# 11 Commonly used libraries

In this chapter we document some of the libraries from the `<pcehome>/prolog/lib` XPCE/Prolog library. The libraries described here are only the commonly used ones. For more information check the file `Overview` in the library directory and the source-code of the library.

- Asking a filename This library defines the object @finder, instance of finder. The finder allows for asking filenames.

- Show help-balloon The library `library(help_message)` registers balloon-text with graphical objects.

- Dialog utilities Toolbars and reporting facilities. Includes example code for an application framework.

- Table-of-content like hierarchies This library extends class tree, displaying a modern-style hierarchy inside a window. This library is used for displaying the VisualHierachy and ClassHierarchy tools of the XPCE manual toolkit. See chapter 3.

- Tabular layout Primitives for dealing with tables.

- Plotting graphs and barcharts This section describes a number of libraries providing primitives for drawing graphs and barcharts.

- Multi-lingual applications Discusses support for multi-lingual applications.

- Drag and Drop Interface This library allows for drapping objects within one XPCE application.

- Playing WEB (HTTP) server Class httpd is a subclass of socket that deals with the HTTP protocol. It allows XPCE to act as a web-server.

- Document rendering Primitives for rendering mixed text/graphics, handling fonts, alignment, tables and other common text-layout primitives.

## Section Index