Qt5 port group

[Craig Treleaven]

> On May 9, 2018, at 2:07 PM, Ryan Schmidt <ryandesign at macports.org> wrote:
> 
> 
> On May 9, 2018, at 07:18, Craig Treleaven wrote:
> 
>> On May 8, 2018, at 5:06 AM, Vincent Habchi wrote:
>> 
>>> I was in the process of modifying the Qt5 Port group to allow for choosing the Qt version one wants to link an application against using variants. However, before I go further, I’d like to know if concurrent installations of different Qt5 versions are supported in MacPorts. If not, what I do is just futile.
>> 
>> Um, there are subports for each Qt5 version.  Picking one at random:
>> 
>> $ port info qt57-qtwebkit
>> qt57-qtwebkit @5.7.1_1 (aqua)
>> Variants:             debug, examples, tests, universal
>> 
>> Description:          Tools and Module(s) for Qt Tool Kit 5: Qt WebKit and Qt WebKit Widgets
>> Homepage:             http://qt.io
>> 
>> Extract Dependencies: xz
>> Build Dependencies:   python27, pkgconfig
>> Library Dependencies: fontconfig, icu, leveldb, webp, libxml2, libxslt, zlib, sqlite3, qt57-qtdeclarative, qt57-qtlocation, qt57-qtmultimedia, qt57-qtsensors, qt57-qtwebchannel, qt57-qtxmlpatterns, qt57-qtbase
>> Conflicts with:       qt3, qt3-mac, qt56-qtbase, qt58-qtbase, qt5-qtbase, qt55-qtbase, qt59-qtbase
>> Platforms:            macosx
>> License:              {LGPL-3 GPL-3 OpenSSLException}
>> Maintainers:          Email: mcalhoun at macports.org, GitHub: MarcusCalhoun-Lopez
>>                     Policy: openmaintainer
>> 
>> Notice that the port depends on several Qt5 ports which are all specified at the same level (“57”).  It conflicts with other versions of Qt.
>> 
>> Is that not sufficient?
> 
> My understanding of the fact that they conflict is that there is some latest version of Qt that is compatible with each version of macOS, and that by using the qt5 portgroup, one automatically receives that version. However, in practice, that does not appear to be the case. I see build failures of my Qt-using ports on some macOS versions because the chosen version of Qt is not compatible with that version of macOS.

The automatic upgrading that the portgroup does is a bit scary.  It seemed like it was no time at all that we went from 5.7.1 to 5.10.  (Even though Qt, at the time, said that they didn’t support the latest MacOS version.)  MythTV needed some fixes for Qt 5.10 for some months after MacPorts moved forward.  I still need to do some testing to see if some interface glitches are present with both 5.10 and (say) 5.5.  

I wish the portgroup gave some way to say “I don’t want to be on the bleeding edge but I don’t want to be stuck at Qt 5.x forever, either”.  After all, the vast majority of Linux installs are still running Qt 5.5.  Maybe this is where variants could help.  I don’t have a good solution.

Craig