Attachment 82038 Details for Bug 66597 – More thorough description of the problem.

More thorough description of the problem.

Hindi-text-copy-PDF.txt (text/plain), 6.64 KB, created by Steve White on 2013-07-04 19:23:51 UTC

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Creator: Steve White

Created: 2013-07-04 19:23:51 UTC

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>Hi,
>
>LOWriter performs the best conversion of text to PDF, in the 
>sense of making the text copyable from the PDF file, of any 
>of the systems I've tried in Linux.
>
>In particular, in copying Hindi text, I know there are 
>a lot of hoops to jump, not the least being that the
>letters are often re-ordered by the font layout layer.
>
>However, in producing a PDF file containing Hindi text,
>there remain some problems.
> ----------------------------------------------------
>The tests I ran were the following.
>In a LOWriter doc, put several copies of the lines (Article 1 of the UDHR)
>à¤¸à¤à¥ à¤®à¤¨à¥à¤·à¥à¤¯à¥à¤ à¤à¥ à¤à¥à¤°à¤µ à¤à¤° à¤à¤§à¤¿à¤à¤¾à¤°à¥à¤ à¤à¥ à¤®à¤¾à¤®à¤²à¥ à¤®à¥à¤ à¤à¤¨à¥à¤®à¤à¤¾à¤¤ à¤¸à¥à¤µà¤¤à¤¨à¥à¤¤à¥à¤°à¤¤à¤¾ à¤à¤° à¤¸à¤®à¤¾à¤¨à¤¤à¤¾ à¤ªà¥à¤°à¤¾à¤ªà¥à¤¤ à¤¹à¥ à¥¤ 
>à¤à¤¨à¥à¤¹à¥à¤ à¤¬à¥à¤¦à¥à¤§à¤¿ à¤à¤° à¤à¤¨à¥à¤¤à¤°à¤¾à¤¤à¥à¤®à¤¾ à¤à¥ à¤¦à¥à¤¨ à¤ªà¥à¤°à¤¾à¤ªà¥à¤¤ à¤¹à¥ à¤à¤° à¤ªà¤°à¤¸à¥à¤ªà¤° à¤à¤¨à¥à¤¹à¥à¤ à¤à¤¾à¤à¤à¤¾à¤°à¥ à¤à¥ à¤à¤¾à¤µ à¤¸à¥ à¤¬à¤°à¥à¤¤à¤¾à¤µ à¤à¤°à¤¨à¤¾ à¤à¤¾à¤¹à¤¿à¤ à¥¤
>Format with a different font supporting Hindi.
>
>Next, "Export as PDF".
>Opened the resulting file with Adobe Reader.
>
>Now select and copy the text from the PDF file,
>and paste it into a text editor.
>(Oh, let's hope the system's default encoding is UTF-8!)
>
>It should appear like the original text above.
> ----------------------------------------------------
>Note that I've done analogous tests starting from Firefox
>(using the CUPS PDF printer), and with XeLaTex.
> ----------------------------------------------------
>xHere I compared the distro Lohit Hindi and Gargi, as well
>as GNU FreeSerif and GNU FreeSans (latest versions from SVN).
>This is LOWriter 4.0.2.2 on Ubuntu.
>
>Lohit Hindi
>à¤¸à¤à¥ à¤®à¤¨à¥à¤·à¥à¤¯à¥à¤ à¤à¥ à¤à¥à¤°à¤µ à¤à¤° à¤à¤§à¤¿à¤§à¤¿à¤à¤¾à¤°à¥à¤ à¤à¥ à¤®à¤¾à¤®à¤²à¥ à¤®à¥ à¤à¤¨à¥à¤®à¤à¤¾à¤¤ à¤¸à¥à¤µà¤¤à¤¨à¥à¤¤à¥à¤°à¤¤à¤¾ à¤à¤° à¤¸à¤®à¤¾à¤¨à¤¤à¤¾ à¤ªà¥à¤°à¤¾à¤ªà¥à¤¤ à¤¹à¥ à¥¤
