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Mechanisms for Finding Substitute Fonts in a Conference-Enabled X Windows Application

IP.com Disclosure Number: IPCOM000122811D
Original Publication Date: 1998-Jan-01
Included in the Prior Art Database: 2005-Apr-04
Document File: 6 page(s) / 262K

Publishing Venue

IBM

Related People

Freer, JD: AUTHOR

Abstract

X Windows provides distributed client/server support for two-dimensional graphics support. An X application connects to the X server and communicates with it using X protocol, and asks the X server to create resources such as X windows on the server. In addition, the X server has resources that it has defined which may be used by any application that is connected to that server. X App | X Server | Display

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Mechanisms for Finding Substitute Fonts in a Conference-Enabled X
Windows Application

      X Windows provides distributed client/server support for
two-dimensional graphics support.  An X application connects to the X
server and communicates with it using X protocol, and asks the X
server to create resources such as X windows on the server.  In
addition, the X server has resources that it has defined which may be
used by any application that is connected to that server.
                               X App
                                 |
                              X Server
                                 |
                              Display

      One of these resources is X fonts.  Applications use X fonts
primarily to display text on workstation windows.  A font in X is a
set of bitmaps or outlines representing text, cursor shapes, or some
other application defined shapes.

      Before an application may use a font, it must request the X
server to "load" or "open" the font.  (The X protocol for this
request is called OpenFont but application programmers make a call to
XLoadFont.  In this disclosure, we will use the term "load" font to
describe this procedure).  If the X server cannot find the font in
its font path or if there is an error with the font file, the X
server will return an X error to the application.  When this occurs,
most applications request the X server to load an alternate font.
The significance of this is that applications are expected to use
fonts that  are generally available, and that X servers have no
responsibility to substitute a font if one is not available.

      When an X application is conference-enabled, the application
connects to an X Window conference-enabler rather than the X Server.
An X Window conferencing enabler appears to the application to be an
X server, while at the same time appearing to the X server as an
application, as shown below.
                              X App
                                |
                      X Conferencing Enabler
                                |
                             X Server
                                |
                             Display

      The X Windows conference-enabler connects to multiple X servers
on behalf of the application, displaying the application on each
display.  The application is not aware that it is being displayed on
multiple X servers.
                              X App
                                |
                      X Conferencing Enabler
      ...