204084 - Fix Tamil unicode rendering with **opentype** layout tables

Status: RESOLVED INCOMPLETE

(Core :: Layout: Text and Fonts, defect)

Description

[Manmathan Kumarathurai]

User-Agent:       Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.3) Gecko/20030312
Build Identifier: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.3) Gecko/20030312

Like bug 140013 but for Linux. (It seems that bug 140013 is invalid.)


Reproducible: Always

Steps to Reproduce:
1.
2.
3.

Comment 1

[Prabhat Hegde]

To re-iterate what Jungshik said in (id=140013), if you require complete Tamil
support there are 2 options. 1- support OT or 2 - use the short-term converter
approach similar to Thai (tis620* or hindi (sun.unicode.india-0) approach). If
someone could volunteer to produce a shaper similar to pango shapers would be
happy to QA and integrate it. Until then it will remain as "future". If partial
(just rendering) support is needed, Jungshik's patch (id=122195) will help.

Comment 2

[Jungshik Shin]

> Like bug 140013 but for Linux.

I've already filed bug 204039 as you know. If you want this bug to specifically
deal with Tamil
rendering with **opentype** layout tables, I think it's better to
make that clear in the summary line.

As  Prabhat wrote, just for rendering (within the limitation of TSCII fonts), my
patch
uploaded to bug 204039 would do it.

Prabhat, it seems like we have to find a way to invoke (as opposed to 
rolling out our own PangoLite in Mozilla) Pango APIs from nsFontMetricsXft.cpp (and
other places for editing/selectin/cursor....)  
Actually, the whole nsIFontMetrics interface can be written in terms of Pango APIs
(or Uniscribe APIs for nsFontMetricsWin and selection/editing in Mozilla-Windows).
It appeared that blizzard (see my and his comments in bug 176290) considered
that approach
but dropped it because Owen told him that Pango was rather slow. Nonetheless, he
agrees that
Pango is for complex scripts. If we can figure out a simple way to bridge Mozilla's 
nsFontMetricsXft (and other places for editing/cursor movement/selection, and so
forth) and Pango
(as installed as a system component) without going all the way to 'Pangozing'
nsFontMetricsXft 
(i.e.use Xft APIs for 'simple' scripts while invoking Pango APIs for complex
scripts)
it  would be a great boon for complex scripts. 
SILA project at <http://sila.mozdev.org> may shed some light on this. 
What would you say? 

Comment 3

[Manmathan Kumarathurai]

I would like the long term solution, i.e. use opentype tables.

How can I help? I do not know anything about opentype tables, cmaps, but if you
give me some pointers, maybe I can help.

Comment 4

[Manmathan Kumarathurai]

Attachment: Incorrect reordering/combining of tamil unicode.

Mozilla(Linux) displaying the below text using the Code2000 font. (As requested
by Mr. Srivas).

திருவள்ளுவர்

அல்லது
வாழ்க்கை
விளக்கம்

அறத்துப்பால்

ஆயிரக்கணக்கான

கிளைகளையும்
விழுதுகளையும்

உடைய ஆல்
முதலிய
மரங்களைவிட,
நுட்பமான
உறுப்புகளை
உடையவனாய்
நூறாயிரக்கணக்காகத்
தம் இனத்தைப்
பெருக்க
வல்லனவாய்
உள்ள
சிற்றுயிர்களைவிட,

இரவும்
பகலும் ஓயாது
உழைக்கவல்ல
எறும்பு
முதலியவற்றைவிட,
எங்கும்

Comment 5

[Manmathan Kumarathurai]

Attachment: Same text using the TSCu_Paranar.ttf font

Comment 6

[Gabriel Sjoberg]

Please recheck this bug against a recent nightly build[1] to verify that the
behavior still exists and post the results here.

Thanks.

[1] ftp://ftp.mozilla.org/pub/mozilla.org/firefox/nightly/latest-mozilla1.8/

Comment 7

[Tony Mechelynck [:tonymec]]

No reply to comment #6 since 2005-09-06 => INCOMPLETE.

Reopen if you can reproduce this bug on a recent build (and say which build).