Adds a style provider to this, to be used in style construction.
Note that a style provider added by this function only affects the style of the widget to which this belongs. If you want to affect the style of all widgets, use [[email protected]_provider_for_display].
Note: If both priorities are the same, a `GtkStyleProvider` added through this function takes precedence over another added through [ [email protected]_provider_for_display].
| this |
a `GtkStyleContext` |
| provider |
a `GtkStyleProvider` |
| priority |
the priority of the style provider. The lower it is, the earlier it will be used in the style construction. Typically this will be in the range between gtk_style_provider_priority_fallback and gtk_style_provider_priority_user |