>à¤à¤¨à¥à¤¹à¥ à¤¬à¥à¤¿ à¤à¤¦à¥à¤§à¤¿ à¤à¤° à¤à¤§à¤¨à¥à¤¤à¤°à¤¾à¤¤à¥à¤®à¤¾ à¤à¥ à¤¦à¥à¤¨ à¤ªà¥à¤°à¤¾à¤ªà¥à¤¤ à¤¹à¥ à¤à¤° à¤ªà¤°à¤¸à¥à¤ªà¤° à¤à¤¨à¥à¤¹à¥ à¤à¤¾à¤à¤à¤¾à¤°à¥ à¤à¥ à¤à¤¾à¤µ à¤¸à¥ à¤¬à¤¤à¤¾à¤°à¥à¤¤à¤¾à¤µ à¤à¤°à¤¨à¤¾ à¤à¤¾à¤¿ à¤à¤¹à¤ à¥¤
>FreeSerif
>à¤¸à¤à¥ à¤®à¤¨à¥à¤·à¥à¤¯à¥ à¤à¥ à¤à¥à¤°à¤µ à¤à¤° à¤à¤§à¤¿à¤§à¤¿à¤à¤¾à¤°à¥ à¤à¥ à¤®à¤¾à¤®à¤²à¥ à¤®à¥ à¤à¤¨à¥à¤®à¤à¤¾à¤¤ à¤¸à¥à¤µà¤¤à¤¨à¥à¤¤à¥à¤°à¤¤à¤¾ à¤à¤° à¤¸à¤®à¤¾à¤¨à¤¤à¤¾ à¤ªà¥à¤°à¤¾à¤ªà¥à¤¤ à¤¹à¥ à¥¤
>à¤à¤¨à¥à¤¹à¥ à¤¬à¥à¤¿à¤¦ à¤à¤° à¤à¤§à¤¨à¥à¤¤à¤°à¤¾à¤¤à¥à¤®à¤¾ à¤à¥ à¤¦à¥à¤¨ à¤ªà¥à¤°à¤¾à¤ªà¥à¤¤ à¤¹à¥ à¤à¤° à¤ªà¤°à¤¸à¥à¤ªà¤° à¤à¤¨à¥à¤¹à¥ à¤à¤¾à¤à¤à¤¾à¤°à¥ à¤à¥ à¤à¤¾à¤µ à¤¸à¥ à¤¬à¤¤à¤¾à¤°à¤µ à¤à¤°à¤¨à¤¾ à¤à¤¾à¤¿à¤¹à¤ à¥¤
>FreeSans
>à¤¸à¤à¥ à¤®à¤¨à¥à¤·à¥à¤¯à¥à¤ à¤à¥ à¤à¥à¤°à¤µ à¤à¤° à¤à¤§à¤¿à¤§à¤¿à¤à¤¾à¤°à¥à¤ à¤à¥ à¤®à¤¾à¤®à¤²à¥ à¤®à¥à¤ à¤à¤¨à¥à¤®à¤à¤¾à¤¤ à¤¸à¥à¤µà¤¤à¤¨à¥à¤¤à¥à¤°à¤¤à¤¾ à¤à¤° à¤¸à¤®à¤¾à¤¨à¤¤à¤¾ à¤ªà¥à¤¾à¤ªà¥à¤¤ à¤¹à¥ à¥¤
>à¤à¤¨à¥à¤¹à¥à¤ à¤¬à¥à¤¿à¤¦à¥à¤§à¤¿ à¤à¤° à¤à¤§à¤¨à¥à¤¤à¤°à¤¾à¤¤à¥à¤®à¤¾ à¤à¥ à¤¦à¥à¤¨ à¤ªà¥à¤¾à¤ªà¥à¤¤ à¤¹à¥ à¤à¤° à¤ªà¤°à¤¸à¥à¤ªà¤° à¤à¤¨à¥à¤¹à¥à¤ à¤à¤¾à¤à¤à¤¾à¤°à¥ à¤à¥ à¤à¤¾à¤µ à¤¸à¥ à¤¬à¤¤à¤¾à¤µ à¤à¤°à¤¨à¤¾ à¤à¤¾à¤¿à¤¹à¤ à¥¤
>Gargi
>à¤¸à¤à¥ à¤®à¤¨à¥à¤·à¥à¤¯à¥ à¤à¥ à¤à¥à¤°à¤µ à¤à¤° à¤à¤§à¤¿à¤§à¤¿à¤à¤¾à¤°à¥ à¤à¥ à¤®à¤¾à¤®à¤²à¥ à¤®à¥ à¤à¤¨à¥à¤®à¤à¤¾à¤¤ à¤¸à¥à¤µà¤¤à¤¨à¥à¤¤à¥à¤°à¤¤à¤¾ à¤à¤° à¤¸à¤®à¤¾à¤¨à¤¤à¤¾ à¤ªà¥à¤°à¤¾à¤ªà¥à¤¤ à¤¹à¥ à¥¤
>à¤à¤¨à¥à¤¹à¥ à¤¬à¥à¤¿à¤¦ à¤à¤° à¤à¤§à¤¨à¥à¤¤à¤°à¤¾à¤¤à¥à¤®à¤¾ à¤à¥ à¤¦à¥à¤¨ à¤ªà¥à¤°à¤¾à¤ªà¥à¤¤ à¤¹à¥ à¤à¤° à¤ªà¤°à¤¸à¥à¤ªà¤° à¤à¤¨à¥à¤¹à¥ à¤à¤¾à¤à¤à¤¾à¤°à¥ à¤à¥ à¤à¤¾à¤µ à¤¸à¥ à¤¬à¤¤à¤¾à¤µ à¤à¤°à¤¨à¤¾ à¤à¤¾à¤¿à¤¹à¤ à¥¤
>
>They're *close*.  I'm very impressed that it re-orders the vowel signs!!!
>Nobody else does that!!!
>
>
>1) All tests show a duplication of letters in the word
>	à¤à¤§à¤¿à¤à¤¾à¤°à¥à¤
>producing
>	à¤à¤§à¤¿à¤§à¤¿à¤à¤¾à¤°à¥à¤
>
>2) The anusvara--the dot on top in à¤®à¥à¤--is lost in most cases.  
>But for this one word, in FreeSans, it isn't lost, and in another, 
>it is lost in FreeSerif and Gargi, but not in Lohit or FreeSans!  
>What's the pattern???
>Gargi has ligature of 094B+0902 it's named uni0972 and not in PUA, which is just a pity.
>FreeSerif also has a ligature dev_o_anusvara.abvs.
>FreeSans does not use this... relies on mark placement.
>Lohit names the same glyph u094B_u0902.abvs.
>I modified the FreeSerif font, placing the anusvara using GPOS positioning.
