gtk.css

.header-bar.default-decoration {
    padding-top: 1px;
    padding-bottom: 1px;
    font-size: 0.5em;
}
.header-bar.default-decoration .button.titlebutton {
    padding: 0px;
}
 
window.ssd headerbar.titlebar {
    padding-top: 1px;
    padding-bottom: 1px;
    min-height: 0;
}
window.ssd headerbar.titlebar button.titlebutton {
    padding: 0px;
    min-height: 0;
    min-width: 0;
}
 
headerbar {
    min-height: 0px;
    padding-top: 2px;
    padding-bottom: 1px;
    padding-right: 1px;
    padding-left: 1px;
}
 
headerbar entry,
headerbar spinbutton,
headerbar button,
headerbar separator {
    margin-top: 0px;
    margin-bottom: 0px;
}
 
.titlebar {
    min-height: 0px;
}