[Freebangfont-devel] [Bug 118301] New - ba + <halant> applied to wrong character

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http://bugzilla.gnome.org/show_bug.cgi?id=118301

Changed by address@hidden

--- shadow/118301       Fri Jul 25 10:29:01 2003
+++ shadow/118301.tmp.19506     Fri Jul 25 10:29:01 2003
@@ -0,0 +1,141 @@
+Bug#: 118301
+Product: pango
+Version: 1.2.x
+OS: Linux
+OS Details: 
+Status: NEW   
+Resolution: 
+Severity: normal
+Priority: Normal
+Component: general
+AssignedTo: address@hidden                            
+ReportedBy: address@hidden               
+TargetMilestone: ---
+URL: 
+Cc: address@hidden,address@hidden,address@hidden
+Summary: ba + <halant> applied to wrong character
+
+Trying to keep track of the four different issues in 
+bug 113551 was pretty much impossible for me, so splitting
+up the comments into separate bug reports.
+
+* address@hidden (Sayamindu Dasgupta):
+
+2. Baphala
+---------------
+
+Pango, for some reasons is confusing between the sequence 09AC 09CD. This
+sequence can be substituted by two different lookups  - pres, and blws.
+Examples are given below.
+
+pres - &#2460;&#2476;&#2509;&#2470; 
+blws - &#2460;&#2509;&#2476;&#2470; 
+
+[ See:
+
+http://www.nongnu.org/freebangfont/pango_bugs/shot_bugs_gedit.jpg 
+http://www.nongnu.org/freebangfont/pango_bugs/shot_bugs_yudit.jpg
+
+for screenshots  - OT ]
+
+I have attached a screenshot of how the above two examples look in Yudit.
+More details on blws can be found at
+http://www.microsoft.com/typography/otfntdev/bengalot/features.htm
+(section on Below-base substitutions)
+
+* Additional Comments From Taneem Ahmed 2003-06-01 01:05
+
+The second patch includes the previous fix for 1a, and fix for 2. 
+[ http://bugzilla.gnome.org/showattachment.cgi?attach_id=17022 ]
+
+* Additional Comments From Owen Taylor 2003-06-01 02:55
+
+Regarding 2. - it seems that your change disallows below-base-forms
+for all characters, which can't be right, can it?
+
+In a brief look, perhaps the problem is that "reph" is not
+being done for U+9AC, which I believe, as the Bengali Ra
+should be getting it?
+
+If I make the change of U+9AC from _cb (consonant with below-base,
+to _rb, consonant with below base and reph), I get the image
+that I've attached above. I have no idea if this is correct
+or not, though at least there are different results for the
+two sequences....
+
+(If this change is correct, then ICU needs it as well.)
+
+* Additional Comments From Taneem Ahmed 2003-06-01 03:13
+
+U+9AC should be _bb (right now in CVS it is _bb not _cb). Reph is only 
+for U+9B0. I am attaching two screenshots with _bb and _rb. As you can 
+see for _rb the result is the same, which is not correct. The result should 
+be as produced by _bb. 
+
+* Additional Comments From Owen Taylor 2003-06-01 04:04
+For 2, OK, my change wasn't right .... I really don't know
+anything about Bengali, as you can tell :-). So, do we
+have any idea *what* is going wrong? 
+
+The output of indic_ot_reorder, with the features *not*
+applied is:
+
+ U+99C U+9AC U+9CD U+9A6
+ dist  dist  dist  dist
+ rphf  rphf  rphf  rphf
+ bwlf              bwlf
+ half              half
+ pstf              pstf
+
+
+Tracing through TT_GPOS_Apply_String, the features that
+take effect are first, the middle two characters are
+combined into a ra-below-base form by 'blwf', then
+second, 'blws' combines the first and second glyphs.
+
+Eric would have know better, but I'm wondering if the
+problem isn't simply that the features are supposed
+to be applied syllable by syllable and we're doing
+the whole string at once.
+
+* Additional Comments From Taneem Ahmed 2003-06-01 04:54
+
+For 2, the problem is with the tags. Consider the following two inputs: 
+U+99C U+9AC U+9CD U+9A6 
+U+99C U+9CD U+9AC U+9A6 
+ 
+After reorder, both should be (and is): 
+U+99C U+9AC U+9CD U+9A6 
+ 
+The difference is in the tags. For the first case, we should have blwf_p 
+for U+9AC U+9CD. With out the patch I proposed, pango sets blwf_p by 
+default to everything, as result to the second case too. 
+
+* Additional Comments From Owen Taylor 2003-06-01 10:49
+
+About 2, one concern would be a case where you have 
+a subscript form beneath a dead consonant 
+(C + virama + C_below + virama + C)
+or devanagari ra, this is described in R8 of the
+Unicode book's Devanagari section (Chapter is available
+for download from 
+http://www.unicode.org/versions/Unicode4.0.0/.)
+
+R8 is specifically mentioned as applying to other subscript
+consonants for Gurmukhi in the Unicode chapter as well.
+
+So, you only want to supress blwf on the *first* 
+consonant of the syllable, not on all pre-base consonants.
+
+So, something as simple as:
+
+ gulong tag = (i == baseLimit) ? half_p : blwf_p
+
+may be right, but I'd really like to get Eric Mader to 
+look at this before we change things, since this affects
+all Indic scripts.
+
+* Additional Comments From Taneem Ahmed 2003-06-01 16:50
+
+And your suggestion "gulong tag = (i == baseLimit) ? half_p : blwf_p" 
+does work.