Re: Font Shaping Engine

[विश्वासो वासुकिजः (Vishvas Vasuki)]

+ sanskrit-programmers, shrIramaNa, vinodh, swarup, atul

नमस्ते!

We are looking for collaborators for the below project (it is something we want to accomplish relatively soon) : please let us know if you are can contribute a few hours each week!

​shrI arjuna and his team are behind several projects such as http://advaitasharada.sringeri.net/ and http://sirinudi.org/ , in the course of which they have identified several pressing font problems​ which could easily be solved with the use of web fonts (which is how http://www.mathjax.org/, which renders latex in html pages using javascript, works). As an aside, once this is done, it will be easier to push improvements to 

​

HarfBuzz (which has several lacunae when it comes to Indic fonts).

2015-02-23 4:33 GMT-08:00 Arjun Kashyap <arjun....@srirangadigital.com>:

Here is the statement of work of what we plan to do.

-----------------------------------------------------------------------------------------------------

GOAL: Development of a font shaping engine for Indic Languages 

PROBLEM STATEMENT:

When text is written in Unicode, there 'appears' to be multiple typos when it is viewed in a browser. This problem makes it

very hard for readable documents to be developed and displayed on the internet.  This significant problem has to be solved

​​

before indic languages can be more widely adopted.  The font problem is due to the complex grid based nature of indic scripts.

SOLUTION:

A font shaping engine as a post processor before text is rendered on screen can solve this problem. 

Current font shaping engines available such as

​​

HarfBuzz attempts to solve this. However, these engines are incomplete and do 

not solve the main issues.

 

With an efficient and comprehensive font shaping engine, rendering of Indic scripts can be made uniform across all 

operating systems and browsers. A Javascript library will be developed for font shaping. This library would use HTML5 canvas to display text.

Unicode text is read and text is shaped using the glyphs available in Unicode fonts along with rules written in the library.

ADVANTAGES:

This font shaping engine is critical for significant and faster adoption of indic languages and millions of existing

books in indic languages would be easily accessible and readable. 

ESTIMATED PROJECT ACTIVITIES:

1. Initial research on existing implementation of font shaping engine for Persian and other scripts

2. Development of rules for processing of indic languages - initially for Devanagari and Kannada scripts

3. Implementation of the font shaping engine in Javascript code 

4. Comprehensive testing and release of code

​​

open-source

TIMELINE:

Each of the activities is expected to take about 40 hours for a total of 160 hours. 

-----------------------------------------------------------------------------------------------------

Thanks and Regards

Arjun Kashyap

Managing Director

Sriranga Digital Software Technologies Private Limited

Srirangapatna

+91 94825 84815

--

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Vishvas /विश्वासः

[Anunad Singh]

I am happy to find such a project started. I am keen to contribute but not able to understand what I can/should do.

Elaborating the following points may help-

(1) "When text is written in Unicode, there 'appears' to be multiple typos when it is viewed in a browser."

--> Please elaborate or/and attach a picture .


(2) ADVANTAGES:

" This font shaping engine is critical for significant and faster adoption of indic languages and millions of existing books in indic languages would be easily accessible and readable. "

Does this statement mean that scanned copies of physical books can be made available in text format?

-- Anunad Singh

[विश्वासो वासुकिजः (Vishvas Vasuki)]

(+ mailing list, - individual email ids)

2015-02-24 7:30 GMT-08:00 Arjun Kashyap <arjun....@srirangadigital.com>:

Yes Vishwas, considering portability (JS) and also to iron out various issues (Yes, we can report bugs) we are currently facing we thought about something on the lines of MathJax and KaTeX. I will write to you back with more examples. 

Thanks for your efforts and yes, I will join the mailing list.

Thanks All,

Arjun Kashyap

On Tue, Feb 24, 2015 at 8:51 PM, विश्वासो वासुकिजः (Vishvas Vasuki) <vishvas...@gmail.com> wrote:

Now, very informative messages we got elsewhere (read from top).

---------- Forwarded message ----------
From: Dave Crossland
Date: Mon, Feb 23, 2015 at 11:14 AM
Subject: Re: [Indic] JS font shaping engine for Indic Languages

Hi

https://github.com/prezi/harfbuzz-js might be relevant for your project :)

Cheers,
Dave

​On Mon, Feb 23, 2015 at 11:26 AM, Behdad Esfahbod  wrote:

Not sure what the motivation is, but the time estimates seem off by a factor of more than ten...

