Toms Online Notebook Sharing my stuff.

The default window titlebars in Gnome on Fedora 26 ar too fat (thick), so I wanted to reduce their size.

They are config'd in the Themes (/usr/share/Themes or ~/.themes) gtk.css
OR
in a CSS file in ~/.config/gtk-3.0/gtk.css

The desktop icon text was not working with my background, so this is what I added to gtk.css to edit the color

.nautilus-desktop.nautilus-canvas-item {
color: #ddf;
text-shadow: 1 1 alpha (@fg_color, 0.8);
}

Then use tweak tool to change the theme, then change it back to reload it.

Mine now looks like this

 /* https://ask.fedoraproject.org/en/question/10035/shrink-title-bar/ */
/*
headerbar.default-decoration {
 padding-top: 3px;
 padding-bottom: 3px;
 min-height: 0px;
 font-size: 0.6em;
}

headerbar.default-decoration button.titlebutton {
 padding: 0px;
 min-height: 0px;
}
*/

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;
}

 Essentially, it was the headerbar

changing the padding, font-size, etc, to your liking.

You should also checkout the pre-made GTK3 themes like Minwaita at https://www.gnome-look.org/browse/cat/135/