Qt5 -> KDE5?

Olivier Goffart ogoffart at kde.org
Mon May 9 18:31:18 BST 2011

Le Monday 09 May 2011, Andreas Hartmetz a écrit :
> >  - Do we want to focus on QML, or stay with QWidget?
> I think this one is both obvious and difficult: Everything else being equal
> QML because it is, for all we know now, more "future compatible".
> There are many open questions:

Thanks for the interresting questions.

> - Can we migrate QWidget-based code in some way?


One can imagine some kinf of tool that port the .ui file to qml file, but the 
C++ logic need to be rewriten as well.

> - Which QWidget-based code is considered important? I'm thinking of
>   KXmlGuiWindow and such things here.

I think kdelibs is not the problem here.
But all the existing applications out there, with all their configuration 
Moving to QML is a total rewrite of the UI.  We are lucky if the application 
have a separate UI and Logic, but this is not always the case.

> - Will QML do what we need? Layouts, custom painting and event handling,
> one language for everything (we probably won't get that one).

QML is still very young.  
Nokia focus is obviously embedded, and KDE has slightly different needs 
But that is where KDE come: We need to identify the needs, and push for them 
to be solved, or do it ourself.

> - Can QML work on older hardware? (see Maksim's message)

QML has been designed to work fast with low resources.
Depends how old you want to go.

> - Can QML look and act "native" on the desktop? I don't care if it looks
>   different, but it should be suitable for the given screen dimensions and
>   input devices.


> - Can we realistically pull off a minimal migration in time for the planned
>    release date?

We do not have a planed release date.
KDE 5 do not need to be release the same day of Qt 5

> - What will the users think? -> We should not lose too many user-visible
>   features.

Indeed, there is inside small QWidgets such as QLineEdit, 15 years of 
experience of behaviour. Support for many imput method, accessibility, cross 
platform, languages, ....

QML starts almost from scratch.

> I think it's not looking good for mostly switching to QML and releasing
> KDE5 shortly after Qt5. Even when QML's own issues have been fixed there
> will be a huge amount of work for KDE, part of which can only happen once
> QML is there. Maybe we should simply stay at KDE4/Qt4 for a while and
> release KDE5 for Qt5 when it's done, but no later than in ~2 years if
> possible.
> For developers releasing KDE5 with QT5 and later KDE6 with Qt5 and more QML
> seems tempting, but users won't like it.

We can do KDE5 with Qt5 and QWidget.  QWidget will stay, but only as a second 
class citizen.  And as open gouvernence comes, KDE can be active in 
maintaining QWidgets (But do we have the ressources?)

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