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researchv10 Dan Cross

.TH LPUTCHAR 3L "630 MTG"
.SH NAME
lputchar \- 630 MTG local putchar function
.SH SYNOPSIS
.ft B
void lputchar (c)
.br
\f3char c; \f1
.ft R
.SH DESCRIPTION
\fILputchar\fR is
syntactically equivalent to the UNIX standard I/O putchar function.
It can be called by downloaded application programs who
want to display characters within their window on the 630 MTG screen.
Where (within the applications window) characters are displayed can be
affected with the \fImoveto\fR(3L) function.
.I Lputchar
calls the
.I moveto
routine to update the \fIcurrent screen point \fR after it
displays the charcter \fIc\fR.
.PP

How characters are eventually
displayed on a user's terminal when using the UNIX putchar function
is affected by the UNIX host \fIstty\fR(1) settings
and the user's terminal characteristics.
Since \fIlputchar\fR displays directly onto the 630 MTG
screen, assumptions were made about desired \fIstty\fR
settings. In general, \fIlputchar\fR does as little processing on
the output stream as practical. 
If more extensive processing of control characters is needed, it can
be accomplished as shown in the example program below.
.P
The following are the only control characters processed by \fIlputchar\fR.
All other characters will be displayed as \fBASCII\fR characters:
.TP
.B \er
Carriage Return. Move the current point to the left edge of the window.
.TP
.B \en
Newline. Move the current point down one line and to the left edge of the 
window. Scroll the window if necessary.
.TP
.B \et
Horizontal tab. Tab characters are expanded to spaces with tab stops at every
eighth space.
.SH EXAMPLE
.LP
If an application program wanted to, for example, process bells and
backspaces rather than display the \fBASCII\fR bell and backspace
characters, it could define a function \fImylputchar\fR as follows:
.PP
.RS 3
.ft CM
.S -2
.nf
#include <dmd.h>
#include <font.h>

void lputchar();
void moveto();
void ringbell();
Point sPtCurrent();

mylputchar(c)
char c;
{
	Point curpos;

	switch( c ) {
	case '\e007':
		ringbell();
		break;
	case '\eb':
		/* get the current position
		** if( not already at the left edge of the
		**	window ) {
	 	** 	move back one character position
		** 	lputchar a space to erase the last
		** 	character and move back again
		** }
		*/
		curpos = sPtCurrent();
		if(curpos.x - FONTWIDTH(largefont)
		    >= Drect.origin.x) {
			curpos.x -= FONTWIDTH(largefont);
			moveto(curpos);
			lputchar(' ');
			moveto(curpos);
		}
		break;
	default:
		lputchar(c);
		break;
	}
}
.fi
.ft R
.RE
.S +2
.SH SEE ALSO
bputchar(3L), moveto(3L), printf(3L), structures(3R).
.br
stty(1) in the \fIUNIX System V User's Reference Manual\fR.
.br
putc(3S) in the \fIUNIX System V Programmer's Reference Manual\fR.

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