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

[Richard Shann <richard rshann plus com>]

On Mon, 2017-05-08 at 08:42 +0100, Emmanuele Bassi wrote:
> On 7 May 2017 at 20:57, Richard Shann <richard rshann plus com> wrote:
> > On Sun, 2017-05-07 at 19:52 +0000, Emmanuele Bassi wrote:
> > > On Sun, 7 May 2017 at 19:53, Richard Shann <richard rshann plus com>
> > > wrote:
> > >
> > >         On Sun, 2017-05-07 at 17:54 +0100, Emmanuele Bassi wrote:
> > >         > On 7 May 2017 at 16:52, Richard Shann
> > >         <richard rshann plus com> wrote:
> > >         > > I have a test program that pops up a label with a
> > >         customized
> > >         > background
> > >         > > and foreground color. This works in 3.12 using the syntax
> > >         > >
> > >         > > "GtkLabel {background-color: #FFFF00;}"
> > >         > >
> > >         > > and
> > >         > >
> > >         > > "GtkLabel {color: #FF00FF;}"
> > >         > >
> > >         > > but fails in 3.22
> > >         >
> > >         > The selector for labels is "label" since GTK+ 3.20.
> > >
> > >         Thank you very much for this. Is there a function to get the
> > >         selector
> > >         for a widget? Sort of gchar *gtk_widget_get_css_selector
> > >         (GtkWidget *w)
> > >         thing?
> > >
> > >
> > > I'm not sure what would that accomplish. Could you elaborate?
> >
> > It would enable my program to work. Currently it gets the string
> > "GtkLabel" from the type name of the widget, and that works for setting
> > the background color of various widgets in the program, replacing
> > deprecated calls.
>
> I'm still puzzled as to why you need programmatic access to the CSS
> element name.
>
> Are you generating CSS fragments from a generic function with only the
> widget type as the input?

yes

> You can use `gtk_widget_class_get_css_name()`:
>
>   https://developer.gnome.org/gtk3/stable/GtkWidget.html#gtk-widget-class-get-css-name

thanks for alerting me to this. My development system is Debian Stable,
so I don't have access to this function as it is from 3.20, however it
gave me a starting point for looking at what will be possible.

> 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)

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. But I will have to wait for
Debian to catch up with Gtk 3.20 before I can seriously look at this.

Thanks again for your responses.

Richard Shann