genxproj - embedding on X

An X11 application can be embedded in a window of another X11 application using various methods, such as XEmbed or running a pseudo X server within the window. The former needs applications to be prepared for embedding, thus can not be used with genxproj. Running an extra X server, such as xnest or xypher may be a resource-hungry operation.

Therefor genxproj chosen a third method: code injection using LD_PRELOAD. The injected code is a tiny dynamic lib that hooks the X11 function call for creating windows. Most calls are relayed to the real Xlib functions transparently, except:

the call parameters of the top window of the application is modified so that the parent window is the widget window genxproj provides
all top level window IDs are reported to genxproj so it can keep track on windows belonging to the application

In a sense genxproj is similar to a window manager: it places and sizes the main window of applications and manages hiding/showing the popup windows as well. However, it can not be implemented as a real window manager: that would suppress the user's preferred window manager.