[Gambas-user] ncurses - macro is not found

[Benoît Minisini]

> Am 02.03.2011 21:21, schrieb Benoît Minisini:
> >> I do not have that much idea of how that works under C, so that's why I
> >> ask here.
> >> 
> >> In the ncurses library, there are macros. One of them is needed to get
> >> the dimensions of the "window". But when I define it
> >> 
> >> EXTERN getmaxyx(...
> >> 
> >> when my program starts, there is merely the error "cannot find symbol
> >> getmaxyx in library ncurses".
> >> 
> >> So what can I do here?
> >> 
> >> Regards
> >> Rolf
> > 
> > A macro is not a function. It is some code replaced by some other code at
> > compilation time. The "getmaxyx" identifier does not exist in the
> > executable.
> > 
> > You must read the C header file to see what the getmaxyx() macro actually
> > does.
> > 
> > The gcc compiler has the "-E" option that can help you, by writing to the
> > standard output the real code that will be compiled once all macros have
> > been expanded.
> > 
> > Regards,
> 
> Thanks for the tip. I am aware of what a macro in general does, but I do
> not understand the result of this thing:
> 
> getmaxyx(stdscr, y, x);
> 
> becomes
> 
> (y = ((stdscr)?((stdscr)->_maxy + 1):(-1)), x =
> ((stdscr)?((stdscr)->_maxx + 1):(-1)));
> 
> and I do not know what "?", "->" and ":" are good for... I guess, the
> basic functions are called maxy and maxx, but why with "_" etc...?

"x ? y : z" is an expression that returns "z" if "x" is zero, and returns "y" 
otherwise.

(stdscr)->_maxy is the value of the "_maxy" field of the structure pointed by 
stdscr.

So you must declare a structure equivalent to what stdscr points at, to be 
able to access its _maxy field, as that macro does.

Of course, a ncurses component written in C would be simpler!

Regards,

-- 
Benoît Minisini