pin libgdk is provided by the Gtk3 package
libgdk-x11-2.0.so belongs to gtk2+
~ $ pkg_info -Fe /usr/pkg/lib/libgdk-x11-2.0.so.0
gtk2+-2.24.33nb11
According to racket documentation, Platform Dependencies, dracket attempted to use gtk2+ after looking for gtk3+ libraries and finding none.
But how did it even compile in the first place without the required dependencies? Are raco packages distributed as precompiled platform-independent bundles?
Anyway, dracket depends on gtk2/3+ (for libgdk), and optionally on glib2 (for libgio) and Mesalib (for libGL). This is a quite long list of dependencies (recursively speaking), and I don't think it fits lang category.
If racket includes a GUI IDE, in my opinion the package should be split, by adding a Makefile.common in lang/racket and reference it in a hypothetical editors/dracket package.
I noticed that the whole distribution of lang/racket is quite heavy as it is now, so we should probably attempt to modularize it in future (starting from dracket). And I think this implies getting more pkgsrc contributors interested in lisp dialects (I noticed multiple threads on pkgsrc-users regarding racket, sbcl and other lisp related content recently).
Returning to @netbsdnoob's issue....
What happens if you install gtk2/3+, glib2 and Mesalib?