Help with an old regression in text rendering needed

[Milos Sramek]

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 at gmail.com