zerohour has very good tutorial about CSS styling in GTK3
thanks zerohour - you made a good job.
however I had some problems ( solved ) and want to share with you, it can help someone :-)
there is style-property for specific widget and style-property inherit in CSS
and there are also properties from parent widgets in widgets hierachy
for example: GtkEntry
widget has explicite only four style-properties:icon-prelight
Once more, if we looking at object hierarchy, there is GtkWidget as parent object for GtkEntry.
It has these style-properties: cursor-aspect-ratio
but I can set FONT or COLOR style-property for GtkEntry
it is obvious that FONT or COLOR are inherit from CSS style-properties
and finaly - and this is the issue I want to share with you,
care must be taken in which order you set properties in external CSS file.
if you have both GtkEntry and GtkSpinButton in a single form
and put something like this:
font: Serif 14;
font: Serif 24;
then you will get what you are planning: small blue entry and big red spin.
If you reverse order - you will get both widget small blue font,
Now it is obvious that PARENT object comes first,
then CHILD object in hierarchy comes second.