Development/Tutorials/Icons

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

These icons are called KIcons. 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

• modify main.cpp (as it is typically called)
• modify CMakeLists.txt

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

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 )
FIND_PACKAGE( KDE4 REQUIRED )
INCLUDE_DIRECTORIES( ${KDE4_INCLUDES} . )

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

qt4_add_dbus_adaptor( krepSources 
                      org.kde.krep.xml
                      krep.h
                      krep
                      mainadaptor
                      MainAdaptor )

kde4_add_ui_files( krepSources krepui.ui )

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

KDE4_ADD_EXECUTABLE( krep ${krepSources} )

TARGET_LINK_LIBRARIES( krep ${KDE4_KPARTS_LIBS} )

install( TARGETS krep ${INSTALL_TARGETS_DEFAULT_ARGS} )

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/icon-cache.kcache 

According to Development/CMake/Addons_for_KDE#Macros you need to provide a 128x128 pixels icon.

The icon naming scheme

Example for icon names:

• hisc-apps-bla.svgz will be installed e.g. to /usr/local/share/icons/hicolor/scalable/apps/./bla.svgz. hi stands for "hicolor", sc for "scalable", apps for "applications", bla for the application's name and .svgz is the suffix for gzipped scalable vector graphic files.
• hi128-app-ktimetracker.png will be installed e.g. to /usr/share/icons/hicolor/128x128/apps/ktimetracker.png. hi stands for "hicolor", 128 for a resolution of 128x128 pixels, app for "applications", ktimetracker for the application's name and .png is the suffix for portable network graphic files.

example application

In this chapter we will build an example application kicons that looks like this:

You can obtain its source code as part of kdeexamples by calling

git clone git://anongit.kde.org/kdeexamples

files

The example application consists of

• main.cpp

just taken from the KAction example

• mainwindow.cpp

Note the command clearAction->setIcon(KIcon("tutorial-kicon")); that sets the icon

• mainwindow.h

just taken from the KAction example

• world.svg

This is a file that defines our icon in (almost natural) english language. It is a scalable vector graphics. Before being used, it must be converted to a zipped scalable vector graphic file hisc-apps-tutorial-kicon.svgz, see below.

• tutorial-kiconui.rc

just taken from the KAction example

• hisc-apps-tutorial-kicon.svgz

sorry for the name, but there are naming conventions. Create this file with the command convert from the ImageMagick package convert world.svg hisc-apps-tutorial-kicon.svgz

• CMakeLists.txt

Note the commands kde4_install_icons(${ICON_INSTALL_DIR}) and kde4_update_iconcache() which integrate the icons.

build it

To compile, link and install the example application, do a

cmake . && make && make install

To run it, call

tutorial-kicon

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
[...]

See also

• Development/Tutorials