Rounding measurement factors

TROUBLESHOOTING

Laser printing systems use only dot units when actually compiling forms. Therefore, as long as all positioning commands within FDL are defined in terms of dots or an integral number of dots, there are no rounding problems.

Converting other unit values to dots

You can define positions in decimal-value inches, in centimeters, in lines per inch, and in characters per inch. The LPS converts all of these commands to dots while the form is being compiled.

Many of the possible defined values (lines per inch, centimeters, and so forth) cannot be reduced to an integral number of dots. For example, if a coordinate system uses 13.6 characters per inch (cpi), that number may be translated to approximately 22.058823 dots per character unit. The compiler rounds the converted number to the nearest whole dot before starting to compile the form.

Example The following example illustrates the problems encountered using the 13.6 cpi coordinate system:

AT 4 DRAW 1 HOR LINE FROM -1 TO 132 USING SOLID 1;

AT 5 DRAW 1 HOR LINE FROM -1 TO 132 USING SOLID

HAIRLINE;

AT 8 DRAW 15 VER LINES FROM 4 TO 5 USING HAIRLINE

AND REPEAT HOR EVERY 8;

In theory, this form description technique creates 14 boxes that can be found simply by addressing the appropriate coordinates. In fact, the coordinates of the boxes are not exactly those expected. The boxes can be found by using the IN NEXT BOX parameter of the TEXT IN BOX command.

The IN NEXT BOX parameter works properly because it specifies the next adjacent box, but does not specify the coordinates of that box. The problem in addressing coordinates is that the FDL statement requires vertical lines every 176.47058 dots, which is rounded down by the system to 176.00000 dots.

This difference makes it impossible for the LPS to find box 14 at the coordinates 4, 112. There are two ways to draw the form to overcome this problem. One way is to draw 13 lines with the REPEAT parameter and then specify lines at 112 and 120. Another way is to change the final statement in the following manner:

AT 8 DRAW VER LINE FROM 4 TO 5 USING HAIRLINE AND

AT 16, 24, 32, 42, 48, 56, 72, 80, 88, 96, 104, 112, 120;

Unless a form is described with a coordinate system of only dots or an integral number of dots, the REPEAT parameter cannot be used to draw boxes that must be referenced by their coordinates.

4-14	XEROX 4050/4090/4450/4650 LPS FORMS CREATION GUIDE