Bi-directional display

• US 9,146,619 B2
• Filed: 08/08/2006
• Issued: 09/29/2015
• Est. Priority Date: 04/19/2001
• Status: Expired due to Fees

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Atkin, Steven Edward
• Primary Examiner(s): HUYNH, THU V
• Application Number:
  US11/463,131
• Publication Number:
  US 20070008331A1
• Time in Patent Office: 3,339 Days
• Field of Search: 715255-256, 704/8, 717/117
• US Class Current: 1/1
• CPC Class Codes: G06F 3/018 Input/output arrangements for oriental characters
• CPC Class Codes: G06F 3/0489 using dedicated keyboard keys or combinations thereof
• CPC Class Codes: G06F 40/10 Text processing natural language analysis G06F40/20; semantic analysis G06F40/30; processing or translation of natural language G06F40/40
• CPC Class Codes: G06F 40/129 Handling non-Latin characters, e.g. kana-to-kanji conversion

Abstract

A bidirectional text display method embodied in a functional programming language which first assigns bidirectional attributes to a logical character stream. Next, through explicit processing, level numbers are assigned, honoring any directional overrides present in the logical character stream. Subsequent weak and neutral type processing potentially causes attribute types to change based upon surrounding attribute types. Then, implicit processing assigns final level numbers to the stream which control reordering. Finally, reordering processing produces a sequence of characters in display order. By separating the facets of layout dealing with reordering from those that are concerned with rendering, such as line breaking, glyph selection, and shaping, the Haskell-based method is more discernible and comprehendable, thereby allowing it to be more useful as a model upon which others may base bidirectional implementations.

Claims

1. A computer-implemented method for displaying bi-directional text on a computer display comprising:

detecting by a computer that a string of characters for display to a human interface device contains one or more Arabic Letters followed by one or more European Numbers;

responsive to the detecting, treating by the computer the one or more European Numbers as one or more Arabic Numbers by;

assigning bidirectional attributes to a logical character stream;

assigning initial level numbers while honoring any directional overrides by explicit processing, wherein the directional overrides include Left-to-right display order and Right-to-left display order;

changing attribute types based upon surrounding attribute types through weak processing and neutral processing, wherein, during the weak processing, a directional override is changed to Right-to-left display order for a last Arabic Letter of the one or more Arabic Letters which immediate precedes a first character of the one or more European Numbers while retaining an attribute type of Arabic Letter for the last Arabic Letter, thereby causing the first European Number to change to an attribute type of Arabic Number;

associating final level numbers to the logical character stream through implicit processing; and

reordering the string of characters within the logical character stream into display order according to the final level numbers by separately handling facets of layout relating to character reordering and facets related to character stream rendering; and

displaying by a computer the reordered string of characters to a human interface device.

2. The computer-implemented method as set forth in claim 1 wherein the reordering is performed in at least in part in a functional programming language.

3. The computer-implemented method as set forth in claim 1 further comprising handling the character stream as sequential runs of integers during the steps of assigning attributes, level numbers, changing attribute types, associating final level numbers, and reordering characters.

4. The computer-implemented method as set forth in claim 1 wherein the step of changing attribute types based upon surrounding attribute types through weak and neutral processing in a functional programming language comprises providing blocks of functional programming language indexed by name weak type processing, neutral type processing, and implicit level processing such that the method may be readily used as a reference.

5. The computer-implemented method as set forth in claim 1 wherein one or more steps are provided at least in part in Haskell functional language.

6. The computer-implemented as set forth in claim 1 wherein one or more steps are provided at least in part in Erlang functional language.

7. The computer-implemented method as set forth in claim 1 wherein one or more steps are provided at least in part in Standard Machine Language (“

SML”

) functional language.

8. The computer-implemented method as set forth in claim 1 wherein one or more steps are provided in Miranda functional language.

9. The computer-implemented method as set forth in claim 1 wherein one or more steps are provided at least in part in Lisp functional language.

10. The computer-implemented method as set forth in claim 1 wherein one or more steps are provided at least in part in Scheme functional language.

11. A computer program product for displaying bi-directional text on a computer display comprising:

a computer-readable storage memory device suitable for storage of program instructions;

program instruction embodied by the computer-readable storage memory device which cause a computer processor, when executed, to;

detect a string of characters for display to a human interface device contains one or more Arabic Letters followed by one or more European Numbers;

assign bidirectional attributes to a logical character stream;

assign initial level numbers while honoring any directional overrides by explicit processing, wherein the directional overrides include Left-to-right display order and Right-to-left display order;

change attribute types based upon surrounding attribute types through weak processing and neutral processing, wherein, during the weak processing, a directional override is changed to Right-to-left display order for a last Arabic Letter of the one or more Arabic Letters which immediate precedes a first character of the one or more European Numbers while retaining an attribute type of Arabic Letter for the last Arabic Letter, thereby causing the first European Number to change to an attribute type of Arabic Number;

associate final level numbers to the logical character stream through implicit processing; and

reorder the string of characters within the logical character stream into display order according to the final level numbers by separately handling facets of layout relating to character reordering and facets related to character stream rendering; and

display the reordered string of characters to a human interface device.

12. The computer program product as set forth in claim 11 wherein the program instruction for reordering comprises functional programming language.

13. The computer program product as set forth in claim 11 further comprising program instruction to handle the character stream as sequential runs of integers during the steps of assigning attributes, level numbers, changing attribute types, associating final level numbers, and reordering characters.

14. The computer program product as set forth in claim 11 wherein the program instruction for changing attribute types based upon surrounding attribute types through weak and neutral processing comprises blocks of functional programming language indexed by name weak type processing, neutral type processing, and implicit level processing such that the method may be readily used as a reference.

15. The computer program product as set forth in claim 11 wherein the program instruction comprises Haskell functional language.

16. The computer program product as set forth in claim 11 wherein the program instruction comprises Erlang functional language.

17. The computer program product as set forth in claim 11 wherein the program instruction comprises Standard Machine Language (“

SML”

) functional language.

18. The computer program product as set forth in claim 11 wherein the program instruction comprises Miranda functional language.

19. The computer program product as set forth in claim 11 wherein the program instruction comprises Lisp functional language.

20. The computer program product as set forth in claim 11 wherein the program instruction comprises Scheme functional language.

21. A text code conversion system for displaying bi-directional text on a computer display comprising:

a computer processor for performing a logical process;

a computer-readable storage memory device suitable for storage of program instructions;

program instruction embodied by the computer-readable storage memory device which cause a computer processor, when executed, to;

detect a string of characters for display to a human interface device contains one or more Arabic Letters followed by one or more European Numbers;

assign bidirectional attributes to a logical character stream;

assign initial level numbers while honoring any directional overrides by explicit processing, wherein the directional overrides include Left-to-right display order and Right-to-left display order;

change attribute types based upon surrounding attribute types through weak processing and neutral processing, wherein, during the weak processing, a directional override is changed to Right-to-left display order for a last Arabic Letter of the one or more Arabic Letters which immediate precedes a first character of the one or more European Numbers while retaining an attribute type of Arabic Letter for the last Arabic Letter, thereby causing the first European Number to change to an attribute type of Arabic Number;

associate final level numbers to the logical character stream through implicit processing; and

reorder the string of characters within the logical character stream into display order according to the final level numbers by separately handling facets of layout relating to character reordering and facets related to character stream rendering; and

display the reordered string of characters to a human interface device.

22. The text code conversion system as set forth in claim 21 wherein the assigning of bidirectional attributes comprises obtaining bidirectional attributes from a character database.

23. The text code conversion system as set forth in claim 21 wherein the program instruction further comprises program instructions for grouping characters into sequential runs using type constructors and level such that characters are processed collectively rather than individually.

24. The text code conversion system as set forth in claim 21 wherein the program instructions for changing attribute types comprises blocks of functional programming language indexed by name weak type processing, neutral type processing, and implicit level processing such that the method may be readily used as a reference.

25. The text code conversion system as set forth in claim 21 wherein the program instruction comprise Haskell functional language.

26. The text code conversion system as set forth in claim 21 wherein the program instruction comprise Erlang functional language.

27. The text code conversion system as set forth in claim 21 wherein the program instruction comprise Standard Machine Language (“

SML”

) functional language.

28. The text code conversion system as set forth in claim 21 wherein the program instruction comprise Miranda functional language.

29. The text code conversion system as set forth in claim 21 wherein the program instruction comprise Lisp functional language.

30. The text code conversion system as set forth in claim 21 wherein the program instruction comprise Scheme functional language.