Re: Help with an old regression in text rendering needed

Thank you, Caolán, for your suggestions.


The first thing I've tried was to compile the current version with and
without harfbuzz using
./autogen.sh --with-harfbuzz=no
The result was the same (bad).

I am, however, not sure if harfbuzz was really switched off, since in
config.log I can see

$ ./configure --with-harfbuzz=no
--srcdir=/mnt/data/milos/sbox/libreoffice.git --enable-option-checking=fatal
but later
configure:30367: checking which harfbuzz to use
configure:30468: result: internal

and later also
-I/usr/include/harfbuzz
-lharfbuzz -lharfbuzz-icu

I've tried to investigate it bit deeper:

revision mentioned:
bff8fa9 - (2013-05-06 11:08:29 +0200) Enable HarfBuzz by default -
Khaled Hosny

The last good revision according to my bibisection
f0393d7 - (2013-05-06 16:54:53 +0200) [harfbuzz] Fix text width
calculation, 3rd try - Khaled Hosny

The first bad revision according to my bibisection
48ad2f6 - (2013-05-06 12:48:23 +0200) fdo#46808, Convert some code to
getProcessComponentContext

So, they really are from the same day.

I unfortunately cannot compile these revisions, maybe because my
compiter is too new (gcc version 5.4.0 20160609 (Ubuntu
5.4.0-6ubuntu1~16.04.1)). I happens because of std::auto_ptr:
/workdir/unxlngx6.pro/UnpackedTarball/boost/boost/smart_ptr/scoped_ptr.hpp:66:31:
warning: ‘template<class> class std::auto_ptr’ is deprecated
[-Wdeprecated-declarations]
 
How should I use the -Wdeprecated-declarations switch?

thanks
Milos



On 2016-07-20 18:27, Caolán McNamara wrote:
> On Wed, 2016-07-20 at 08:55 +0200, Milos Sramek wrote:
> > Hi,
> >
> > In Brno I would like to present my tools for automated detection and
> > bibisection of interoperability problems between LO an MS Office. My
> > method is currently of limited utility, because there is a problem
> > with
> > rendering of plain text, which affects most documents and overshadows
> > other bugs.
> >
> > I managed to localized the problem by bibisection. I also wanted to
> > investigate it more deeply, but was unable to compile that version.
> > Thus, I would need help from you :).
> >
> > The problem resides in that the text layout changed (as bibisected
> > using  bibisect-43all):
> You don't state the platform you were working on. Was it Linux, if so
> then probably "bff8fa97e16f0f06fddc5545ea36c8bd2b18a580: Enable
> HarfBuzz by default" is what changed during that period.
>
> With text layout there's the vcl level stuff, which is now backed by
> harfbuzz on Linux, and different things on the other platforms.
> Typically we have had "little" differences between out platforms when
> it comes to text layout already. There's a GSOC underway to experiment
> with using harfbuzz on all platforms. In this stack of code different
> features enabled/disabled in the underlying fontconfig can cause other
> differences too.
>
> I presume you've ensured the same fonts are available to LibreOffice as
> MSOffice otherwise you'd not have gotten this far anyway I guess.
>
> There's also some extra "wiggling" of glyphs that writer does on top of
> all this. I never could quite figure out what writer does there or why
> it does it, but that adds some extra variability to things.
>
> I could never get an exact pixel-to-pixel match in the past (ages ago,
> before the harfbuzz rework) so I guess this was also a "slightly-fuzzy" 
> approach in the close-match case.
>
> Maybe there's some way to try disabling kerning in the harfbuzz layer
> to see if that makes a difference in any way.
>
> C.
>
> as an aside, if I was going down the road again of investigating our
> differences in layout vs msoffice I'd probably try getting harfbuzz up
> and running under windows LibreOffice and then see what the differences
> there were between LibreOffice/MSOffice after throwing out all the
> mysterious writer adjustment code. Possibly creating some ultra-dumb
> font that is plain black blocks or something like that.
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-- 
email & jabber: sramek.milos@gmail.com