Optional API
The gtkmm API is meant to be easy and convenient. However, some of these conveniences are not worth the overhead on reduced resources devices, such as the Nokia 770 internet tablet. For instance, with regular gtkmm you can implement a signal handler by deriving the class and overriding its virtual on_thesignalname() method. But that additional API increases code size. And in the case of virtual methods, it increases per-object memory size, and demands that the linker loads the method's symbol even if you don't use it. Therefore, gtkmm can be built with a reduced API. In general, the optional API is rarely used, and there are slightly less convenient alternatives for all of the optional API.
When gtkmm has been built with optional API disabled, macros will be undefined, indicating that the API is not available. If you attempt to compile an application that uses this optional API, against a version of gtkmm that has disabled that API, you will see compiler warnings about missing functions.
The following sections describe the available configure options used to disable optional API. Most developers will rarely need to provide these configure options, because they will rarely build glibmm or gtkmm, preferring to use official packages or installers. However, if you are developing for an embedded device, you might need to be aware of these options.