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Bidirectional Language Format Control

IP.com Disclosure Number: IPCOM000107969D
Original Publication Date: 1992-Apr-01
Included in the Prior Art Database: 2005-Mar-22
Document File: 5 page(s) / 197K

Publishing Venue

IBM

Related People

Gabbay, Y: AUTHOR [+5]

Abstract

Arabic and Hebrew are the primary languages of the Middle East. In both Arabic and Hebrew, words are written from right-to-left, but numbers and foreign languages such as English are written from left- to-right. This requires the ability to recognize and control changes in the direction in the flow of presentation.

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This is the abbreviated version, containing approximately 49% of the total text.

Bidirectional Language Format Control

       Arabic and Hebrew are the primary languages of the Middle
East. In both Arabic and Hebrew, words are written from
right-to-left, but numbers and foreign languages such as English are
written from left- to-right.  This requires the ability to recognize
and control changes in the direction in the flow of presentation.

      With unidirectional languages the Source Buffer can be the
Presentation Space.  This is not possible in the bidirectional mode
of operation because of factors such as orientation which affect the
Presentation Space appearance relative to the Source Buffer.

      Character sequence orientation in the Presentation Space may be
in either of two directions, i.e., left-to-right (LTR) or right-to-
left (RTL).  This bidirectional presentation may be an entire
Presentation space, a field within the Presentation Space, or
portions of a field referred to as segments.

      Thus, while all data in the Source Buffer is kept in a
monotonically increasing order, the order in the Presentation Space
may change when it is presented for viewing by the user.  The
Formatter provides the rules that are to be applied when displaying
the characters that are in the Source Buffer.  See Fig. 1.

      For Orientation, four levels of presentation are considered:
the physical screen, the partition presentation space, the field, and
the segment.  The sequence of formatting is to format fields and
segments into the Partition Presentation Space, and then apply the
Local Screen Reverse to achieve the resultant presentation.

      The orientation on the physical screen may be controlled by the
user via Local Screen Reverse.  Its function is to control whether
each row of data in the Presentation Space is displayed in the same
orientation as in the Presentation Space or reversed on the screen.

      The partition is the highest level which is controllable by
application programs.  The Partition Presentation Space orientation
is controlled by the Set Orientation attribute.  When set to LTR, the
Presentation Space is an image of the Source Buffer, i.e., as defined
for the generic screen.  When set to RTL, field positions within the
row are reversed relative to a generic orientation. Fig. 2
illustrates how the position reversal appears.  Not only are the
field positions reversed, but the field attribute position relative
to the field is changed from the left-hand side of the field to the
right- hand side.

      However, reversing the field position does NOT reverse the
direction of the data within the field.  The data direction is
controlled by the Extended Field Attribute type, Orientation.  Fig. 3
illustrates this data orientation relative to field sequencing.  A
field attribute number is used above the attribute to associate it
with the proper field (same number) in these examples.

      While the fields are reversed within the row, the row maintains
its r...