Following up with what Dave suggested, see:

  https://prezi.com/zybglpjalpkl/conquering-multi-platform-text-rendering-wwx2013/

  https://mail.google.com/mail/u/0/#inbox/14bb7c3e53c7a74b

Err.  Last link was meant to be this:

  https://www.youtube.com/watch?v=yvQpt6hCzU8

 

behdad

​

[विश्वासो वासुकिजः (Vishvas Vasuki)]

(+ mailing list, - individual email ids)

2015-02-24 7:19 GMT-08:00 विश्वासो वासुकिजः (Vishvas Vasuki) <vishvas...@gmail.com>:

​​

Thank you, all. A major motivation was to have a **javascript** font rendering engine - so that one wouldnt have to worry about what fonts are installed in users' computers, what font renderer they have etc..

In the meantime, we've learned that there exists a HarfBuzz javascript port. (will attach details in next email.) Arjun will consider all this and get back to us.

PS: Arjun - you may want to join this mailing list and elect to get email updates for this thread.

2015-02-24 7:11 GMT-08:00 Shriramana Sharma <sam...@gmail.com>:

On Mon, Feb 23, 2015 at 7:47 PM, विश्वासो वासुकिजः (Vishvas Vasuki)
<vishvas...@gmail.com> wrote:
> + sanskrit-programmers, shrIramaNa, vinodh, swarup, atul
>
> नमस्ते!
>
> We are looking for collaborators for the below project (it is something we
> want to accomplish relatively soon) : please let us know if you are can
> contribute a few hours each week!

I am totally not sure why people are trying to reinvent the wheel.
What is the problem with HarfBuzz? If you find any bugs, please report
them upstream. Behdad is doing a really good job of supporting Indic
scripts. I am not sure what is the level of support for Vedic, but
what would be sensible to do is to actually consolidate all the work
upstream at HarfBuzz. Otherwise, there is meaningless fragmentation
and reduplication of work.

Sorry if I sound harsh, but I seriously do NOT support starting to
write yet another shaping engine for Indic, for the good of all IMHO.

--
Shriramana Sharma ஶ்ரீரமணஶர்மா श्रीरमणशर्मा

--

--
Vishvas /विश्वासः

[Shreevatsa R]

I agree with Behdad and Shriramana Sharma -- these time estimates seem arbitrary and low by *at least* one order of magnitude, and reinventing the wheel (when an excellent and actively maintained open-source one exists) is not the best use of one's time.

It would be better to start by being clear about what exactly the problem is. As Anunad asked, do you have some screenshots of the problems? Simply collecting the existing issues would be a useful first step, before embarking on a mammoth project.

My impression is that today in most cases the issue is with fonts (not with Harfbuzz the font-shaping engine), and simply using decent web fonts (as Mathjax does) with good rules for Indic scripts would solve this issue (on any modern browser), without requiring a font shaping engine to be rewritten from scratch.

At harfbuzz.org there is a link http://goo.gl/FSIQuC to slides from a Nov 2014 talk -- it goes into Indic issues as an example, and should be illustrative of how complex the issue is. IMO it is not something that can be implemented in 40 hours.

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[Shreevatsa R]

[On rereading my previous email, I see that twice (primed by the subject and previous emails) I used the phrase "font shaping engine"; the precise term is "text shaping engine".]

By the way, I am surprised to see Vishvas's statement that "[HarfBuzz] has several lacunae when it comes to Indic fonts", and the one in the quoted email that "Current font shaping engines available such as ​​HarfBuzz [...] are incomplete and do not solve the main issues."

What "main issues" are these? In my experience, I have not encountered a single deficiency in any recent version of HarfBuzz for either Devanagari or Kannada script. Especially over the last couple of years, as more and more projects have moved to HarfBuzz replacing their home-grown buggy or non-existent shaping routines, the overall outcome has been a great boon to Indic scripts.

Even if any issues are found, it would be easier to fix HarfBuzz than to write a replacement from scratch (which is likely to have a similar number of bugs). So why all this wasteful work, when for almost everyone who can benefit from it, the issues (if any!) can be solved with web fonts in a couple of lines of CSS?

If you (the user) don't have good fonts, no shaping engine can help you. If you have good fonts, even the current shaping engines do a fine job.

[That's assuming we're talking about a text shaping engine. I hope the approach doesn't mean painting characters in a HTML5 canvas -- that would be a throwback to putting scanned images on a webpage. :-) The standard approach of having text as text has many benefits -- the text can be selected, copied, searched for, is readable by screen readers and search engines, can be acted-on by extensions, etc.]

[Shreevatsa R]

Here's a concrete example (in Kannada script).

