GTypeModule provides a simple implementation of the GTypePlugin
interface. The model of GTypeModule is a dynamically loaded module
which implements some number of types and interface
implementations. When the module is loaded, it registers its types
and interfaces using g_type_module_register_type() and
g_type_module_add_interface(). As long as any instances of these
types and interface implementations are in use, the module is kept
loaded. When the types and interfaces are gone, the module may be
unloaded. If the types and interfaces become used again, the module
will be reloaded. Note that the last unref can not happen in module
code, since that would lead to the caller's code being unloaded before
g_object_unref() returns to it.
Keeping track of whether the module should be loaded or not is done by
using a use count - it starts at zero, and whenever it is greater than
zero, the module is loaded. The use count is maintained internally by
the type system, but also can be explicitly controlled by
g_type_module_use() and g_type_module_unuse(). Typically, when loading
a module for the first type, g_type_module_use() will be used to load
it so that it can initialize its types. At some later point, when the
module no longer needs to be loaded except for the type
implementations it contains, g_type_module_unuse() is called.
GTypeModule does not actually provide any implementation of module
loading and unloading. To create a particular module type you must
derive from GTypeModule and implement the load and unload functions
in GTypeModuleClass.