I have tracked down the cause if this problem. On Win+Mac gtk sets the application icon directly, but on Linux it was handled by smclient which would get the icon from the .desktop. smclient support was removed, but the icon setting call was not replaced when this was done.
-- You received this bug notification because you are a member of Desktop Packages, which is subscribed to gedit in Ubuntu. https://bugs.launchpad.net/bugs/1219120 Title: gedit has no application icon Status in “gedit” package in Ubuntu: Confirmed Bug description: When running gedit in Xubuntu 13.10, the icon which should appear in the top left corner of the window, or in the task bar, is replaced by a default one. The icon in the menu and launcher is displayed correctly. See screenshot. ProblemType: Bug DistroRelease: Ubuntu 13.10 Package: gedit 3.8.3-0ubuntu3 ProcVersionSignature: Ubuntu 3.11.0-4.9-generic 3.11.0-rc7 Uname: Linux 3.11.0-4-generic x86_64 NonfreeKernelModules: nvidia ApportVersion: 2.12.1-0ubuntu2 Architecture: amd64 Date: Sat Aug 31 00:58:08 2013 InstallationDate: Installed on 2013-08-27 (3 days ago) InstallationMedia: Xubuntu 13.10 "Saucy Salamander" - Alpha amd64 (20130827) MarkForUpload: True SourcePackage: gedit UpgradeStatus: No upgrade log present (probably fresh install) To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/gedit/+bug/1219120/+subscriptions -- Mailing list: https://launchpad.net/~desktop-packages Post to : desktop-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~desktop-packages More help : https://help.launchpad.net/ListHelp