Ada95 Binding for ncurses
by Jürgen Pfeifer.
- This document describes Version 01.00 of the binding.
- The functionality is modeled 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
- Ada programs are supposed to be readable. One of my
favorite 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-to-one interface mapping. It is
close to one-to-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-to-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
- 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
- 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.
Behind the abstraction
All the new types like Window,
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
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.
Enumeration 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.
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
I'm quite sure I forgot something.