Right now, if I visit http://sirinudi.org/ and view it in Chrome on Mac OS X, I see the following:

Note how both ಶಂಕರಮೂರ್ತಿಯವರು (the fourth word, last in its link) and ಕರ್ನಾಟಕ (penultimate word in top line) are bad. Results on Firefox are even worse:

But WhatFont on Chrome tells me that the font being used for the text is Georgia (not a Kannada font, so some glyph substitution must be happening).

So if I simply open up "Inspect element" and change the CSS to specify font-family as "Kedage" (a Kannada font installed on my system), the displayed text in Chrome (without even reloading the tab) changes:

And similarly in Firefox with Developer->Inspector:

This is with the same text shaping engine as before (which I think is Harfbuzz in both cases).

In this case, if the website had merely specified its set of fonts correctly (or even just language, which is all that kn.wikipedia.org does), everything would have looked fine from the start. If the website additionally wanted to control the font that was used, all it would have to do is specify @font-face in CSS and allow the font to be downloaded as needed (as Mathjax does).

I think any website sophisticated enough to load a custom text shaping engine in its body (assuming one gets written) would also be sophisticated enough to just set fonts correctly. :-) So it's not clear who will be helped by the new shaping engine.

(Also, the issue in my case was a bad font "Kannada MN"; simply disabling all Kannada fonts other than Kedage also fixed things correctly. It may be different on other platforms, but this is just an example that the issue is often not related to the shaping engine; it's more often just a matter of font selection and substitution.)

[विश्वासो वासुकिजः (Vishvas Vasuki)]

​Thanks Shreevatsa - makes sense​. I hope that the "web fonts in a couple of lines of CSS" solution is workable right now - an example would be much appreciated.

2015-02-24 22:18 GMT-08:00 Shreevatsa R <shree...@gmail.com>:

By the way, I am surprised to see Vishvas's statement that "[HarfBuzz] has several lacunae when it comes to Indic fonts",

​I take that back, with apologies - I am so ignorant about the details of how font rendering works that I can't tell what is broken when something fails on Chrome.

 

and the one in the quoted email that "Current font shaping engines available such as ​​HarfBuzz [...] are incomplete and do not solve the main issues."

What "main issues" are these?

​Arjun can address that, once he is done collecting his thoughts.​

[Shreevatsa R]

On Wed, Feb 25, 2015 at 8:03 AM, विश्वासो वासुकिजः (Vishvas Vasuki) <vishvas...@gmail.com> wrote:

​Thanks Shreevatsa - makes sense​. I hope that the "web fonts in a couple of lines of CSS" solution is workable right now - an example would be much appreciated.

See https://developers.google.com/fonts/docs/getting_started for examples. 

Try downloading and opening the attached HTML file (1-devanagari.html) in any modern browser. Even if your computer doesn't have a single Devanagari font installed, it should work.

If you'd like to make your own webpage:

  -- Start at http://www.google.com/fonts 

  -- in the left column under "Script" choose "Devanagari"

  -- pick a font (the top one, Noto Sans, is probably a good choice as it's the default on Android and is being actively worked on) by clicking on the blue "Add To collection". 

  -- In the thing that pops up on the bottom of the screen, click on "Review" (top-right in the bottom pane), then "Use"

  -- follow the instructions on the page.

[Note: right now, Noto Sans Devanagari has a bug: it claims to support Italic even though it doesn't yet; that's just a font bug that will probably get fixed soon, in the meantime just don't style Devanagari text as italic... or pick a different font that you like.]

There are also Kannada fonts at http://www.google.com/fonts/earlyaccess ; download and open the attached 2-kannada.html for example.

You can do crazy things, Dave Crossland has an example at https://gist.github.com/davelab6/11283321 using shading etc.; I've attached that too.

None of these requires the reader to have fonts installed on their system.

I'd be really curious to see what this looks like on different browsers, and whether there are issues in any of them.

[Shreevatsa R]

To reiterate: don't use Gmail's "view attachment" to view those attachments; you need to download the files (e.g. they will be saved with the same names as above, not as "0.html" or anything like that), and then open them in your browser. 

[Shreevatsa R]

BTW, on Linux, HarfBuzz actually provides a great way to see how different fonts do on a given text. Installing it (e.g. with "sudo apt-get install libharfbuzz-bin" on Ubuntu) provides a program called hb-view, which takes a font and text and produces the output in large font size (256 by default). This is the core of what text shaping (the functionality of HarfBuzz) is, so it's instructive.

I just went through the following exercise. (If you're not using Linux / Ubuntu, you can stop reading.)

