What is Merlin
--------------

Merlin is a simple, small footprint single character recognition
engine originally implemented for a small Linux based
phone with limited resources. Back then it read input from a
microcontroller and fed output to the console. Then I transformed this
into an X application which generates KeyEvents to the window in
focus, suitable for small web pads with a touchscreen and an X
windowing system. But the core part which is the method "recognize"
could easily be used in other contexts or replaced if one prefers
other methods of recognition. 

Merlin currently implements online sigle character recognition using a
technique called elastic matching. There are some images in the doc
directory of the characters. No claim that this elastic matching
method should be something better or worse than anything else. It
works for me and I'm happy with that. A new user could need some
training though. Character recognition is always a compromise between
factors such as recognition rate, recognition speed, usability (how
easy it is to write the characters) and CPU and memory usage. This
implementation found a balance of these factors for the special
hardware it was targeted for in the beginning and it worked ok
there. On a fast computer with lots of memory and with a floating
point unit one could of course implement something much better. 


Howto write
------------
The window is divided into two areas. An alpha-area and a numerical
area. Large letters are written by overlapping the character over the
two regions. 

You write all simple characters without lifting the pen.

What also can be mentioned is the Extended mode which can be set by
drawing a straight line upwards. In extended mode you can then input
characters which contain more than one stroke. Several of the extended
characters is not working at the moment (in the X version of merlin)
however 'cause I could not find the keycode to generate them (which
means that Merlin will recognize them but cannot transfer them to X,
for instance, how do you write the characters (r) or (c) with a
keyboard? If you know please tell me.) 


How does it work
----------------
After recognizing a character Merlin transforms the ascii character
into a X keycode which is sent to the window in focus. This
translation can currently be done in two ways depending on what
keyboard layout you are using. It supports English keyboards and
Swedish. English is now the default layout. Remove -DUSE_ENGLISH in
Makefile if you prefer a Swedish layout. You can probably figure it
out by looking in swedish-kbd.map and edit it to fit your system if
needed. There is probably a better way to do this than to hardcode it
for a specific keyboard layout but I didn't have the time to find out. 

Merlin uses "Redirection override" to stay away from the window
manager. It makes the focus issue much nicer for instance if you're
using sloppy focus (because it would not be good if Merlin got the
focus when you write on it since it would lead to that it would send 
the "keypress" to itself). Despite of this click-to-focus is
recommended. 


Problems with some programs
---------------------------
Like all SendEvent programs like gtkeyboard and such, there are
problems with programs that refuses to accept SendEvents. Xterm and
XEmacs are two such programs. Xterm is fixed by setting the vt100
Xresource allowSendEvents or by control-clicking on an xterm and
choosing allow send events (see 'man xterm'). XEmacs is fixed by adding 
(custom-set-variables '(x-allow-sendevents t)) to your .emacs. 


Usage
------
Merlin accepts the usual X option -geometry but that's it.
If you don't specify an option Merlin will start in the upper left
corner with a 200x100-window.

Example:   merlin -geometry 200x100-10-10
           Starts Merlin ten pixels in and up from the lower right
           corner with a 200x100 - window.


Environment variables
----------------------
If you set the environment variable MERLIN_HOME to a suitable
directory merlin will look there for pattern samples instead of in the 
default directory.


Questions, bug reports etc. goes to xmerlin@hellkvist.org. Since my
time is limited I would prefer patches instead of bug reports though.

If you like this program you could (if you want to) let me know by
sending me a postcard. 

Send it to:
Stefan Hellkvist
Tistelv. 6
S-193 34 SIGTUNA
SWEDEN


Best wishes

Stefan