Simtel MSDOS 1992 September/Simtel20_Sept92.cdr/msdos/ventura/vpapp_8.arc/VPAPP_8.TXT

Text File | 1989-11-17 | 13KB | 267 lines

@PARAFILTR ON =

@BANNER = Ventura Publisher<M^><190><D>

@APP NOTE = Application Note #8

@NAME = Subjects:    Screen font problems<R>
    Bad WYSIWYG<R>
    Display spacing problems

The goal that all professional publishing software tries to achieve
is to show an exact representation on the screen of what eventually
gets printed. However, despite all the features built into Ventura
Publisher, some of you have reported discrepancies between your computer
screen and what gets printed. This lack of WYSIWYG (What You See Is
What You Get) can usually be attributed to one or more of the following
causes:

@BULLET 1 = Screen aspect ratio doesn't match printer

@BULLET 1 = Screen fonts don't match printer fonts.

@BULLET 1 = Small number of pixels per character at small point sizes.

@BULLET 1 = Width table altered.

@BULLET 1 = New screen fonts have different resolution from existing
screen fonts.

@BULLET 1 = Helvetica or Times Roman fonts are missing.

@BULLET 1 = Multiple spaces

@BULLET 1 = Font changes within a line

@BULLET 1 = Tabs & returns shown

@BULLET 1 = Size not available

The purpose of this application note is to describe these causes in
more detail and to provide recommendations on how to minimize or eliminate
the problems associated with each of these causes. By following these
recommendations, you can be assured of an excellent display which
very closely matches the printed output.

@HEAD 1 = Aspect<R>
ratio

Any computer display provides a different aspect ratio (i.e., ratio
of height to width) than the final printed output. This difference
can cause imperfections in how the character is placed on the screen.
Some displays provide better aspect ratio than others. EGA and Hercules
displays do not provide 1:1 aspect ratios and therefore are inferior
to VGA displays which do. The only solution to this problem is to
purchase a better display.

@HEAD 1 = Screen fonts don't match printer

Ventura Publisher is furnished with Times Roman and Helvetica screen
fonts. However, to provide simple access to all the fonts which are
embedded in many PostScript printers, Ventura Publisher includes a
width table which contains the character information for all of these
additional fonts. To provide an approximation of what the page will
look like when these other fonts are chosen, Ventura Publisher automatically
chooses Helvetica or Times Roman font for the screen display and then
adjusts the position of the characters on the screen to compensate
for the differences between the actual font and the Helvetica or Times
Roman which is being used as a proxy. This results in characters with
too much or too little spacing between them (see Figure 2).

To solve this problem, you should purchase (or generate with Fontware)
screen fonts which match the fonts with which you plan to print. PostScript
screen fonts can be obtained from the Ventura Publisher User Group.
Close approximations to PostScript fonts can be obtained using the
fonts available from Bitstream for Fontware.

@HEAD 1 = Insufficient number of pixels

Most computer displays (e.g., a VGA display) are capable of producing
a resolution which is equivalent to about 72 dots per inch. At this
resolution, small characters (i.e., 12 points or less) are only 5
or 6 dots wide. Therefore, if a small character must be placed on
the screen at a position equal to 5<$E1/2> dots from the last character,
the screen only allows this character to be placed 5 dots or 6 dots
from the last character. This half pixel error represents an error
of more than 10% of the character's width. Because of how Ventura
Publisher rounds numbers, the error can actually approach 20%, and
with exceptionally small characters (such as 6 or 8 point), the percentage
error can be even greater.

This effect usually only becomes a problem when body text (or other
small point size text) is kerned, because in this case Ventura Publisher
tries to move adjacent characters by a small amount, but the lack
of placement precision just described results in the character being
moved way too far (see Figure 3). In many cases, the visual result
on the screen for small type sizes is very distracting. The solution
is to set the <B>On-Screen Kerning<D> feature in the Set Preferences
option (Options menu) to <B>18<D> or greater. This will stop Ventura
Publisher from trying to adjust small type sizes on the screen (the
printed copy is not affected). As a side benefit, if you have automatic
kerning turned on for Body Text, changing the on-screen kerning value
dramatically improves screen drawing speed. (<B>Automatic Pair Kerning<D>
is set in the Paragraph menu's <B>Paragraph Typography<D> option.)

@HEAD 1 = Width table altered

When you create a new width table, it is possible to create incorrect
widths. For instance, if you try to merge widths for LaserJet fonts
with a PostScript width table, Ventura Publisher will alert you to
the pending problem, but will allow you to proceed if you choose.
The resulting width table will almost certainly contain width information
which doesn't match the printer in use. This in turn may result in
an incorrect display and, unlike the other problems listed in this
application note, will also result in a printed page which looks bad.
The solution to this problem is to use a width table that has not
yet been merged with another width table.

By the way, Ventura Publisher lets you merge width tables for different
printers because often different font vendors place a slightly different
printer name in the printer width table (such as <B>HP LaserJet<D>
instead of <B>HP LJ+<D>) even though the fonts are designed for the
same printer. By letting you proceed with the merge, Ventura Publisher
lets you merge the font information even though the identifying names
do not precisely match.

@HEAD 1 = Wrong screen fonts

The fonts included with Ventura Publisher are CGA (640 x 200), EGA
(640 x 350), or VGA (640 x 480) resolution. The <B>VPPREP<D> installation
program automatically installs the correct screen fonts for the display
driver you choose. If you later create more screen fonts using Fontware
or add screen fonts provided by any one of many font vendors, if the
resolution of these screen fonts is different from those already installed,
you may find that the fonts appear to large or too small (see Figure
4). Ventura Publisher <MI>does<D> allow you to mix fonts of different
resolutions, but to avoid these kinds of problems, only use those
which have the same resolution of those already in use.