First remove FreeSans which causes all sorts of trouble for Indic scripts:

sudo apt-get remove fonts-freefont-otf fonts-freefont-ttf otf-freefont ttf-freefont

Next remove all other Devanagari-related fonts (I used apt-cache search devanagari to get this list):

sudo apt-get remove fonts-deva-extra fonts-gargi fonts-lohit-deva fonts-nakula fonts-noto fonts-sahadeva fonts-samyak-deva fonts-sarai ttf-devanagari-fonts ttf-indic-fonts-core

(Most of these will not be installed.)

At this point (after restarting if necessary), any page with Devanagari text should render as just a bunch of boxes.

This is good!

Next, I installed them one by one and ran dpkg -L <package-name> to see what fonts it installs. The list is attached as Ubuntu-Devanagari-fonts-good-and-bad.txt.

Now hb-view can be used to test the fonts:

for f in $(grep .ttf ~/Downloads/devanagari-list.txt); do echo $f; hb-view $f "अत्र"; done

(That's "atra" in Devanagari that I used as test text.)

Trying more and more complex text rules out fonts one by one: Sarai from fonts-sarai (but not the one from ttf-indic-fonts-core!) fails even on अद्य (adya), you can look at कार्त्स्न्यम् (kārtsnyam: most do fine, though some have better ligatures than others), you can similarly try पितॄन् (pitṝn) and कॢप्ति (kḷpti). On this last one, Gargi (only the one from ttf-indic-fonts-core, not the other one) and Samyak Devanagari (from both) screw up badly: basically the way you saw here: https://code.google.com/p/chromium/issues/detail?id=236042

Also, trying अद्ग (adga) showed that Gargi and Lohit-Devanagari don't have the "dga" ligature (puts them side-by-side). So removed them too.

Similarly, trying खड्ग (khaḍga) showed that NotoSans doesn't have the Dga conjunct ligature. (I'm fine with this as the font is otherwise good.)

So my final recommendation, to avoid having *any* bad font on your system, is the following:

sudo apt-get remove fonts-freefont-otf fonts-freefont-ttf otf-freefont ttf-freefont fonts-sarai fonts-samyak-deva ttf-devanagari-fonts ttf-indic-fonts-core fonts-gargi fonts-lohit-deva

And keep only whichever of the following you like (be aware that Sahadeva has "Calcutta"-style vowels, and that NotoSans doesn't have conjuncts for अङ्ग and खड्ग, and Kalimati doesn't do the conjuct श्च... so basically you could probably just keep fonts-nakula and nothing else, but Nakula is also a distinctive and "light" font; your tastes may differ):

fonts-deva-extra

    /usr/share/fonts/truetype/fonts-deva-extra/chandas1-2.ttf

    /usr/share/fonts/truetype/fonts-deva-extra/kalimati.ttf

    /usr/share/fonts/truetype/fonts-deva-extra/samanata.ttf

fonts-nakula

    /usr/share/fonts/truetype/Nakula/nakula.ttf

fonts-noto

    /usr/share/fonts/truetype/noto/NotoSansDevanagariUI-Bold.ttf

    /usr/share/fonts/truetype/noto/NotoSansDevanagari-Regular.ttf

    /usr/share/fonts/truetype/noto/NotoSansDevanagariUI-Regular.ttf

    /usr/share/fonts/truetype/noto/NotoSansDevanagari-Bold.ttf

fonts-sahadeva

    /usr/share/fonts/truetype/Sahadeva/sahadeva.ttf

(Watch out: fonts-deva-extra installs the unwanted fonts-sarai, and then you have to remove fonts-sarai manually.)

You can use https://en.wikibooks.org/wiki/Hindi/Consonant_combinations and http://www.omniglot.com/writing/devanagari_conjuncts.php to test out the ligatures for most of the common conjuncts.

I am pleased to report that after doing this and restarting, I have beautiful and correct Devanagari rendering everywhere.

[विश्वासो वासुकिजः (Vishvas Vasuki)]

Thanks shrIvatsa - This was enormously educational for me. It seems that popular websites such as sanskritdocuments.org are already using this technique  (pic1), but I will keep a link to this trove here. 

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[Shreevatsa R]

Ah wonderful! On that page you have already collected some "text to test", very useful.

So I have to take back my statement of having perfect Devanagari everywhere, as it does not apply to Vedic: Nakula doesn't seem to perfectly handle "Visarga and anusvAra with svara modifiers" (this I can believe may even be a lacuna in HarfBuzz) nor does it have 1CF5  VEDIC SIGN JIHVAMULIYA and 1CF6  VEDIC SIGN UPADHMANIYA.

