[konsole] [Bug 401094] Malayalam rendering regression in Konsole 18.08

[Rajeesh K V]

https://bugs.kde.org/show_bug.cgi?id=401094

--- Comment #16 from Rajeesh K V <rajeeshknambiar at gmail.com> ---
Created attachment 124682
  --> https://bugs.kde.org/attachment.cgi?id=124682&action=edit
Konsole 19.12 with Malayalam PoC patch v2

(In reply to Mariusz Glebocki from comment #15)
> Created attachment 124656 [details]
> render preview (2019-12-22)

The rendering on this one is excellent! There is a major catch, though - the
font used is Noto Sans Malayalam which supports only 'reformed' orthography,
meaning many conjuncts are not grouped/present in that font. A font supporting
'traditional' orthography is necessary to see the full spectrum of beauty and
complexity of the script, such as Rachana/Meera which are available in most
distributions. In Fedora 30+, package name is 'smc-{rachana,meera}-fonts'.


> Oops! Right. Working version here:
> https://invent.kde.org/mglebocki/konsole/tree/wip/complex-scripts-support
> There's also a commit which render debug rectangles/tooltips - just
> skip/remove it if you want to build Konsole for regular use.

Applied all 3 top-most patches from that branch on top of 19.12.0 source,
compiled and tested, and the rendering of Malayalam is excellent! 👏

In the attached screenshot, you can see that the bottom portion of a glyph with
 vertical conjunct is cut-off, which is the only minor issue.


> Terminal version of emacs, or the one with its own window? The latter does
> not have terminal limitations.

Emacs, with 'ansi-term' mode (found in one of the mailing list discussions, I
don't use Emacs to independently verify).


> 
> > > * Is there some simplified/alternative way to display the script?
> > 
> > Not sure I understand the question, could you elaborate?
> 
> Kind of like 'ae' can be used instead of 'æ' when there are technical
> limitations.
> I didn't find anything like this for Malayalam, so I guess that's not the
> case here.

Indeed not. Indic languages can form a variety of conjuncts from multiple
characters (up to 4) and those are present in the font as a single glyph
(ligature). Such glyphs do not have a single Unicode code point as they
represent a combination of code points.


> 
> I mean, some console programs which use complex scripts in its interface,
> preferably something more advanced than just printing line of text. They
> would be useful as test cases. So far I'm testing mc with file names written
> in Malayalam.
> 
> https://phabricator.kde.org/F7831279

OK. I'm not aware of a console program using Malayalam in its user interface,
will do a search and report. And the test with 'mc' is certainly a good one. I
can provide test cases for this (the text and corresponding image of expected
rendering). Is there a test case repository where I can contribute these?

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