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

[Emmanuele Bassi <ebassi gmail com>]

On 8 May 2017 at 12:04, Richard Shann <richard rshann plus com> wrote:

> > But I'd strongly recommend you use CSS classes instead of styling the
> > bare element name.
> >
> > CSS selectors in GTK+ work exactly like the HTML counterpart; you can
> > style "div" or "p" directly, but it's often much more appropriate to
> > create a specific CSS class, like "green-background", and add it to
> > the widget you wish to style.
>
> I didn't find anything describing creating a GtkWidgetClass in the
> gtk3/stable documentation, it seems that there is a field in the
> GtkWidget structure pointing to such a structure accessed via
>
> GTK_WIDGET_GET_CLASS (widget)

Yes, this is part of basic GObject usage: each instance has a pointer
to its instantiating class structure.

> so I imagine that using
>
> gtk_widget_class_set_css_name (class, name)
>
> could mean you would get control over the style of that widget and any
> others whose class you assigned that name.

You don't have *control* over the style. You can *add* to the existing
style — which may include undoing what the existing style does, but
then you need to know what the style does, or essentially reset CSS
properties by using their initial state, see:
https://drafts.csswg.org/css-cascade-3/#initial

This is how CSS works. The only way for you to control the style of a
GTK+ application is to ship your own theme, and load it in place of
the user theme.

CSS is a *very* powerful set of rules for rendering content using a
declarative syntax; it's *really* not a bunch of color definitions,
like the style system in GTK+ 2.x. You will need to learn how CSS
works in order to use it.

> 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; CSS classes
work regardless of what the CSS name of a widget is.

Ciao,
 Emmanuele.

-- 
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[@] ebassi [@gmail.com]