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Method for Adapters and Applications to Share Font Memory

IP.com Disclosure Number: IPCOM000104878D
Original Publication Date: 1993-Jun-01
Included in the Prior Art Database: 2005-Mar-19
Document File: 2 page(s) / 68K

Publishing Venue

IBM

Related People

Anderson, GD: AUTHOR [+4]

Abstract

One of the functions of a graphics workstation is the display of character data. It is common to support multiple fonts of characters. In fact, it is necessary to support multiple fonts if the work station is to offer more than a single language interface. Thus, workstations must have access to various font sets and be able to switch between them.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

Method for Adapters and Applications to Share Font Memory

      One of the functions of a graphics workstation is the display
of character data.  It is common to support multiple fonts of
characters.  In fact, it is necessary to support multiple fonts if
the work station is to offer more than a single language interface.
Thus, workstations must have access to various font sets and be able
to switch between them.

      Currently, workstations communicate character data to a
graphics adapter via a set of pixels or a set of lines.

      An application usually represents characters as a string of
codes, character codes.  These character codes vary from language to
language.  The encoding of fonts (the character code for each glyph)
varies between font standards (e.g., ISO8850 or PC850).   Thus some
type of table is required to inform the graphics adapter as to which
set of lines or pixels it should display.

      The font table describing the characters to be displayed is
required by the application (font manager),  kernel and adapter.
Thus, if the font table is copied between application and kernel,
both disk space and time will be lost in keeping two identical
copies.  This is espe cially important when dealing with fonts that
contain a large number of glyphs or characters.

      The operating system's memory structure requires that a single
process own any specific piece of memory (for example, font data).
This is commonly the same process that creates the data area.  Note
that both the creator and the current owner are considered owners.

      In prior implementations of the graphics subsystem, the font
data area is created and owned by the font manager.  The operating
system also allows a sharing mechanism by which the owning process
can share its data with another process.  This sharing mechanism is
used to allow the user...