[Buildroot] [PATCH v8 4/7] package/opencv: add qt5 support

[Samuel Martin]

Thomas,

On Sun, Jul 5, 2015 at 2:57 PM, Thomas Petazzoni
<thomas.petazzoni at free-electrons.com> wrote:
> Dear Samuel Martin,
>
> On Sun,  5 Jul 2015 11:40:26 +0200, Samuel Martin wrote:
>> Starting with the 2.4.6 release, OpenCV supports both Qt4 and Qt5 as GUI
>> toolkit, but only one can be enabled at the same time.
>>
>> Since Buildroot does not support Qt4/Qt5 co-existence, we make the Qt4
>> knob depend on BR2_PACKAGE_QT5.
>>
>> Note that we usually use 'select ...' to express the dependencies
>> between packages, but in this case, we cannot since the Qt4/Qt5
>> co-existence exclusion is not handled by a simple choice, but by some
>> extra dependencies in the choice entries. This makes impossible using
>> 'select ...' for the Qt support knob without triggering a circular
>> dependency at the kconfig level.
>
> Sorry, but parse error here. Since there's a choice between Qt4 and Qt5
> in OpenCV, what is the problem?
>
>> Besides, we already use 'depends on ...' to express the dependencies
>> with some "big" packages (like xorg or libgtk2). qt or qt5* packages
>> are fairly big. So, I don't think it will hurt that much to use a
>> 'depends on ...' statement in this case.
>
> Fair enough with using 'depends on', however if you do it for Qt4 and
> Qt5, please also do it for libgtk2: instead of doing a select
> BR2_PACKAGE_LIBGTK2, do a 'depends on'.
>
>
>> diff --git a/package/opencv/Config.in b/package/opencv/Config.in
>> index d317603..15f68a2 100644
>> --- a/package/opencv/Config.in
>> +++ b/package/opencv/Config.in
>> @@ -60,6 +60,7 @@ choice
>>
>>         The best toolkit to work with OpenCV are, in decreasing order of
>>         preference by the OpenCV build system):
>> +       - Qt5
>>         - Qt4
>>         - gtk2
>>
>> @@ -90,18 +91,36 @@ comment "gtk2 needs X.org and a toolchain w/ wchar, threads, C++"
>>
>>  config BR2_PACKAGE_OPENCV_WITH_QT
>>       bool "qt4"
>> -     depends on BR2_INSTALL_LIBSTDCPP
>> -     depends on BR2_USE_MMU # qt
>> -     select BR2_PACKAGE_QT
>> +     depends on BR2_PACKAGE_QT
>>       select BR2_PACKAGE_QT_STL
>>       select BR2_PACKAGE_QT_GUI_MODULE
>>       select BR2_PACKAGE_QT_TEST
>>       help
>> -       Use Qt with QtTest module and STL support
>> +       Use Qt4 with QtTest and QtGui modules and STL support, as GUI toolkit.
>> +
>> +# no need for a comment about qt availability WRT the toolchain dependencies
>> +# because they are included in the opencv's ones, so already met.
>
> Why do we have this comment here? We have a "depends on" Qt and not a
> "select", so we anyway don't need to replicate the toolchain
> dependencies.
>
>>
>> -comment "qt4 needs a toolchain w/ C++"
>> +comment "qt4 support needs qt"
>>       depends on BR2_USE_MMU # qt
>> -     depends on !BR2_INSTALL_LIBSTDCPP
>> +     depends on !BR2_PACKAGE_QT && !BR2_PACKAGE_QT5
>
> Why !qt && !qt5 ?
>
> Just do depends on !qt. Remember, you are inside a choice, so anyway the
> user can only select *either* qt4 *or* qt5.

Because in BR, we don't support both qt4 and qt5 enabled at the same time.
So if Qt5 is already enabled in the package selection, this comment
should not be visible; hence the !qt5

>
>> +config BR2_PACKAGE_OPENCV_WITH_QT5
>> +     bool "qt5"
>> +     depends on BR2_PACKAGE_QT5
>> +     select BR2_PACKAGE_QT5BASE
>> +     select BR2_PACKAGE_QT5BASE_CONCURRENT
>> +     select BR2_PACKAGE_QT5BASE_GUI
>> +     select BR2_PACKAGE_QT5BASE_WIDGETS
>> +     help
>> +       Use Qt5 with base, concurrent, test, gui and widgets components, as GUI
>> +       toolkit.
>> +
>> +# no need for a comment about qt5 availability WRT the toolchain dependencies
>> +# because they are included in the opencv's ones, so already met.
>> +
>> +comment "qt5 support needs qt5"
>> +     depends on !BR2_PACKAGE_QT && !BR2_PACKAGE_QT5
>
> Same comment as above.

Same reason ;-)

>
> Thanks,
>
> Thomas
> --
> Thomas Petazzoni, CTO, Free Electrons
> Embedded Linux, Kernel and Android engineering
> http://free-electrons.com



-- 
Samuel