How to change Gtk.Notebook Tabs

Question

There is a way to change the default Gtk.Notebook Tab? I want to realize a flat tab button

Solution

Here's a minimal testcase where the notebook is being styled with CSS.

from gi.repository import Gtk, Gdk

CSS = """
.myNotebook tab {
    background-color: red;
}
.myNotebook tab:active {
    background-color: blue;
}

"""

class TestWindow(Gtk.Window):
    def __init__(self):
        Gtk.Window.__init__(self)
        self.resize(600, 400)
        self.connect("delete-event", Gtk.main_quit)

        cssprovider = Gtk.CssProvider()
        cssprovider.load_from_data(CSS)
        screen = Gdk.Screen.get_default()
        stylecontext = Gtk.StyleContext()
        stylecontext.add_provider_for_screen(screen, cssprovider,
                                             Gtk.STYLE_PROVIDER_PRIORITY_USER)

        nb = Gtk.Notebook()
        context = nb.get_style_context()
        context.add_class("myNotebook")
        for x in range(1, 5):
            label = Gtk.Label("page %s" % x)
            nb.append_page(label, None)

        self.add(nb)
        self.show_all()

if __name__ == "__main__":
    test = TestWindow()
    Gtk.main()

This only changes the background color of the tabs, but more should be possible. Here is the style for the default Ubuntu theme, you're probably searching for the border-image.

.notebook tab {
    background-image: none;
    background-color: transparent;
    border-style: solid;
    border-image: -gtk-gradient (linear, left top, left bottom,
                                 from (alpha (shade (@bg_color, 0.9), 0.0)),
                                 to (shade (@bg_color, 0.9))) 1;
    border-image-width: 0 1px;
    border-color: transparent;
    border-width: 0;
    box-shadow: none;
    /*color: shade (@fg_color, 1.2);*/
}

.notebook tab:active {
    border-color: shade (@bg_color, 0.82);
    border-style: solid;
    border-width: 1px;
    background-color: shade (@bg_color, 1.02);
    background-image: none;
    /*box-shadow: inset 0 1px shade (@bg_color, 1.1);*/

    color: @fg_color;
}

Instead of CSS classes, you can also use the GTK widget name to apply the custom style to all widgets. Remove the context.add_class("myNotebook") and use the following CSS:

CSS = """
GtkNotebook tab {
    background-color: red;
}
GtkNotebook tab:active {
    background-color: blue;
}

"""

Or work with custom names. Add a name to your widget: nb.set_name("myNotebook") And the CSS:

CSS = """
GtkNotebook#myNotebook tab {
    background-color: red;
}
GtkNotebook#myNotebook tab:active {
    background-color: blue;
}

"""

Comments

[Timo]

What is a "flat tab button"?

[koMah]

My intent was to realize a Gtk.Notebook with custom button shapes. I dont't wont do add a label, or a widget inside tabs, i want to change the tab button completely

[koMah]

Thanks for your answer, I prefer subclassing widgets but this method works as well. I know that in ubuntu, themes are stored in /usr/share/themes/, but can you tell me the filenames with this lines?

[Timo]

Subclassing isn't going to help you with theming though. The file is located here /usr/share/themes/Ambiance/gtk-3.0/gtk-widgets.css from line 1174 on my system.