Uniform look for Qt and GTK applications

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Qt and GTK+ based programs both use a different widget toolkit to render the graphical user interface. Each come with different themes, styles and icon sets by default, among other things, so the "look and feel" differ significantly. This article will help you make your Qt and GTK+ applications look similar for a more streamlined and integrated desktop experience.

Overview

To get a similar look between the toolkits, you will most likely have to modify the following:

  • Theme: The custom appearance of an application, widget set, etc. It usually consists of a style, an icon theme and a color theme.
  • Style: The graphical layout and look of the widget set.
  • Icon Theme: A set of global icons.
  • Color Theme: A set of global colors that are used in conjunction with the style.

You can choose various approaches:

  • Use a special theme engine, which intermediates the modification of the other graphical toolkit to match your main toolkit.
  • Modify GTK+ and Qt styles separately with the tools listed below for each toolkit and aim for choosing similarly looking themes (style, colors, icons, cursors, fonts).

Theme engines

A theme engine can be thought of as a thin layer API which translates themes (excluding icons) between one or more toolkits. These engines add some extra code in the process and it is arguable that this kind of a solution is not as elegant and optimal as using native styles.

QGtkStyle

Note: QGtkStyle will be removed from qt5-base 5.7 [1]. and added to qt5-qtstylepluginsAUR as name gtk2 [2]
Warning: Depending on GTK+ 2 theme, this style may cause rendering issues such as transparent fonts or inconsistent widgets.

This Qt style uses GTK+ 2 to render all components to blend in with GNOME and similar GTK+ based environments. Beginning with Qt 4.5, this style is included in Qt. It requires gtk2 to be installed and configured.

This is the default Qt4 style in Cinnamon, GNOME and Xfce, and the default Qt5 style in Cinnamon, GNOME, MATE, LXDE and Xfce. In other environments:

  • For Qt4, it can be enabled with Qt Configuration (qtconfig-qt4), choose GTK+ under Appearance > GUI Style. Alternatively, edit the /etc/xdg/Trolltech.conf (system-wide) or ~/.config/Trolltech.conf (user-specific) file:
~/.config/Trolltech.conf
...
[Qt]
style=GTK+
...

For full uniformity, make sure that the configured GTK+ theme supports both GTK+ 2 and GTK+ 3.

QGnomePlatform

This Qt 5 platform theme applies the appearance settings of GNOME for Qt applications. It can be installed with the qgnomeplatform-gitAUR package. It does not provide a Qt style itself, instead it requires a style that support both Qt and GTK+.

This platform theme is enabled automatically in GNOME since version 3.20. For other systems, it can be enabled by setting the following environment variable: QT_QPA_PLATFORMTHEME=qgnomeplatform.

Styles for both Qt and GTK+

There are widget style sets available for the purpose of integration, where builds are written and provided for both Qt and GTK+, all major versions included. With these, you can have one look for all applications regardless of the toolkit they had been written with.

Tip: You may want to apply user defined styles to root applications, see GTK#Theme not applied to root applications and Qt#Theme not applied to root applications.
Note: Since version 3.16, GTK+ 3 does not support non-CSS themes, hence previous solutions such as Oxygen-Gtk are no longer viable options.

Breeze

Breeze is the default Qt style of KDE Plasma. It can be installed with the breeze package for Qt5, the breeze-kde4 package for Qt4, and the breeze-gtk package for GTK+ 2 and GTK+ 3.

Once installed, you can use one of the many GTK+ configuration tools to change the GTK+ theme.

Adwaita

Adwaita is the default GNOME theme. The GTK+ 3 version is included in the gtk3 package, while the GTK+ 2 version is in gnome-themes-standard. adwaita-qt is a Qt port of the Adwaita theme. Unlike #QGtkStyle, which mimics the GTK+ 2 theme, it provides a native Qt style made to look like the GTK+ 3 Adwaita. It can be installed with the adwaita-qt4AUR and adwaita-qt5AUR packages for the Qt 4 and 5 versions, respectively.

To set the Qt style as default:

  • For Qt4, it can be enabled with Qt Configuration (qtconfig-qt4), choose adwaita under Appearance > GUI Style. Alternatively, edit the /etc/xdg/Trolltech.conf (system-wide) or ~/.config/Trolltech.conf (user-specific) file:
~/.config/Trolltech.conf
...
[Qt]
style=adwaita
...
  • For Qt 5, it can be enabled by setting the following environment variable: QT_STYLE_OVERRIDE=adwaita.

