[Development] Qt 6 co-installability with Qt 5

[Joerg Bornemann]

On 2/16/21 5:36 PM, Thiago Macieira wrote:

> We're simply asking that we make official what is already done everywhere.

Yes, and that's all good, and with 
https://codereview.qt-project.org/c/qt/qtbase/+/334054 we will have an 
offical recommendation.
I will also add a documentation page in the vicinity of 
https://doc.qt.io/qt-6/linux-building.html

The only thing we're still arguing about is how to call the tools in the 
documentation.

To mention that the distro-provided qmake might be called qmake6 can 
(and should) also be done. But to change qmake to qmake6 everywhere in 
the docs is as consistent as not doing anything - as long as we don't 
rename the tools.

Python is brought up a lot as the common example for having multiple 
versions installed (though that will be history soonish as python 2 
support fades out). If I look at its documentation 
https://docs.python.org/3/using/cmdline.html there's *one* mention of 
python3, buried in the description of the -X option. Everything else is 
just python.

> qmake-based applications that support more than one Qt major version are rare.
> Granted, they are more common during the transition period, but since Qt
> Company's decision this time to accelerate transition from 5 to 6, it will be
> less of an impact this time around. Either way, users need to know whether the
> application has been ported to Qt 6 in the first place and the easiest is for
> the authors / maintainers to document that you should use "qmake6 ".

$ cat INSTALL
Prerequisites to build AwesomeApp:
    - Qt x.y.z
    - libotherstuff a.b.c
    - ...

Yes, I see the problem but I still doubt its severity.

Renaming just the three tools you mentioned would be inconsistent.
Renaming all tools is too late.


On 2/17/21 12:47 AM, Lisandro Damián Nicanor Pérez Meyer wrote:

 > Kai: we the maintainers have been asking for the right solution since 
the Qt3 to Qt4 switch.

Obviously not with enough fervor to convince people and in the case of 
Qt6 muuuuch too late in the release process.


BR,

Joerg