Hello,

After checking the problem with Guille, we have the hypothesis of the
source of the problem.
We have seen that accessing Free Type is not thread-safe.
Basically, the FTFace holds a structure that is filled up with the
glyph and its information. As this structure is part of the Font Face
(a font face is a font plus size and attributes), only one request to
a glyph can be executed at the time. As we are sharing the same font
in many places, you will be starting to see the problem.

Also, we have seen that there many accesses to the glyphs outside the
UI process.
This problem started to appear as we starting to use Calypso (but it
is not limited to it), as Calypso uses lazy tabs. The creation of
these tabs is done outside the UI process.

This is only a hack to test our hypothesis.
To fix it correctly we will have to rewrite the drawing of the glyphs
and synchronize the access to the glyph data information. Also, we
want to do it in a way that does not penalize the processing in the UI
process.

I have only patched the code that is used by the rendering of morphic,
other renderings like Athens or any other user using FT should be
correctly rewritten.

Once we are sure that synchronizing the access to FT fixes the
problem, we will do a real fix not a dirty hack like this.

I will be testing this new Image to see if there is an improvement.

I will really love you try to use this image and tell me if you still
find the problem.

There is a PR generating a Pharo8 image (it is called wrong, but... it
is a Pharo8)

32 bits
=====

https://ci.inria.fr/pharo-ci-jenkins2/job/Test%20pending%20pull%20request%20and%20branch%20Pipeline/job/PR-3157/2/artifact/bootstrap-cache/Pharo7.0-PR-32bit-f8c6957.zip

64 bits
=====

https://ci.inria.fr/pharo-ci-jenkins2/job/Test%20pending%20pull%20request%20and%20branch%20Pipeline/job/PR-3157/2/artifact/bootstrap-cache/Pharo7.0-PR-64bit-f8c6957.zip

If somebody is willing to use it in Pharo 7, I can create a PR against
Pharo7 to generate patched P7 images.

Thanks!

-- 
Pablo Tesone.
teso...@gmail.com

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