI), an extension for gathering extra
    information about the X server's visuals;
  - LBX, the Low Bandwidth X extension;
  - MIT-SHM, the MIT X client/server shared memory extension;
  - MIT-SUNDRY-NONSTANDARD, a miscellaneous extension by MIT;
  - Multi-Buffering, the multi-buffering and stereo display extension;
  - SECURITY, the X security extension;
  - SHAPE, the non-rectangular shaped window extension;
  - SYNC, the X synchronization extension;
  - TOG-CUP, the Open Group's Colormap Utilization extension;
  - XC-APPGROUP, the X Consortium's Application Group extension;
  - XC-MISC, the X Consortium's resource ID querying extension;
  - XTEST, the X test extension (this is one of two client-side
    implementations; the other is in the libXtst library, provided by the
    libxtst6 package);
 .
 libXext also provides a small set of utility functions to aid authors of
 client APIs for X protocol extensions.
 .
 This package contains the development headers for the library found in
 libxext6. Non-developers likely have little use for this package.
 .
 More information about X.Org can be found at:
 <URL:http://www.X.org>
 .
 This module can be found at
 git://anongit.freedesktop.org/git/xorg/lib/libXext