Ada95 Binding for ncurses

Permission is hereby granted to reproduce and distribute this binding by any means and for any fee, whether alone or as part of a larger distribution, in source or in binary form, PROVIDED this notice is included with any such distribution, and is not removed from any of its header files. Mention of ncurses and the author of this binding in any applications linked with it is highly appreciated.
This binding comes AS IS with no warranty, implied or expressed.

General Remarks

This document describes Version 00.92.00 of the binding.
The functionality is modelled to be compatible with the ncurses package, a clone of the SVr4 curses model.
I did the development on an Intel box running Linux 1.3.x and 2.0, ncurses-1.9.9e and the GNU Ada Translator gnat-3.05. For any older versions of ncurses and gnat it will not work.
You must have the m4 macroprocessor to build this package. If you don't have this program, you can get the FSF version here.
Ada programs are supposed to be readable. One of my favourite methods to make code readable is to use expressive names for the identifiers. You can find a list of a mapping of the cryptic curses names to the Ada names in this table.
This is not a typical one-2-one interface mapping. It is close to one-2-one on the functional level. Each (n)curses function has it's counterpart with a more or less similar formal parameter list in the binding. It is not one-2-one with respect to the datatypes. I tried to make records out of the flat chtype and similar structures, so you don't have to do bit operations to mark an attributed character as bold. Just make the boolean member bold of the record true. The binding also hides the structures like WINDOW, PANEL, MENU, FORM etc. ! It's a pure functional API.
I try to do as much error checking as possible and feasible in the binding. I will raise an Ada exception when something went wrong in the low-level curses. This has the effect that - at least first time in my life - (n)curses programs have now a very rigid error checking, but - thanks to Ada - you don't have to code the orgiastic error checking style of C.
Support for wide characters is currently not in the binding, as it is not really in ncurses at this point in time.

Limitations

I provide no SCREEN datatype and functions to set a new screen. If you need this (mostly for debugging I guess), write a small C routine doing all this and import it into your Ada program.
I provide no functions to switch on/off curses tracing options. Same suggestion as above.
Although Ada95 is an OO Language, this binding doesn't provide an OO abstraction of the (n)curses functionality. As mentioned above it's a thin binding for the (n)curses functions. But without any doubt it would be nice to build on top of this an OO abstraction of (n)curses functionality.
If you use the user-pointer mechanism for most of the ncurses structures in a mixed language environemt, i.e. Ada95 and C routines operate on the same objects, care must be taken because the Ada binding itself uses the user pointer mechanism for it's own purposes. See the corresponding section in implementention details.
I currently do not support the link_fieldtype functionality of the forms subsystem.
The *_IO packages are currently output only.

Hierarchy of packages

Terminal_Interface
- Curses

Implementation Details

Behind the abstraction

All the new types like Window, Panel, Menu, Form etc. are just opaque representations of the pointers to the corresponding low level (n)curses structures like WINDOW *, PANEL *, MENU * or FORM *. So you can safely pass them to C routines that expect a pointer to one of those structures.

Item and Field Arrays

In C you have to pass the item and field arrays to define menus or forms terminated by a null item or null field. This is not necessary in this binding. The binding routines will construct from an Ada95 style array of Item or Field objects internally the properly terminated array of C structure pointers. See the examples for more details.

Extended ripoffline() usage

The official documentation of (n)curses says, that the line parameter determines only whether or not exactly one line is stolen from the top or bottom of the screen. So essentially only the sign of the parameter is evaluated. ncurses has internally implemented it in a way, that uses the line parameter also to control the amount of lines to steal. This mechanism is used in the Rip_Off_Lines routine of the binding.

Using other Ada compilers

This should basically not be a problem, but you have to replace a code sequence in package Terminal_Interface.Curses.Forms that uses a hashing package supplied with the GNAT runtime, which is not part of the Standard Ada runtimes. This should not be too hard. I intend to remove this dependency in the future.

Port to other curses implementations

Basically it should not be too hard to make all this run on a regular SVr4 implementation of curses. The problems are probably these:

ncurses has some additional features which are presented in this binding. You have two choices to deal with this:
- Emulate the feature in this binding
- Raise an exception for non implemented features
Most likely you will follow a mixed approach. Some features are easy to simulate, others will be hard if not impossible.
For menu items, the name and descriptions are internally copied by ncurses. So the binding doesn't care for the lifetime of the strings passed to the construction routine for items. This assumption is not true in most other implementations of the menu library. In this case you have to modify the binding routine New_Item to safestore the strings.

I'm quite sure I forgot something.