How to set titlebar hight?

[SethWen]

The titlebar is too hight, but I can not find where to reset it.

[FraPsiZeta]

Add a file (if you don't have it already) in ~/.config/gtk-3.0/ named gtk.css with the following (you can tweak the parameters as you like, but this one seems pretty pleasing to me):

window.ssd headerbar.titlebar {
    padding-top: 1px;
    padding-bottom: 1px;
    min-height: 0;
}

window.ssd headerbar.titlebar button.titlebutton {
    padding-top: 1px;
    padding-bottom: 1px;
    min-height: 0;
}
/* shrink headebars */
headerbar {
    min-height: 38px;
    padding-left: 2px; /* same as childrens vertical margins for nicer proportions */
    padding-right: 2px;
}

headerbar entry,
headerbar spinbutton,
headerbar button,
headerbar separator {
    margin-top: 2px; /* same as headerbar side padding for nicer proportions */
    margin-bottom: 2px;
}

/* shrink ssd titlebars */
.default-decoration {
    min-height: 0; /* let the entry and button drive the titlebar size */ 
    padding: 2px
}

.default-decoration .titlebutton {
    min-height: 26px; /* tweak these two props to reduce button size */
    min-width: 26px;
}