< Development‎ | Tutorials
Revision as of 19:42, 28 August 2011 by Tstaerk (talk | contribs)



When you create your own KDE application you will probably want icons in it like this:


This article shows you how to do this on the example of the software krep. In case of a cmake based project you will need to

How to use icons in a qmake base project is discussed elsewhere.

When trying to add an icon to your program, you will realize there is a lot of wording against common sense. You will see the classes, KIconLoader, KIconEngine, QIconEngine, QIcon and KIcon that all seem to mean the same thing, an icon.

Analyzing the KApplications

Maybe you have already searched for yourself how a KDE application finds its icons. You will not be successful like this:

# strace -e open ktimetracker 2>&1 | grep icon
open("/usr/lib64/libkemoticons.so.4", O_RDONLY) = 3

You see, a KDE application (in this case ktimetracker) does not open icon files or even look for them. However, it spawns a process to look for these icons:

linux-qgla:~/repos/kdepim/ktimetracker # strace -ffe open ktimetracker 2>&1 | grep icon
open("/usr/lib64/libkemoticons.so.4", O_RDONLY) = 3
[pid  3457] open("/root/.icons/DMZ/cursors/left_ptr", O_RDONLY) = -1 ENOENT (No such file or directory)
[pid  3457] open("/root/.icons/DMZ/index.theme", O_RDONLY) = -1 ENOENT (No such file or directory)
[pid  3457] open("/usr/share/icons/DMZ/cursors/left_ptr", O_RDONLY) = 10
[pid  3457] open("/var/tmp/kdecache-root/icon-cache.kcache", O_RDWR|O_CREAT|O_CLOEXEC, 0666) = 10
[pid  3457] open("/var/tmp/kdecache-root/kpc/kde-icon-cache.data", O_RDONLY|O_CLOEXEC) = 10
[pid  3457] open("/var/tmp/kdecache-root/kpc/kde-icon-cache.index", O_RDONLY|O_CLOEXEC) = 10

Your KDE project

If you have a KDE project and want to use icons within it, and want that these icons install seamlessly, you will have to name the icons after the project. In the following we look at a project named krep. The important lines in CMakeLists.txt are the ones printed bold below:

PROJECT( krep )

SET(krepSources main.cpp krep.cpp krep.h)

qt4_add_dbus_adaptor( krepSources 
                      MainAdaptor )

kde4_add_ui_files( krepSources krepui.ui )

kde4_add_app_icon( krepSources "hi*-app-krep.png" )

KDE4_ADD_EXECUTABLE( krep ${krepSources} )



kde4_install_icons( ${ICON_INSTALL_DIR} )

How to test it

  • delete a file
rm /usr/local/share/icons/hicolor/22x22/apps/krep.png 
  • delete your cache
rm -rf /var/tmp/kdecache-user/
  • relogin

using this test case I could remove one icon after the other, 22x22, 64x64, 48x48, but when I removed 32x32, the icon disappeared from my application. This was the last icon that existed. Then I put in the 64x64 icon and the application carried an icon again. This means you can use any icon of 16x16, 22x22, 32x32, 48x48, 64x64, 128x128.

This page was last edited on 29 May 2019, at 22:47. Content is available under Creative Commons License SA 4.0 unless otherwise noted.