I would like to know where can I find the source code of the gtk-demo-application.

I found the gtk-demo source code, but not from gtk-demo-application.
I would like to know where can I find the source code of the gtk-demo-application.

I found the gtk-demo source code, but not from gtk-demo-application.
The gtk-demo-application is in the gtk-demo directory of the GTK source code repository: