Re: [cp-patches] FYi: Implement (naive) Bidi.requiresBidi() workaround

[Mark Wielaard]

Hi,

On Sat, 2005-12-24 at 11:10 +0100, Mark Wielaard wrote:
> But you are right that we could/should probably add most things from the
> weak and neutral category, which we know won't "disrupt"
> left-to-rightness:
> 
> DIRECTIONALITY_EUROPEAN_NUMBER (EN)
> DIRECTIONALITY_EUROPEAN_NUMBER_SEPARATOR (ES)
> DIRECTIONALITY_EUROPEAN_NUMBER_TERMINATOR (ET)
> DIRECTIONALITY_ARABIC_NUMBER (AN)
> DIRECTIONALITY_COMMON_NUMBER_SEPARATOR (CS)
> DIRECTIONALITY_SEGMENT_SEPARATOR (S)
> DIRECTIONALITY_WHITESPACE (WS)
> 
> I am not sure we should test for the others. I have been conservative
> with the above list (just so I don't have to read the whole bidi
> algorithm description). The idea behind requiresBidi() is that it is a
> quick way to determine whether to do full bidirectional analysis or not
> (or actually if the whole paragraph text is written left-to-right). So
> false positives aren't really a problem. It just means that you have to
> follow the full algorithm to get the full answer.

This patch implements the above.

2005-12-31  Mark Wielaard  <address@hidden>

    * java/text/Bidi.java (requiresBidi): Also test against character
    types L, EN, ES, ET, AN, CS, S and WS.

Committed,

Mark

Index: java/text/Bidi.java
===================================================================
RCS file: /cvsroot/classpath/classpath/java/text/Bidi.java,v
retrieving revision 1.1
diff -u -r1.1 Bidi.java
--- java/text/Bidi.java 23 Dec 2005 18:27:21 -0000      1.1
+++ java/text/Bidi.java 31 Dec 2005 10:44:10 -0000
@@ -44,24 +44,32 @@
  * TODO/FIXME Only one method <code>requiresBidi</code> is implemented
  * for now by using <code>Character</code>. The full algorithm is <a
  * href="http://www.unicode.org/unicode/reports/tr9/";>Unicode Standard
- * Annex #9: The Bidirectional Algorithm</a>. A ful implementation is
+ * Annex #9: The Bidirectional Algorithm</a>. A full implementation is
  * <a href="http://fribidi.org/";>GNU FriBidi</a>.
  */
 public class Bidi
 {
   /**
    * Returns false if all characters in the text between start and end
-   * are all left-to-right text.  WARNING, this implementation is
-   * slow, it calls <code>Character.getDirectionality(char)</code> on
-   * all characters.
+   * are all left-to-right text. This implementation is just calls
+   * <code>Character.getDirectionality(char)</code> on all characters
+   * and makes sure all characters are either explicitly left-to-right
+   * or neutral in directionality (character types L, EN, ES, ET, AN,
+   * CS, S and WS).
    */
   public static boolean requiresBidi(char[] text, int start, int end)
   {
-    final int LEFT_TO_RIGHT = Character.DIRECTIONALITY_LEFT_TO_RIGHT;
     for (int i = start; i < end; i++)
       {
-       char c = text[i];
-       if (Character.getDirectionality(c) != LEFT_TO_RIGHT)
+       byte dir = Character.getDirectionality(text[i]);
+       if (dir != Character.DIRECTIONALITY_LEFT_TO_RIGHT
+           && dir != Character.DIRECTIONALITY_EUROPEAN_NUMBER
+           && dir != Character.DIRECTIONALITY_EUROPEAN_NUMBER_SEPARATOR
+           && dir != Character.DIRECTIONALITY_EUROPEAN_NUMBER_TERMINATOR
+           && dir != Character.DIRECTIONALITY_ARABIC_NUMBER
+           && dir != Character.DIRECTIONALITY_COMMON_NUMBER_SEPARATOR
+           && dir != Character.DIRECTIONALITY_SEGMENT_SEPARATOR
+           && dir != Character.DIRECTIONALITY_WHITESPACE)
          return true;
       }

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