Re: dropping QT4 support

[Kai Torben Ohlhus]

On 12/14/19 1:15 PM, John W. Eaton wrote:
> On 11/4/19 10:37 AM, Rik wrote:
>> "John W. Eaton" <address@hidden> wrote:
> 
>>> We discussed dropping support for Qt4 back in March and June of this
>>> year.  I think most of us agreed that it was a good idea but we
>>> haven't followed through.
>>>
>>> If we agree that this is the right move for 6.1, then I'm willing to
>>> do most or all of the work to fix the configure script and start
>>> updating the sources immediately.  If we delay, I think we will have
>>> to wait until after the 6.1 release as this is a fairly big change so
>>> deserves sufficient time for testing.
>>
>> No objection.  The last Qt4 release was December, 2011 or
>> approximately 8 years ago.  Even most long-term release distributions
>> provide only 3 or 5 years support, so the number of users for Octave
>> who require this feature is already very small.
> 
> I thought I would have time to work on this issue by now but all my
> spare moments disappeared.  So for version 6 I think it is best to keep
> support for Qt4 in the sources but consider it unsupported.  Then we can
> move forward with removing support for it early in the version 7
> development cycle.
> 
> jwe
> 
> 

Yes, might be too time consuming removing all Qt4/Qt5 branches for 6.1.
 I can add a note to NEWS similar to 5.1.0 [1]

### Dependencies

- The GUI requires Qt libraries.  The minimum Qt version supported is
  Qt5.X.  Qt4 is no longer supported.

What minor Qt5 revision X in 5.X does Octave support now?  5.9 is a Qt
LTS, supported until middle of 2020 [2].  Compared to some Linux
distributions:

CentOS (7, June 2024 [3])          ==> 5.9.7  [12]
CentOS (8,  May 2029 [3])          ==> 5.11.1 [12]
Debian (Jessie,  June 2020 [7])    ==> 5.3.2  [4]
Debian (Stretch, June 2022 [7])    ==> 5.7.1  [5]
Debian (Buster,       2024 [7])    ==> 5.11.3 [6]
Ubuntu (14.04 LTS, April 2022 [8]) ==> 5.2.1  [9]
Ubuntu (16.04 LTS, April 2024 [8]) ==> 5.5.1  [10]
Ubuntu (18.04 LTS, April 2028 [8]) ==> 5.9.5  [11]

The only blockers here might be Debian Stretch and Ubuntu (16.04).  I
suggest to require 5.9 LTS.  On servers, mostly relying on LTS versions
a lot, there might not be a need for a Qt GUI in customized builds of
newer Octave versions.  Functional octave versions with respective
dependencies are provided by the distributors.

Best,
Kai

[1]:
https://hg.savannah.gnu.org/hgweb/octave/file/f426dd9750a3/etc/NEWS.5#l68
[2]: https://en.wikipedia.org/wiki/Qt_version_history
[3]: https://en.wikipedia.org/wiki/CentOS#End-of-support_schedule
[4]: https://packages.debian.org/jessie/qtbase5-dev
[5]: https://packages.debian.org/stretch/qtbase5-dev
[6]: https://packages.debian.org/buster/qtbase5-dev
[7]: https://en.wikipedia.org/wiki/Debian_version_history#Release_table
[8]: https://en.wikipedia.org/wiki/Ubuntu_version_history#Table_of_versions
[9]: https://packages.ubuntu.com/trusty/allpackages (search "qtbase5-dev")
[10]: https://packages.ubuntu.com/xenial/qtbase5-dev
[11]: https://packages.ubuntu.com/bionic/qtbase5-dev
[12]: yum info qt5-qtbase-devel (on that system)