Michael Fulbright Red Hat Software, Inc.

drmike@redhat.com

1999 Red Hat, Inc The GNOME desktop environment is built on top of numerous support libraries which handle the many tasks expected of a modern desktop. Using these libraries, the developer can build a fully integrated application that fits into the GNOME desktop seamlessly. This document provides a guide to the function and relationships among these libraries. Library Name Function libaudiofile Reads common audio file formats libgdk_imlib Loads and manipulates image formats libgtk GIMP Toolkit, widget used in GNOME libgnome GNOME utility functions libgnomeui GNOME UI utility functions libglib String functions, hashes, lists, etc libgdk Lower level drawing toolkit libesd Client interface to esound daemon Modern desktop applications demand a wide variety of services from the underlying application framework. In addition to the expectations of a widget set, programmers need tools to access and display audio and image information as well. The libaudiofile library can read a wide variety of audio file formats (AIFF, AIFC, WAV, and NeXT/Sun au). Once samples have been loaded using libaudiofile, libesd routines are available to play these samples via the Esound sound daemon. The Esound sound daemon allows several processes to access the sound hardware simultaneously. Esound is required because the Linux kernel does not allow multiple process access. Esound also supports sound over a network. Sound samples can be preloaded into Esound for later playback, which signifcantly reduces latency on network connections since the sample does not have to be repeatedly sent over the wire. GUI applications require extensive use of images to create a friendly and comfortable user interface. Traditionally it has been difficult to load all the common graphic file formats into X11 applications. The libbgdk_imlib library addresses this issue by providing convenient and powerful functions to load multiple file formats (JPEG, GIF, TIFF, PNG, XPM, PPM, PGM, PBM, and BMP). These files are converted to an internal 24 bit RGB representation, and utility functions exist to scale as well as render from 24 bit RGB to a variety of other color depths (with dithering if desired). Input image files are cached internally by libbgdk_imlib to improve performance in applications which repeatedly use images. The libgtk library is the GIMP toolkit library. It is a professional quality widget set which, in many ways, is superior to other widget sets. GNOME applications are written entirely using libgtk for all GUI elements (buttons, menus, scrollbars, etc). The libgnome library provides many utility routines related to the GNOME desktop environment. Among the capabilities provided are config file support for applications to store persistent data, support for metadata (data attached to file objects, like the icon to display for a particular file type), and support for loading help documents into the GNOME help browser. An interface is also provided so GNOME applications can talk to the GNOME session manager. Finally, routines exist to configure how different mime-types are handled by GNOME and the GNOME file manager. GNOME applications use the libgnomeui library extensively. This library contains toolkit extensions to the GTK+ widget set. Users can easily create dialog boxes, and message boxes, as well as menubars, toolbars, and status lines. An extensive array of stock icons is provided for the programmer's use in dialogs, menu entries, and buttons. Because all GNOME applications will use libgnomeui to create these common GUI elements, visual consistency is guaranteed. Another important capability provided is the GNOME canvas, which allows painless creation of complex interfaces. Similar in many ways to the Tk canvas, the GNOME canvas provides a framework to create address books, calendar applications, and spreadsheets. CORBA is a mechanism that GNOME applications can use to access services from other GNOME components. The CORBA implementation used by GNOME is called ORBit. Library Name Function libIIOP Low level CORBA communications libORBitutil Convenience routines for ORBit libORBit CORBA API libgnorba GNOME CORBA framework Applications will only access libORBit and libgnorba directly, as libIIOP and libORBitutil are used internally by ORBit. libORBit provides the implementation of the CORBA API. It is the ORB proper, and works in concert with libIIOP and the IDL compiler to provide the complete CORBA implementation to the application. ORBit provides the CORBA framework to developers for problem solving. To expedite the use of CORBA in GNOME applications specifically, additional facilities are provided by libgnorba: CORBA intialization routine for all GNOME apps, to automatically take care of security and GTK+ main loop integration. Automatic name service bootstrapping and accessing. Standard object server directory, object server registration and activation. Several other useful libraries have been created for use by GNOME applications (although most will work with non-GNOME applications as well) which can help when solving different kinds of problems. The libxml library assists in reading and parsing XML files. Several GNOME applications (glade and gnumeric among for example) use libxml when dealing with XML files. When accessing data via HTTP, the protocal used by web servers, the libghttp library can be helpful. It is designed with graphical applications in mind, so that requests can be made without block waiting on a response. This allows the graphical application to be responsive while a request is in progress. The following table maps the name of the library (which resides in /usr/lib) to the name of the package(s) which contain them: Library Name Run-time Package Development Package libaudiofile audiofile audiofile-devel libesd esound esound-devel libglib glib glib-devel libgtk gtk+ gtk+-devel libgdk_imlib imlib imlib-devel libgnome gnome-libs gnome-libs-devel libgnomeui gnome-libs gnome-libs-devel libgnorba gnome-libs gnome-libs-devel libIIOP ORBit ORBit-devel libORBitutil ORBit ORBit-devel libORBit ORBit ORBit-devel libxml libxml libxml-devel libghttp libghttp libghttp-devel The "-devel" packages are only required for actual development using the library, and end-users will only require the runtime library (the non-"-devel" packages) to be installed to run a GNOME application.