Features porting older versions of GTK

It so happened that in Habré most topics are of a narrative nature. But I want to ask a question.
Can you, dear users, help with information?
I need to describe the features of ... porting GTK to other platforms! I understand that GTK is a cross-platform library, but was this also related to the earliest versions?
I need to describe the pitfalls and features that have arisen during porting.
The most chic will be if someone shares information about porting GTK under SPARC.
I will be glad and links and just effusions in the comments.
GTK has not found relevant information in the documentation yet.
Thank!