term% cat index.txt SCRIBBLE(2) System Calls Manual SCRIBBLE(2)
NAME
scribblealloc, recognize - character recognition
SYNOPSIS
#include <u.h>
#include <libc.h>
#include <draw.h>
#include <scribble.h>
Scribble *scribblealloc(void);
Rune recognize(Scribble *);
DESCRIPTION
The scribble library implements simple character recognition. All
characters are drawn using a single stroke of the pen (mouse button 1)
as on a palmtop computer. A reference card is in /sys/src/libscrib‐
ble/quickref.gif.
The library is not really intended for standalone use. Its primary use
is by the scribble graphical control (see control(2)).
Scribblealloc allocates and returns an appropriately initialized Scrib‐
ble structure:
#define CS_LETTERS 0
#define CS_DIGITS 1
#define CS_PUNCTUATION 2
struct Scribble {
/* private state */
Point *pt;
int ppasize;
Stroke ps;
Graffiti *graf;
int capsLock;
int puncShift;
int tmpShift;
int ctrlShift;
int curCharSet;
};
This structure encodes the points making up the stroke to be recog‐
nized, as well as the character group in which the stroke should be
searched.
There are three such groups: letters, digits, and punctuation. The
current group is encoded in the curCharSet field of the Scribble struc‐
ture. Special strokes are recognized to switch between groups. In ad‐
dition, the charater recognized is influenced by mode parameters and
modifies them. These are identified by the capsLock, puncShift, tmp‐
Shift, and ctrlShift fields of the Scribble structure. When puncShift
is non-zero, the character is recognized in the punctuation character
set. Similarly, when the character recognized is printable and ctrl‐
Shift is set, the associated control character is returned as if the
control key were depressed, and when the character is a letter and cap‐
sLock or tmpShift is set, the upper-case version is returned. The
puncShift and tmpShift flags are turned off once a character has been
recognized; the others are left set.
The character to be recognized is encoded as an array of pen_points in
the ps field. To allow easy drawing of the stroke as it is drawn, the
pt and ppasize fields are available to the application code for storing
an array of points for a call to poly (see draw(2)).
Recognize recognizes the character provided in the ps field of the
Scribble structure; it returns the rune or zero if nothing was recog‐
nized.
FILES
/sys/src/libscribble/quickref.gif serves as a quick reference card.
/sys/lib/scribble/classifiers contains the stroke definitions.
SOURCE
/sys/src/libscribble
This library is adapted from software reproduced by permission:
Graffiti.c is based on the file Scribble.c copyrighted by Keith
Packard:
Copyright © 1999 Keith Packard
Permission to use, copy, modify, distribute, and sell this software and
its documentation for any purpose is hereby granted without fee, pro‐
vided that the above copyright notice appear in all copies and that
both that copyright notice and this permission notice appear in sup‐
porting documentation, and that the name of Keith Packard not be used
in advertising or publicity pertaining to distribution of the software
without specific, written prior permission. Keith Packard makes no
representations about the suitability of this software for any purpose.
It is provided "as is" without express or implied warranty.
Portions of the software Copyright © 1994 by Sun Microsystems Computer
Company.
Portions of the software Copyright © 2000 by Compaq Computer Corpora‐
tion.
SEE ALSO
Keyboard and prompter in bitsyload(1), draw(2), control(2)
SCRIBBLE(2)