Files: scheme/glt_gui.c, scheme/glt_gui.h
For accessing GUI objects (i.e. windows), there are also
proxies, but these proxies are completely independent of kernel
proxies. GUI proxies are initialized during GUI
initialization, in the function guilelink_gui_init(). These proxies
are also implemented using smobs, but the reverse mechanism is
simpler. Each window has a slot in its structure for storing a proxy
which is initially empty. After a request for the proxy (function
window2scm), a newly created proxy is stored in this slot. If
the garbage collector finds the proxy as unusable, then this slot is reset to
empty. GUI proxies do not increase reference counters of
windows (because windows do not have reference counters), so it is
possible that window is freed sooner than its proxy. So, the destroying
method of each window calls window_proxy_clean() on the stored
proxy and this function clears the content (stored pointer) of that proxy
so that the cleared proxy is not considered valid (Scheme functions fail on
that proxy).