RomWBW/Source/Images/d_zsdos/u1/ZDEPROP.DOC

ZDEPROP.DOC
Proportional Spacing with ZDE
June 2, 1990
Carson Wilson

          1.  INTRODUCTION.
          2.  USING ZDE'S PROPORTIONAL FORMATTING FEATURE
          3.  INSTALLATION AND CUSTOMIZATION.


1.  INTRODUCTION.

ZDE version 1.6 incorporates an elemental proportional formatting 
feature.  This option is useful only to those whose printers have 
proportional spacing capabilities.  Proportional formatting allows 
you to format ragged right text properly for proportional output. 
Centering and right justification of proportional text are not 
available.


2.  USING ZDE'S PROPORTIONAL FORMATTING FEATURE

Proportionally spaced printing gives a more professional look, 
allowing more characters to be printed on a line without 
crowding.  This is because less space is allocated to narrow 
characters like "i" and more to wide characters like "M."  Most 
computer printers do NOT allow proportional spacing; only laser 
printers, some daisy-wheel equipment, and newer dot-matrix 
printers have this ability.  Typically, there is a special set of 
instructions which when sent to the printer, cause it to use 
proportional spacing rather than monospacing.  On some models 
(the Silver Reed SR550 for example), DIP switches also control 
this feature.

ZDE does not itself perform proportional spaced printing; it 
simply allows you to format your text for use with a printer that 
has this capability.  You must instruct your printer to space 
proportionally before sending text to it.  If you have tried using 
the proportional capability of your printer, you probably have 
noticed that LINES WITH LOTS OF WIDE CHARACTERS IN THEM 
print out much wider than lines comprised of narrow characters.  
ZDE 1.6 allows you to compensate for this by counting the width 
of each character when it formats a paragraph (^B command), and 
wrapping each line when its width count reaches the equivalent 
of the current right margin setting.

The ^OJ command toggles this feature on and off [the default may 
also be installed with ZDENSTAL].  When proportional spacing is 
active, the legend "PS" appears in ZDE's status line (this is 
overwritten by "MR" when the margins are released).  
Proportional spacing occurs only during the ^B reformat command, 
not during wordwrap, so to format a document proportionally, you 
must use ^B at the beginning of each paragraph after you key it 
in.  Still, the results are well worth the extra trouble, especially 
for material that will be reproduced.


3.  INSTALLATION AND CUSTOMIZATION.

ZDE comes preconfigured to format text for proportional spacing 
with Epson's new LQ510 dot matrix printer.  Since most printers 
allocate roughly the same ratios of space to the various 
characters, there is a good chance you won't need to install ZDE 
for your printer.  This file has been formatted for proportional 
output by ZDE; try printing it proportionally to see the results.

If you should decide to change ZDE's proportional spacing to 
match your printer, you can patch ZDE's offset values for 
individual characters.  The offsets are stored in a sequential 
ASCII table whose location is given by ZDENSTAL's "F" option.  
The table consists of positive and negative (2's compliment) byte 
values, one for each character beginning with " " and going 
through "~".  As distributed, all of the values are either -12, -6, 
0, +6, or +12.  The negative numbers are expressed as (256+n), 
where n is the negative number.  So for example, -6 is expressed 
as (256+(-6)) or 250 (FA hex).

ZDE uses its ASCII table as follows.  When reformatting a line, 
ZDE counts each character as (30+table value)/30 of a column 
wide.  So if the offset is zero, the character is one column wide 
(30/30 = 1) and ZDE increments the current column by one.  If 
the character's offset is -6, it counts as only (30+(-6)/30) or 
24/30 columns wide, and ZDE increments the current column by 
only 24/30.  If the character's offset is +12, it counts as 42/30 
columns wide, and so on.  When a full column is "lost" due to 
characters with negative offsets, ZDE adds the next character to 
the line without incrementing the column count.  Similarly, when 
enough "extra" columns are counted to equal a full character, ZDE 
increments its column count without actually adding another 
character to the line.

To see the effects of this, try reformatting a paragraph or two, 
first with PS on, then with it off.  Lines of wide characters are 
shortened on screen, while lines of narrow characters are allowed 
to extend beyond the right margin.  When the text is printed 
proportionally, your printer reverses the process.  Lines of wide 
characters are lengthened and lines of narrow characters are 
shortened, the net result being proportionally spaced text with an 
even right margin.

If your printer's proportional output is not properly compensated 
for by ZDE, it is possible to install another offset table within 
ZDE to suit your needs.  The current table's address is given by 
ZDENSTAL's "F" option.  To find the location of a character's 
offset, add its ASCII value to ZDE's table address and subtract 
32.  For example, the ASCII value for "A" is 65, so the location of 
"A"'s offset is (table address+65-32) or (table address+33).

You may adjust a character's offset to any value between -34 and 
+35 decimal, but keep in mind that offsets if less than -29 may 
result in lines that _never_ reformat since characters with 
offsets of -30 or less take up no virtual space or less!  To 
calculate the proportional ratios used by your printer, it is best 
to print out a line of thirty of each character in proportional 
mode and compare the length of each line to the others.  Most 
characters should result in lines of roughly the same length; this 
is your "base" length, and you should set the offsets of these 
characters in ZDE to 00.  Other lines will probably fall into four 
or so other lengths; hopefully these lengths will correspond to an 
even xx/30ths of the "base" length.  To get the proper offset 
value, just subtract the number of characters equal in length to 
a line of "base" characters from 30.  For example, if only 18 
capital "M"'s take up the same length as 30 base characters, the 
offset for "M" is 30-18 or +12.  If it takes 42 "i"'s to equal the 
length of 30 base characters, the offset for "i" is 30-42 or -12.

Once you have determined the offsets in 30ths of each 
character's width from the base length, just plug these values 
into ZDE's proportional table.  You can use a patcher to alter a 
few characters.  For extensive modification, I have provided the 
assembly language file ZDEPROP.Z80 which can be assembled to a 
.HEX file overlay file for ZDE.  Before assembling ZDEPROP.HEX, 
you must edit the file and set the equate TABLE to the current 
address of ZDE's proportional spacing table as given by 
ZDENSTAL.  Then overlay ZDE with ZDEPROP.HEX using MLOAD, 
SID, or DDT.

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