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Ada95 Binding for ncurses
The ncurses Ada95 binding is © 1996-2000 by Jürgen Pfeifer.
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 01.00 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 the latest stable release of Linux, ncurses and the most recent released GNU Ada Translator gnat versions. For any older versions of ncurses and gnat it is not guaranteed to 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.
The only exception is the method how fieldtypes are represented in this Binding. We provide an abstract tagged type Field_Type from which the various fieldtypes are derived. - I currently do not support the link_fieldtype functionality of the forms subsystem.
- The *_IO packages are currently output only.
Hierarchy of packages
If you want to navigate through the html pages of the package specs, click here.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.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.How user defined field types work
TBDEnumeration fields handling
The (n)curses documentation says, that the String arrays to be passed to an TYPE_ENUM fieldtype must not be automatic variables. This is not true in this binding, because it is internally arranged to safely copy these values.Using other Ada compilers
This should basically not be a problem.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