Tips and tricks

KDE file dialogs for GTK+ applications

Warning: Some GTK+ applications may not be compatible with KGtk-wrapper (e.g. Chromium), sometimes the wrapper makes the application crash (e.g. Firefox) and even other applications like KDM (when used with e.g. Thunderbird).

kgtkAUR from the AUR is a wrapper script which uses LD_PRELOAD to force KDE file dialogs in GTK+ 2.x apps. Once installed you can run GTK+ 2.x applications with kgtk-wrapper in two ways (using Gimp in the examples):

  • Calling kgtk-wrapper directly and using the GTK+ 2.x binary as an argument:
$ /usr/bin/kgtk-wrapper gimp
  • Modifying the KDE .desktop shortcuts files you can find at /usr/share/applications/ to prefix the Exec statement with kgtk-wrapper.
e.g. with GIMP, edit the /usr/share/applications/gimp.desktop shortcut file and replace Exec=gimp-2.8 %U by Exec=kgtk-wrapper gimp-2.8 %U.

Using a GTK+ icon theme in Qt apps

If running KDE, install kde-gtk-config and select the icon-theme under System Settings > Application Style > GTK.

If you are not using GNOME, run gconf-editor, look under desktop > gnome > interface for the icon_theme key and change it to your preference. As you are not using GNOME, it is possible that you will have to set export DESKTOP_SESSION=gnome somewhere in your ~/.xinitrc or, if you are using LightDM, in /etc/environment.

Improve subpixel rendering of GTK apps under KDE Plasma

See Font configuration#LCD filter.

Troubleshooting

Qt applications do not use QGtkStyle

Qt will not apply QGtkStyle correctly if GTK+ is using the GTK+-Qt Engine. Qt determines whether the GTK+-Qt Engine is in use by reading the GTK+ configuration files listed in the environmental variable GTK2_RC_FILES. If the environmental variable is not set properly, Qt assumes you are using the engine, sets QGtkStyle to use the style GTK+ style Clearlooks, and outputs an error message:

QGtkStyle cannot be used together with the GTK_Qt engine.

Another error you may get after launching qtconfig-qt4 from a shell and selecting the GTK+ style is:

QGtkStyle was unable to detect the current GTK+ theme.

According to this thread, you may simply have to install libgnomeui to solve this issue. This has the added benefit that you do not need to edit a file every time you change your theme via a graphical tool, like the one provided by xfce.

Users of Openbox and other non-GNOME environments may encounter this problem. To solve this, first add the following to your .xinitrc file:

.xinitrc
...
export GTK2_RC_FILES="$HOME/.gtkrc-2.0"
...
Note:
  • Make sure to add this line before invoking the window manager.
  • You can add multiple paths by separating them with colons.
  • Make sure to use $HOME instead of ~ as it will not properly expand to the user's home directory.

Then specify the theme you want in the ~/.gtkrc-2.0 file using a dedicated application or manually, by adding:

.gtkrc-2.0
...
gtk-theme-name="[name of theme]"
...

Some tools only insert the following include directive in ~/.gtkrc-2.0:

.gtkrc-2.0
...
include "/usr/share/themes/SomeTheme/gtk-2.0/gtkrc"
...

which apparently is not recognized by all versions of QGtkStyle. You can hotfix this problem by inserting the gtk-theme-name manually in your ~/.gtkrc-2.0 file like above.

Note: Style-changing applications will most probably rewrite the ~/.gtkrc-2.0 file the next time you change themes.

If these steps do not work, install gconf and run this command:

gconftool-2 --set --type string /desktop/gnome/interface/gtk_theme [name of theme]

If you further want to set the same icon and cursor theme, then you have to specify them, too.

gconftool-2 --set --type string /desktop/gnome/interface/icon_theme Faenza-Dark

This sets the icon theme to Faenza-Dark located in /usr/share/icons/Faenza-Dark. For the cursor theme you first have to set the gconf value.

gconftool-2 --set --type string /desktop/gnome/peripherals/mouse/cursor_theme Adwaita

Then you will have to create the file /usr/share/icons/default/index.theme with the following lines:

[Icon Theme]
Inherits=Adwaita

Themes not working in GTK+ apps

If the style or theme engine you set up is not showing in your GTK applications then it is likely your GTK+ settings files are not being loaded for some reason. You can check where your system expects to find these files by doing the following..

$ export | grep gtk

Usually the expected files should be ~/.gtkrc for GTK1 and ~/.gtkrc2.0 or ~/.gtkrc2.0-kde for GTK+ 2.x.

Newer versions of gtk-qt-engineAUR[broken link: archived in aur-mirror] use ~/.gtkrc2.0-kde and set the export variable in ~/.kde/env/gtk-qt-engine.rc.sh. If you recently removed gtk-qt-engine and are trying to set a GTK+ theme then you must also remove ~/.kde/env/gtk-qt-engine.rc.sh and reboot. Doing this will ensure that GTK+ looks for its settings in the standard ~/.gtkrc2.0 instead of the ~/.gtkrc2.0-kde file.