@HEAD 1 = Helvetica or Times screen fonts replaced.

Ventura Publisher is <MI>hard-wired<D> to expect both Helvetica and
Times Roman fonts. If you create a width table which contains neither
of these fonts, the results can be quite unpredictable. Usually the
screen magnification changes dramatically. Instead of seeing <$E1/3>
of the screen in normal view, you will suddenly see only <$E1/6> or
less. The solution is to merge the faulty width table with one which
contains either Helvetica or Times Roman, preferably both.

@HEAD 1 = Size not available

Ventura Publisher provides screen fonts in various discrete sizes
(6, 8, 9, 10, 11, 12, 14, 18, 24) and in normal weight. When you request
a size (e.g., 13 point) or weight (e.g, italic) for which no screen
font is available, Ventura Publisher creates one in real time by adding
or deleting pixels from the nearest available size (see Figure 5).
The algorithm used was optimized for speed, but the results are notably
poorer than what you obtain when displaying a font size for which
a screen font is available. The screen also draws more slowly. The
solution is to create a screen font for each size and weight using
Fontware, or else purchase these screen fonts from your favorite font
vendor.

Note that each screen font is stored in a separate file, so even if
you have the money to buy or (with Fontware) the time to generate
lots of screen fonts, you should do so judiciously or you will find
your hard disk suddenly has been eaten up by huge numbers of screen
font files.

Ventura Publisher can handle a maximum of about 700 screen font files
at once.

@HEAD 1 = Tabs & returns shown

One of the most common problems with the screen display not matching
the printed output is caused by using the <B>Show Tabs & Returns<D>
option. This option is available in the Options menu and represents
all hidden features (e.g., index points, references) and characters
(e.g., tabs, line breaks, returns) by some appropriate marker character.
Because these characters don't appear on the printed page, and because
each line of text still ends at the same position on the page, the
characters on the line must be crowded together to make room for all
the markers. The obvious solution to this problem is to temporarily
<B>Hide Tabs & Returns<D> (Options menu).

@HEAD 1 = Font changes within a line

While in the Text mode, you can select a range of text and then change
its font using the <B>Set Font<D> feature (available in the <B>Assignment
List<D> while in Text mode). In most situations, the resulting text
looks just fine on the screen. However, when some of the other problems
described in this application note are present, selecting a different
font can magnify the problem, especially if the new font is larger.
The solution to this problem varies, but usually involves solving
one of the other problems mentioned in this note.

@HEAD 1 = Multiple spaces

Ventura Publisher does not <169>like<170> more than one space between
words. This is due to the fact that extra spaces can cause major problems
when they get placed at the end of a line. For example, suppose a
line of text contains three spaces between a pair of words. Suppose
further that while formatting this line, the first of the two words
happens to fall at the end of a line. If Ventura Publisher didn't
do something clever, that line would appear to be justified incorrectly.
The solution to this problem is that when loading a text file, Ventura
Publisher converts multiple spaces to one space plus multiple <B>non-breaking<D>
spaces. A non-breaking space is treated the same as a normal space
(i.e., it can be compressed or expanded during justification), but
it always forces the adjacent characters or words to be pulled to
the next line. When the adjoining character is a space, the effect
is to pull the space to the next line. Since Ventura Publisher suppresses
all spaces at the beginning of a line (both regular as well as non-breaking),
the effect is to remove all excess spaces when they fall at the end
of the line. It is a good solution to a very real problem.

However, this whole process can cause Ventura Publisher to move letters
slightly to the left or right of their correct position within the
words adjacent to these extra spaces when those spaces do not fall
at the end of a line. The solution is to:

@BULLET 1 = Select the Text mode.

@BULLET 1 = Move the text cursor through the text in the area where
you observe the problem. Keep your eye on the <B>Current Selection
Box<D> in the lower left corner of the screen.

@BULLET 1 = When you see the words <B>NoBreak Space<D>, press the
<B>Del<D> key to delete the extra space.

This problem is most often noticed by PostScript users because the
screen fonts used in Ventura Publisher were derived from Bitstream
outline. These outlines do not match the set widths of Adobe's (i.e.,
PostScript's) typefaces. To solve the problem, puchase the matching
screen fonts from Adobe Systems.

You should note that, like the other problems mentioned in this note,
this one only affects the screen display. Therefore, you may choose
to ignore it since the printed page will look OK.

@HEAD 1 = Summary

The differences between a computer display and a piece of paper make
it impossible to achieve perfect WYSIWYG. However, you can achieve
excellent results for even the most critical applications if you do
the following:

@BULLET 1 = Set <B>On-Screen Kerning<D> (<B>Set Preferences<D> option
in the Options menu) to <B>18<D>. Unless you own a <MI>very<D> high
resolution display, you should never display kerning on the screen
for sizes under 18 points. As a side benefit, you will notice a marked
improvement in screen drawing performance <MI>if<D> you have kerning
turned on for the majority of text on a page.

@BULLET 1 = For every typeface, generate or purchase screen fonts
which match each size and weight you plan to use.

@BULLET 1 = Make sure the width table you use has not been merged
with a width table for another printer, and make sure Helvetica and
Times Roman (or Swiss and Dutch) are still contained in the Font list
in the Paragraph menu's <B>Font<D> option.

@BULLET 1 = Hide tabs & returns.

@BULLET 1 = Eliminate multiple spaces (created by pressing the space
bar) between words.