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Advanced Tweaks

Tweaking GTK3 applications with additional CSS

GTK3 is based on CSS and can be extended this way too. You can specify overrides in ~/.config/gtk-3.0/gtk.css that will take precedence over the active GTK3 theme.

HINT: You can start any GTK3 application via GTK_DEBUG=interactive <application> and get an interactive debug UI where you can try identifying class names of various parts of an application to access them in CSS.

Example: add space around content in terminals

Most GTK3-based terminals will use VTE. In your ~/.config/gtk-3.0/gtk.css you can add the following to add additional space around the terminal content:

VteTerminal, vte-terminal {
  padding: 4px;
}

Example: change padding in Thunar's bread-crumb path bar

.thunar .path-bar-button {
    padding: 2px 6px 2px 6px;
}

Changing the GTK3 colors of Breeze

NOTE: The following will only change colors for the GTK3 Breeze theme and won't affect the GTK2 counterpart due to its technical limitations.

Despite being a Qt style, Breeze also provides a matching GTK2+GTK3 theme. For example, on Debian-based systems (including Ubuntu) this is provided by the package gtk3-engines-breeze. The GTK3 theme of Breeze supports being recolored. This is what KDE/Plasma uses to sync its color scheme to GTK3 applications if Breeze is used. It is possible to manually recreate this behavior outside of KDE/Plasma.

NOTE: If you use KDE/Plasma's control panel (systemsettings) to change the Qt color scheme, KDE/Plasma will overwrite ~/.config/gtk-3.0/colors.css by itself. If you have KDE/Plasma installed, you can use that instead of configuring this manually as shown below.

  1. Create ~/.config/gtk-3.0/gtk.css if it doesn't exist and add the following line:

    @import 'colors.css';

  2. Create ~/.config/gtk-3.0/colors.css if it doesn't exist and insert the following content:

    @define-color theme_button_decoration_focus_backdrop_breeze #88cc00;
@define-color theme_button_decoration_focus_backdrop_insensitive_breeze #88cc00;
@define-color theme_button_decoration_focus_breeze #88cc00;
@define-color theme_button_decoration_focus_insensitive_breeze #88cc00;
@define-color theme_button_decoration_hover_backdrop_breeze #88cc00;
@define-color theme_button_decoration_hover_backdrop_insensitive_breeze #88cc00;
@define-color theme_button_decoration_hover_breeze #88cc00;
@define-color theme_button_decoration_hover_insensitive_breeze #88cc00;
@define-color theme_hovering_selected_bg_color_breeze #cce993;
@define-color theme_selected_bg_color_breeze #88cc00;
@define-color theme_view_active_decoration_color_breeze #88cc00;
@define-color theme_view_hover_decoration_color_breeze #88cc00;

  3. Replace #88cc00 with an accent color of your choice, preferably matching your kdeglobals/qt5ct colors.

HINT: The example above only changes accent colors. It is possible to adjust all other colors as well, see the full example in the appendix.

You'll need to restart GTK3 applications for the new colors to apply after adjusting them. Make sure your GTK3 is set to either "Breeze" or "Breeze-Dark" for this to work, e.g. as Net/ThemeName in your xsettingsd configuration.

Per-Session Theming

Most tools described so far can be set up in a way that their configuration does not interfere with other sessions if you have several DEs/WMs installed. You can check environment variables like XDG_CURRENT_DESKTOP or XDG_SESSION_DESKTOP within session startup files to figure out which DE/WM is running and redirect paths accordingly. See the example in the appendix below for illustration on how to use this.

xsettingsd

xsettingsd supports specifying a path to the configuration file, so you can simply have dedicated configuration files per session and select them during startup.

Autostart example:

xsettingsd -c $HOME/.xsettingsd-openbox

qt5ct, Breeze

A lot of Breeze configuration originates from ~/.config/kdeglobals, which you can turn into a symlink. The additional configuration for qt5ct resides in ~/.config/qt5ct/, which is a directory but can be a symlink as well.

