Show default property values in documentation
When you use widget, you usually change some properties of it. Some properties have enum or boolean values, so there are few different values of it. Sometimes default value is just what you need, so you don't have to set it. But you just can't find it out because there are no default values in documentation.
Default values are defined in C code. They also was shown in old GTK Doc. So it's possible to bring them back.