X11GTK
X11GTK is a software layer that integrates the GTK toolkit with the X Window System (X11) to enable GTK-based applications to render within X11 windows. The project provides an X11 backend for the GTK runtime, translating X11 input events into GTK events, mapping GTK drawing to X11 surfaces, and handling window management tasks such as sizing, focus, and decoration. It also supplies theming and font rendering capabilities consistent with GTK applications and supports standard X11 features such as clipboard, drag-and-drop, and selection.
Historically, X11GTK emerged in the early days of GTK development as a means to run GTK applications
Licensing and availability varied by version, but the project typically followed permissive or GPL-derived licenses common