Re: [emacs-bidi] mirroring of glyphs

[Alex Schroeder]

"Eli Zaretskii" <address@hidden> writes:

> It's very hard to look at this without a few debugging aids.  One such
> tool that helps a lot is to print the input string with final resolved
> levels under every character.  Could you add such a feature and post
> the results with the problematic strings?

Sure.  Perhaps it makes sense to read this mail using
outline-minor-mode.  :)

* Problem:

(bidi-visual-to-logical "<123H/>shalom<123H>" 'R2L)
returns    "<Hshalom<123</H123>"
instead of "<H123>shalom</H123>"

(bidi-pretty-print "<123H/>shalom<123H>")
"   <   1   2   3   H   /   >   s   h   a   l   o   m   <   1   2   3   H   >"

The R2L context means that the paragraph embedding level is set to 1.

In the end, this is what will be evaluated:

  (bidi-reorder-string
   str
   (bidi-resolve-implicit-levels
    (bidi-resolve-weak-types (bidi-get-types str) (oddp paragraph-level))
    (make-list (length str) paragraph-level))))

Here's some debugging info.  I always put the piece of code I used
followed by the output generated.  Below this output, I list
information from further up such as to keep the info together.
Example:

  CODE1
  RESULT1

  CODE2
  RESULT2 (output generated)
  RESULT1 (information from furhter up)

** bidi-get-types

(bidi-pretty-print 
 (bidi-get-mnemonics
  (bidi-get-types "<123H/>shalom<123H>")))
"  ON  EN  EN  EN   R  ES  ON   L   L   L   L   L   L  ON  EN  EN  EN   R  ON"
"   <   1   2   3   H   /   >   s   h   a   l   o   m   <   1   2   3   H   >"

** bidi-resolve-weak-types

(bidi-pretty-print 
 (bidi-get-mnemonics
  (bidi-resolve-weak-types
   (bidi-get-types "<123H/>shalom<123H>") t)))
"   R  EN  EN  EN   R   R   R   L   L   L   L   L   L   L   L   L   L   R   R"
"  ON  EN  EN  EN   R  ES  ON   L   L   L   L   L   L  ON  EN  EN  EN   R  ON"
"   <   1   2   3   H   /   >   s   h   a   l   o   m   <   1   2   3   H   >"

** bidi-resolve-implicit-levels

(let ((str "<123H/>shalom<123H>"))
 (bidi-pretty-print 
  (bidi-resolve-implicit-levels
   (bidi-resolve-weak-types (bidi-get-types str) t)
   (make-list (length str) 1))))
"   1   2   2   2   1   1   1   2   2   2   2   2   2   2   2   2   2   1   1"
"   R  EN  EN  EN   R   R   R   L   L   L   L   L   L   L   L   L   L   R   R"
"  ON  EN  EN  EN   R  ES  ON   L   L   L   L   L   L  ON  EN  EN  EN   R  ON"
"   <   1   2   3   H   /   >   s   h   a   l   o   m   <   1   2   3   H   >"

* Possible fix: string-reverse

When reversing input and output:

(string-reverse
 (bidi-visual-to-logical
  (string-reverse "<123H/>shalom<123H>") 'R2L))
returns "<H123>shalom</H123>" as required

This solves the immediate problem, but fails with the following:

(string-reverse
 (bidi-visual-to-logical
  (string-reverse "<h123>MALAAS</h123>") 'L2R))
return     "<hSAALAM<123</h123>"
instead of "<h123>SAALAM</h123>"

(bidi-pretty-print "<h123>MALAAS</h123>")
"   <   h   1   2   3   >   M   A   L   A   A   S   <   /   h   1   2   3   >"

** bidi-get-types

(bidi-pretty-print 
 (bidi-get-mnemonics
  (bidi-get-types "<h123>MALAAS</h123>")))
"  ON   L  EN  EN  EN  ON   R   R   R   R   R   R  ON  ES   L  EN  EN  EN  ON"
"   <   h   1   2   3   >   M   A   L   A   A   S   <   /   h   1   2   3   >"

** bidi-resolve-weak-types

This is without reversing the string:

(bidi-pretty-print 
 (bidi-get-mnemonics
  (bidi-resolve-weak-types
   (bidi-get-types "<h123>MALAAS</h123>"))))
"   L   L   L   L   L   L   R   R   R   R   R   R   L   L   L   L   L   L   L"

Here the reversed string is passed to the bidi functions:

(bidi-pretty-print 
 (nreverse
  (bidi-get-mnemonics
   (bidi-resolve-weak-types
    (bidi-get-types
     (string-reverse "<h123>MALAAS</h123>"))))))
"   L   L  EN  EN  EN   R   R   R   R   R   R   R   L   L   L   L   L   L   L"
"  ON   L  EN  EN  EN  ON   R   R   R   R   R   R  ON  ES   L  EN  EN  EN  ON"
"   <   h   1   2   3   >   M   A   L   A   A   S   <   /   h   1   2   3   >"

** bidi-resolve-implicit-levels

(let ((str (string-reverse "<h123>MALAAS</h123>")))
 (bidi-pretty-print 
  (nreverse
   (bidi-resolve-implicit-levels
    (bidi-resolve-weak-types
     (bidi-get-types str))
    (make-list (length str) 1)))))
"   2   2   2   2   2   1   1   1   1   1   1   1   2   2   2   2   2   2   2"
"   L   L  EN  EN  EN   R   R   R   R   R   R   R   L   L   L   L   L   L   L"
"  ON   L  EN  EN  EN  ON   R   R   R   R   R   R  ON  ES   L  EN  EN  EN  ON"
"   <   h   1   2   3   >   M   A   L   A   A   S   <   /   h   1   2   3   >"

Alex.
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