[Development] Backporting QTextLayout Performance Improvements to Qt4

Knoll Lars Lars.Knoll at digia.com
Mon Nov 18 13:29:41 CET 2013

On 18.11.13 11:49, "Milian Wolff" <mail at milianw.de> wrote:

>On Monday 18 November 2013 10:11:40 Knoll Lars wrote:
>> Yes, once the patch is in 5.x and it affects 4.8 as well, it¹s usually
>> to back port.
>I ask b/c back then Eskil wrote:
>> Eskil Abrahamsen Blomfeldt		Sep 5, 2012
>> Patch Set 4: Do not submit
>> I don't think these P3 optimizations should be back-ported to a patch
>> release. Patch releases exist only to increase stability, and that's
>>why we
>> have the commit policy of only allowing critical fixes (regressions,
>> crashes, blatant drawing errors, security). There's already some
>> that an earlier optimization for this same bug has introduced a crash
>> is triggered by Qt Creator (see QTBUG-27140). I'm working to verify it
>> but please be conservative when committing to a patch release branch,
>> that's the only way to avoid destabilization.
>So just to clarify once more, backporting the changes now from Qt5 is OK?
>be OK with only backporting the changes from Qt 5.1 or a similar stable

It’s ok, as long as it fits the policy for patch level releases.

Larger performance issues can fit into that category, but you would need
to find someone to take the time to thoroughly review and test the code on
4.8. Having the code tested and in released version of 5.x helps with
that, but is probably not enough in itself.


>> On 18.11.13 11:06, "Milian Wolff" <mail at milianw.de> wrote:
>> >Hey all,
>> >
>> >I'd like to ask again whether I could backport some performance
>> >improvements
>> >in QTextLayout/QTextEngine from Qt5 to Qt4.
>> >
>> >Most notably there is https://codereview.qt-project.org/#change,34112
>> >which
>> >effects us in Kate/KDE as outlined here:
>> >https://bugs.kde.org/show_bug.cgi?id=225228
>> >
>> >The changeset above was merged in Qt5 and matured there, see
>> >https://codereview.qt-project.org/#change,34118
>> >
>> >What I propose is to sync the current status of QTextLayout/QTextEngine
>> >from
>> >Qt5, put it into a patchset for Qt4 and get it into the next Qt4
>> >
>> >Would this be accepted? Or is there still a policy which forbids
>> >performance
>> >improvements to be merged into Qt4? Considering that the above makes
>> >Kate
>> >editor practically useless for some files (freezes for multiple
>> >I
>> >personally see this as a bug fix anyways...
>> >
>> >Bye
>Milian Wolff
>mail at milianw.de
>Development mailing list
>Development at qt-project.org

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