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### 1 Introduction and Overview

#### 1.1 Introduction

The motivation of the package Browse was to provide better functionality for displaying two-dimensional arrays of data (e.g., character tables): moving through the data without loosing row and column labels, searching for text, displaying extra information, hiding information, allowing interactive user input, ...

We wanted to achieve this by using the capabilities of the terminal emulations in which GAP is running, and not by some external graphical user interface. For this we have chosen to use the widely available C-library ncurses, see [NCu]. It contains functions to find out terminal capabilities, to change properties of terminals, to place text, to handle several windows with overlapping, ... To use these functions the terminal is switched to a visual mode so that the display of the non-visual mode of your terminal in which GAP is running is not clobbered.

Browse has now three levels of functionality:

A low level interface to ncurses

This may be interesting for all kinds of applications which want to display text with some markup including colors, maybe in several windows, using the available capabilities of a terminal.

A medium level interface to a generic function NCurses.BrowseGeneric (4.3-1)

This is for displaying two-dimensional arrays of data, handles labels for rows and columns, searching, sorting, binding keys to actions, ... If you want to implement such applications for further kinds of data, first look at the examples in Section BrowseData.IsBrowseTable (4.2-3), then check what can be copied from the examples in Chapter 6, and consult the descriptions in Chapters 4 and 5.

Applications of these interfaces

We provide some applications of the ncurses interface and of the generic NCurses.BrowseGeneric (4.3-1) function. These may be interesting for end users, and also as examples for programmers of further applications. This includes (of course) a method for browsing through character tables, functions for browsing through data collections, several games, and an interface for demos.

Users interested only in these applications should perhaps just try NCurses.Demo().

#### 1.2 Overview

##### 1.2-1 The ncurses interface

Chapter 2 describes GAP's interface to the ncurses C-library. The imported C-functions are shortly explained, but for further details we refer to the documentation of that library. There are also a few utility functions on GAP level, such as NCurses.SetTerm (2.2-2), which simplify the use of the library.

The concept of an attribute line, see NCurses.IsAttributeLine (2.2-3), helps to deal with text with markup for its display in a terminal window.

This chapter is for users who want to write their own applications of ncurses.

##### 1.2-2 Applications of ncurses

In Chapter 3 we describe some interactive applications of the ncurses interface. For example, there is NCurses.Select (3.1-2) for asking a user to choose one or several of a given list of items. There is also a demo function NCurses.Demo (3.2-1) which we use to demonstrate features of the Browse package, but it may be interesting for other kinds of demos as well.

##### 1.2-3 The interface to browse two-dimensional arrays

Chapters 4 and 5 describe the interface to a generic function NCurses.BrowseGeneric (4.3-1) which can be used for an interactive display of two-dimensional arrays of data. The first of these covers the basic functionality which may be sufficient for many applications and the second gives more technical details. With interactive display we mean that it is not only possible to scroll through the data, but one can search for strings, sort by rows or columns, select entries, bind arbitrary actions to keys and mouse events, ask for help, and more.

##### 1.2-4 Applications of the generic function NCurses.BrowseGeneric

In Chapter 6 we describe several applications which are using the generic NCurses.BrowseGeneric (4.3-1) interface introduced before. They are provided as prototype applications and so we include some implementation remarks in their documentation.

Users who just want to use these applications hopefully do not need to read this Browse manual, all applications are coming with built-in help windows.

There are different kinds of applications. First, there are methods for browsing through character tables and tables of marks (our original motivation for this package). Then there are applications for browsing through data collections, e.g., the data available through the AtlasRep package, the GAP bibliography or the sections of the GAP manuals. Finally, there are several games like Sam Loyd's fifteen puzzle (generalized), peg solitaire, and Sudoku (including functions to create new puzzles and to solve puzzles).

#### 1.3 User preferences provided by the Browse package

See SetUserPreference (Reference: SetUserPreference) for GAP's user preferences mechanism, and BrowseUserPreferences (6.10-1) for viewing and modifying user preferences.

##### 1.3-1 The user preference EnableMouseEvents

This user preference defines whether mouse events are enabled by default in visual mode (value true) or not (value false, this is the default). During the GAP session, the value can be changed using NCurses.UseMouse (2.2-10). Inside browse applications based on NCurses.BrowseGeneric (4.3-1) or NCurses.Select (3.1-2), the value can be toggled usually by hitting the key.

##### 1.3-2 The user preference SelectHelpMatches

In the case that the GAP help system finds multiple matches, true (the default) means that the user can choose one entry from a list that is shown via NCurses.Select (3.1-2), and false means that the matches are just shown in a pager.

##### 1.3-3 The user preference SelectPackageName

In the case that LoadPackage (Reference: LoadPackage) is called with a prefix of some package names, true (the default) means that the user can choose one matching entry, and false means that the matches are just printed.

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