I am willing to live with that, but let me know if you decide on another font. :-)

I wish the font fallback mechanism in Chrome wasn't so unpredictable that we have to remove fonts just because we are afraid they may get used (there is actually an extension for it but it introduced new issues)... but for now this is ok for me.

And it is nice to see that websites like sanskritdocuments.org are now using web fonts with @font-face.

[The rest of this email is about Kannada fonts on Ubuntu.]

After removing everything:

sudo apt-get remove fonts-freefont-otf fonts-freefont-ttf otf-freefont ttf-freefont

sudo apt-get remove fonts-gubbi fonts-lohit-knda fonts-navilu ttf-indic-fonts-core ttf-kannada-fonts

there are four relevant packages:

fonts-gubbi

    /usr/share/fonts/truetype/Gubbi/Gubbi.ttf

fonts-lohit-knda

    /usr/share/fonts/truetype/lohit-kannada/Lohit-Kannada.ttf

fonts-navilu

    /usr/share/fonts/truetype/Navilu/Navilu.ttf

ttf-kannada-fonts

    /usr/share/fonts/truetype/ttf-kannada-fonts/Kedage-i.ttf

    /usr/share/fonts/truetype/ttf-kannada-fonts/Malige-i.ttf

    /usr/share/fonts/truetype/ttf-kannada-fonts/lohit_kn.ttf

    /usr/share/fonts/truetype/ttf-kannada-fonts/Malige-t.ttf

    /usr/share/fonts/truetype/ttf-kannada-fonts/Kedage-t.ttf

Of these, Navilu is a "handwriting font" that's too whimsical and Malige I didn't like, so I kept just Gubbi and Lohit Kannada:

sudo apt-get install fonts-gubbi fonts-lohit-knda

And now both kn.wikipedia.org and sirinudi.org render fine.

[Mārcis Gasūns]

3-noto-deva-example.html is amazing indeed. I'll test it on my own websites as well, will start with http://samskrtam.ru/

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[Shreevatsa R]

BTW just today I saw http://advaitasharada.sringeri.net/ which is also developed by Sriranga Digital:

Sriranga Digital Software Technologies Private Limited, headed by C S Yogananda (Professor and Head, Dept. of Mathematics, S J College of Engineering, Mysore) and Sri Arjun Kashyap, has been responsible for Technology and Application Infrastructure

and it uses @font-face and looks great.  

So I guess (addressing Sri Arjun Kashyap) that the @font-face method is satisfactory, and the plan to develop another text shaping / rendering engine is dropped as unnecessary? I'd be curious to know if there are still any issues that have been identified.

(http://sirinudi.org/ is still broken, as it does not use @font-face.)

On Wed, Feb 25, 2015 at 11:13 AM, Shreevatsa R <shree...@gmail.com> wrote:

[Mārcis Gasūns]

On Wednesday, 6 May 2015 20:31:13 UTC+3, shreevatsa wrote:

BTW just today I saw http://advaitasharada.sringeri.net/ which is also developed by Sriranga Digital:

Would be great to read an article of how and what they did to get it work in the header. 

[Krishna K]

What is the current status about providing JavaScript based complex-script shaping for various Indic languages?

[विश्वासो वासुकिजः (Vishvas Vasuki)]

2016-05-30 21:08 GMT-07:00 Krishna K <kot...@gmail.com>:

What is the current status about providing JavaScript based complex-script shaping for various Indic languages?

Nothing beyond what was discussed in this thread (ie - every one seems happy with webfonts, and we heard that there is a JS port of harfbuzz, if it should be required).

[Shreevatsa R]

Just curious: Do you have a specific need for doing text layout in Javascript, e.g. a use case where web fonts aren't sufficient?

--

[Krishna K]

I am exploring couple of things: One of them is an Indic script and handwriting tutoring program for children or adults alike. 

I envision the program to show each constituent stroke (or glyph) for Indic words - and how it can (or should) be written by hand. 

It is going to be a browser-based app, so I am looking for a JavaScript based solution that would provide me the glyph substitutions for any given Indic string. I know how to get the individual glyphs (thanks to opentype.js), but I am also looking for glyph substitutions and kerning information. 

I don't want to reinvent the wheel (so to speak). And I know that OpenType fonts has GSUB tables that should provide this information and I am aware HarfBuzz is supposed to give the glyph substitutions, but I have had no luck getting HarfBuzz to run so far. 

-K

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