SCRIBBLE(2)

NAME

scribblealloc, recognize − character recognition

SYNOPSIS

#include <u.h>
#include <libc.h>
#include <draw.h>
#include <scribble.h>
Scribble∗scribblealloc(void);
Runerecognize(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/libscribble/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 Scribble structure:

#defineCS_LETTERS0
#defineCS_DIGITS1
#defineCS_PUNCTUATION2
struct Scribble {
/∗ private state ∗/
Point∗pt;
intppasize;
Stroke ps;
Graffiti∗graf;
intcapsLock;
intpuncShift;
inttmpShift;
intctrlShift;
intcurCharSet;
};

This structure encodes the points making up the stroke to be recognized, 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 structure. Special strokes are recognized to switch between groups. In addition, the charater recognized is influenced by mode parameters and modifies them. These are identified by the capsLock, puncShift, tmpShift, 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 ctrlShift is set, the associated control character is returned as if the control key were depressed, and when the character is a letter and capsLock 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 recognized.

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:

Permission to use, copy, modify, distribute, and sell this software and its documentation for any purpose is hereby granted without fee, provided that the above copyright notice appear in all copies and that both that copyright notice and this permission notice appear in supporting 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.

Museum