# move existing configuration to new name
mv ~/.config/kdeglobals ~/.config/kdeglobals.default
mv ~/.config/qt5ct/ ~/.config/qt5ct.default/
# turn into symlinks pointing to new names
ln -sfn ~/.config/kdeglobals.default ~/.config/kdeglobals
ln -sfn ~/.config/qt5ct.default/ ~/.config/qt5ct/

Both of them are now symlinks and behave just as before:

~/.config/qt5ct -> ~/.config/qt5ct.default
~/.config/kdeglobals -> ~/.config/kdeglobals.default

The advantage of symlinks is, you can relink them anytime using ln -sfn without moving actual files around, so you can switch over to different files by relinking them during login:

# create empty if not existing
touch $HOME/.config/kdeglobals.custom
mkdir -p $HOME/.config/qt5ct.custom
# relink
ln -sfn $HOME/.config/kdeglobals.custom $HOME/.config/kdeglobals
ln -sfn $HOME/.config/qt5ct.custom $HOME/.config/qt5ct

See the example seeing this in action using the session startup mechanism described below.

nitrogen

NOTE: nitrogen will not accept symlinks of its configuration. Thus, a different approach is necessary.

Nitrogen uses the XDG_CONFIG_HOME environment variable. You can redirect the configuration location by setting this environment variable in front of the nitrogen command in your autostart and script commands.

Autostart example:

DISPLAY=:0 XDG_CONFIG_HOME=$HOME/.config/openbox nitrogen \
    --force-setter=xinerama --restore

Setting a wallpaper via nitrogen's GUI:

DISPLAY=:0 XDG_CONFIG_HOME=$HOME/.config/openbox nitrogen \
    --force-setter=xinerama

Setting a wallpaper on the command line or in a script:

export MONITOR=0
DISPLAY=:0 XDG_CONFIG_HOME=$HOME/.config/openbox nitrogen \
    --force-setter=xinerama --save --head=$MONITOR --set-zoom-fill "$1"

$1 is the first argument passed to a script, which should be the file path to the image.

NOTE: The --force-setter=xinerama parameter is for proper multi-screen support with current Intel iGPUs. You might need a different --force-setter parameter depending on your environment. See nitrogen --help.

Session Startup Files

The following files can be used as autostart scripts independently of the DM or WM used.

NOTE: Most desktop environments (DEs) and some window managers (WMs) offer their own autostart mechanisms. The files stated below will be active additionally and be executed before the DE-/DM-specific ones.

If you use any DM (e.g. lightdm, sddm etc.) you will want to opt for ~/.xsessionrc.

The ~/.xinitrc

  • executed by xinit
    • usually invoked by startx
  • for setting up GUI-related settings
    • e.g. xrdb, xmodmap or xkbcomp

First you log in on a text console, then you start the GUI with startx.

The ~/.xsessionrc

  • executed by X startup scripts on a GUI login
    • applies to all session types and Display Managers
  • also executed from startx if there's no .xinitrc
    • because startx falls back on the same session startup scripts used for GUI login
  • executed relatively early, before starting any program such as key-agent, D-Bus daemon etc.
  • typically sets up variables that may be used by later startup scripts

NOTE: You may use the .xsessionrc to startup programs (like nm-applet) and setup X11 resources (e.g. xrdb -merge) if you want to be DE/WM agnostic for autostart.

The ~/.xprofile

  • very similar to .xsessionrc but exclusively used by GDM (Gnome Display Manager)

The ~/.xsession

  • executed when logging in to graphical mode (using a Display Manager) and the custom session type is selected
  • its role is to both set login-time parameters and to start GUI session
  • a typical .xsession is 
    #!/bin/sh
. ~/.profile
. ~/.xinitrc

The ~/.profile

  • called by the default shell upon login
    • login here means when a new shell is spawned, which is usually the case for each terminal window opened

WARNING: Since ~/.profile is executed for each shell session (e.g. when you open a new terminal window or tab), it is not recommended to put any autostart commands in here!