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Browse Prior Art Database

Font Width Tables Used to Process Typographic Proportional Fonts

IP.com Disclosure Number: IPCOM000122413D
Original Publication Date: 1991-Dec-01
Included in the Prior Art Database: 2005-Apr-04
Document File: 4 page(s) / 175K

Publishing Venue

IBM

Related People

Carter, KE: AUTHOR [+2]

Abstract

To support typographic fonts, DisplayWrite* 5/2 (DW5/2) required a method to determine the metrics of the font to calculate line endings.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 37% of the total text.

Font Width Tables Used to Process Typographic Proportional Fonts

      To support typographic fonts, DisplayWrite* 5/2 (DW5/2)
required a method to determine the metrics of the font to calculate
line endings.

      A word processor, such as DisplayWrite 5/2, must understand the
escapement value for each character and symbol in a font to correctly
determine how many characters and symbols fit between a left and
right margin.  An escapement value defines how much horizontal space
a character or symbol requires.

      Previously, DisplayWrite Personal Computer products only
supported fixed pitch printer fonts and predefined proportional (PSM)
fonts.  For fixed pitch fonts, all characters and symbols have the
same escapement value which is defined by the pitch.  The characters
and symbols in the predefined proportional fonts do not all have the
same escapements.  However these fonts are specifically defined for
IBM printers, so IBM explicitly defines an escapement value for each
character and symbol in the font.  Therefore, when a user selects a
PSM font, DW PC understands the escapement values based on the IBM
standard definition.  For both fixed pitch and predefined PSM fonts,
previous DW PC products could easily understand the font escapement
values and correctly determine how many characters and symbols to
position on a line.

      For DW5/2, a requirement was made to support typographic
proportional fonts on OEM printers.  These fonts are defined by the
OEM printer manufacturers and third-party vendors.  Since no single
company controls the definition of these fonts across all printer
manufacturers and font producers, an application cannot assume a
standard set of escapement values when processing text for printer
fonts selected by the user.  Furthermore, with the multitude of
existing printer fonts and the continual distribution of new fonts,
an application must be able to quickly support a wide variety of
fonts (and the corresponding escapement values) to remain
competitive.  In addition, the solution identified must handle a
variety of different types of printer fonts including:
      - Internal Printer Fonts (fonts internal to the printer)
      - External Printer Fonts (font elements, cartridges, etc.)
      - Soft Fonts (fonts downloaded into the printer)
      - APA Fonts (fonts whose characters are bit mapped)
      - Postscript Fonts (fonts whose characters are defined by
outline technology)

      To maintain compatibility, DW5/2 must be able to interchange
Revisable Form Text (RFT) documents among other IBM (and OEM)
products.  This IBM strategy allows a user to transfer documents
among multiple products for consistent processing across all
environments.  However, this requires DW5/2 to store and process text
using EBCDIC code pages rather than the ASCII code pages supported by
the PC printers and fonts.  Therefore, DW5/2 must associate an ASCII
character escapement in...