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OverviewV-Play 2 Support (Qt 5) › Qt licencing, iOS linking and V-play – current situation

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  • #15101

    Marcin

    Hello,
    Since I am getting closer to do something that I will want to deploy, some iOS problems in QT open source licence appear.
    Have some questions, tried to put only these more v-play related, I hope maybe I will get some answers :)

    From what I have read, forums plus this post https://v-play.net/developers/forums/t/qt-licensing, plus Qt blog, now it is not possible to dynamically link Qt in App Store apps.
    From what I understand, since iOS8 it is possible to use dynamic linking in App store apps.
    The problem is, it not possible yet to use dynamic linking in all Qt modules in open source licenses.
    But is looks like it will be possible soon and it is related to this issue https://codereview.qt-project.org/#/c/123023/
    1.
    So, V-play team, do you think you will start using dynamic linking on iOS devices by default if it is going to be possible(possible I mean with opens source Qt licence)?

    2.
    Currently, if I want to use LGPLv3 I would need to use static linking in App Store for Qt(what V-play does I think) but this requires me to give, on request, source objects of the app.
    What does source objects mean in this context, can I just allow to share binary package of my app compiled with help from extra v-play feature?

    3. It looks like there is a hope to use Qt compiler with opens source license.
    More here: http://blog.qt.io/blog/2016/01/13/new-agreement-with-the-kde-free-qt-foundation/
    Any plans to start using it in v-play by default if this becomes true?
    Or maybe there is no point?
    Or maybe I miss completely the point.

    Thanks,
    Marcin

    #15104

    Alex
    V-Play Team

    Hi Marcin,

    1. Since iOS 8 it is possible to use dynamic linking for app store projects, that’s correct. Qt 5.8 will be the first version that supports building dynamic Qt libraries for iOS. I have however no information if it’s a technical preview or already “stable” enough” as of now. Furthermore I can’t share any plans if and when Qt is planning to switch over to dynamic libraries for their official pre-built packages. As we spend quite a lot of effort to stay compatible with stock Qt installations we stick to the Qt conventions for our default installation, meaning that we will switch over to dynamic libraries as soon as Qt switched over.

    For customers on a paid subscription plan we however do often provide custom built libraries, this will also be the case for dynamic ones with Qt 5.8 I guess.

    2. From a technical viewpoint it is sufficient to provide object files (an intermediate file format which is used by the linker to create the final binary and is not human-readable) from your custom project and the V-Play library itself, which is available as download from our website. In case of a V-Play project this corresponds to two files, an object file from your project’s main.cpp file and an object file containing all your QML files in a binary representation. You can find those two files in the build directory of your project (main.o and qrc_resources.o).

    As always, if you have any concerns using LGPL license, please consult a lawyer for clarification.

    3. Qt Quick Compiler will be available as a project setting, as it is currently within the commercial package. During development it is often easier to disable it, as your app does not instantly crash on a QML error and also build times with quick compiler disabled are a lot faster during development. For a distribution build it adds faster startup times for your app, so this is definitely a feature we are looking forward to see in the open-source variant of Qt.

    Hope this answers your questions!

    Best,

    Alex from V-Play

    #15105

    Marcin

    Hi Alex,
    Very informative, thank you for this.
    Now I understand the whole situation much better.
    As for special builds- if needed will contact you privately.

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