Re: How to find CSS style syntax changes between Gtk 3.12 and Gtk 3.22

[Emmanuele Bassi <ebassi gmail com>]

On 2017-05-08 at 13:57, Richard Shann wrote:
> On Mon, 2017-05-08 at 12:28 +0100, Emmanuele Bassi wrote:

> > > But I will have to wait for
> > > Debian to catch up with Gtk 3.20 before I can seriously look at this.
> >
> > And this is why I suggest you use a CSS class, instead;
>
> Is that something different from the GtkWidgetClass that the widget has?

CSS classes are not related to widget classes.

https://developer.mozilla.org/en-US/docs/Web/CSS/Class_selectors

> Are there a gtk_css_class_new() and a gtk_widget_assign_css_class()
> functions to use them?

You want `GtkStyleContext` and `gtk_style_context_add_class()`:

https://developer.gnome.org/gtk3/stable/GtkWidget.html#gtk-widget-get-style-context
https://developer.gnome.org/gtk3/stable/GtkStyleContext.html#gtk-style-context-add-class

> I'm completely at sea.

You probably want to read the API reference, then:

https://developer.gnome.org/gtk3/stable/theming.html

Additionally, you may want to read online resources about CSS.

> Meanwhile for anyone with an application that has
> to compile with versions of Gtk+ before and after version 3.20 here is
> the code that is currently working for me to set the background color of
> a widget:
>
> 8><8><8><8><8><8><8><8><8><8><8><8><8><8><8><8><8><8><8><8><8><8><8><8><8><
> static gchar *get_css_selector (GtkWidget *w)
> {
> static gchar *ret = NULL;
>
> #if ((GTK_MAJOR_VERSION==3) && (GTK_MINOR_VERSION>=20))
>   g_free (ret);
>   ret = g_ascii_strdown (g_strdup (g_type_name (G_TYPE_FROM_INSTANCE (w))), -1);
>   return ret+3;
> #else
>    ret = (gchar *)g_type_name (G_TYPE_FROM_INSTANCE (w));
>    return ret;
> #endif
> }

Please, don't do this.

This won't work for various widgets, and there's no guarantee it'll ever
work at all. There is *no* programmatic relationship between the CSS
element name and the type name.

For instance, `GtkRadioMenuItem` has a CSS element name called
`menuitem` and a sub-element called `radio`, with a `left` or `right`
class depending on the text direction. Thus, the selector is going to
be:

    menuitem radio { ... }

The GtkSeparatorMenuItem, on the other hand, has a single CSS element
name called `separator`.

Ciao,
 Emmanuele.

-- 
https://www.bassi.io
[@] ebassi [@gmail.com]