>Then the anusvara reappeared in the test.
>But something is wrong here.
>	Guess: maybe for these 'abvs' replacements, the AGLFN is being used?
>	Otherwise, for unknown reasons, the anusvara isn't being extracted
>	properly from the ligature glyphs.
>
>3) The word à¤¬à¥à¤¦à¥à¤§à¤¿ is screwed up in every case but in different ways.
>
>	I the last glyph is a ligature, da-dha.  The ligature is decomposed
>	into consonants, but the dha is lost.  Then it gets challenged re-ordering 
>	the vowel sign.
>	(it should be repositioned after the decomposed consonants)
>
>4) Another strange duplication in Lohit only: à¤¬à¤¤à¤¾à¤°à¥à¤¤à¤¾à¤µ
>
>5) FreeSerif, Sans, Gargi: the reph à¤¬à¤°à¥à¤¤à¤¾à¤µ should be transformed back to ra-virama,
>but instead it's lost entirely: à¤¬à¤¤à¤¾à¤µ
>	This information should be gotten from the font's 'rphf' table.
>	All of the fonts have it.  
>	The only difference I see is: Lohit uses an AGLFN name.
>
>6) Weird: à¤à¤¨à¥à¤¤à¤°à¤¾à¤¤à¥à¤®à¤¾ gets a à¤§ (dha) in every case! à¤à¤§à¤¨à¥à¤¤à¤°à¤¾à¤¤à¥à¤®à¤¾
>	Could this be the dha lost in (3)?
> ----------------------------------------------------
>My catch on this:
>
>Clearly you code uses the font's feature tables to construct the PDF file's ToUnicode.
>This is good and right, although hard to do right (and in fact, since the tables
>constitute a many-to-many mapping of glyphs to character strings and ToUnicode is many-to-one, it's impossible to to perfectly).
>
>I suspect you are using the AGLFN.  If that's so, please re-consider.
>In the presence of OpenType tables, glyph names should be ignored.
>The glyph names can at best duplicate what's in the tables. Otherwise
>following the AGLFN *only* causes problems.
>Oh, hell, maybe you could use it to break a tie, when the feature tables
>map the same glyph to two different character strings.
>But please, usually, ignore the AGLFN.  It is not a good thing.
>
>I think this is only a few bugs away from working adequately.
>
>Further things to consider:
>1) the rearrangement of vowels really is necessary.
>2) the OpenType standards for Indic scripts changed in 2005, 
>   making new scripts such as 'dev1' to replace 'deva', 
>   in which several feature tags are changed, notably, 
>   the order of inputs to 'akhn', 'abvf', 'blwf' are altered.

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