[Interest] Problems with qt_add_qml_module

[Stefan Seefeld]

Hi Nils,

thanks a lot for your elaborate answer. That's very helpful indeed. I still
have a couple of fundamental questions (see my reply to Ulf), but this
gives some good hints.
In fact I think the best way forward might be to set up a little toy
project that has the desired structure, and which lets me explore the
various aspects that are still unclear (e.g. C++ -> QML type name mapping
etc.)

Thanks,


On Tue, Oct 24, 2023 at 11:22 AM Nils Jeisecke <nils.jeisecke at saltation.com>
wrote:

> Hi,
>
> On Tue, Oct 24, 2023 at 4:35 PM Stefan Seefeld <stefan at seefeld.name>
> wrote:
> > So it sounds like I still don't understand what `qt_add_qml_module` is
> doing.
>
> AFAIK it builds a bunch of cmake custom commands that use moc for c++
> and some other tooling for qml files to extract all the type
> information. This then is the basis to the qmlsc, qmltc and plugin
> code generators (qmlRegisterType etc.). All the generated stuff is
> added to the backing target.
>
> I've used these steps to modernize the code base of existing projects:
>
> 1. Port the Qml code to use proper modules. This can be partially
> automated (https://github.com/njeisecke/qml-migration).
>
> 2. Move existing C++ code into proper qml modules, use QML_ELEMENT,
> QML_SINGLETON etc., remove qmlRegisterType and fix the imports in the
> qml files. This means quite some work and usually also comes with some
> restructuring of the code base.
>
> 3. Replace all context properties by QML_SINGLETON classes providing
> all previous context properties as typed class properties.
>
> 4. Fix all qmllint warnings. Your code will work but qmlsc won't
> compile it to C++. There are still lots of places in Qml that make
> typing and type checking hard (e.g. Loader.item can be anything) the
> (undocumented) "as" operator is a great help here. Also inline
> components are somewhat neglected as types by qmllint.
>
> 5. The hardest part: Refactor all Qml code to eliminate all
> "unqualified access". There is a reason why this check is not enabled
> in qmllint by default ;-) The scope lookup rules were a major design
> fault in Qml, leading to uncheckable, uncompilable and hard to
> maintain code.
>
> It's quite an achievement to now have tooling in Qt 6.6 that allows
> this iterative approach to overcome deficiencies inherently built into
> the Qml DNA. Kudos to the Qml team.
>
> You will finally be able to use qmllint for comprehensive type
> checking of the qml/c++ code base which is a huge win for code quality
> and maintenance.
>
> Nils
>


-- 

      ...ich hab' noch einen Koffer in Berlin...
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