[vlc-devel] [PATCH] gui: qt: don't condition plugin import based on QT_STATICPLUGIN

[Steve Lhomme]

I've seen the Qt documentation, not that blog post.
The documentation says

"Note: If you are not using qmake to build your plugin you need to make 
sure that the QT_STATICPLUGIN preprocessor macro is defined."

But we are *not* building a plugin. We are using them. And that's 
exactly what's in qplugin.h. QT_STATICPLUGIN has no influence on 
Q_IMPORT_PLUGIN that we use. It has an influence on QT_MOC_EXPORT_PLUGIN 
which is used when *creating* a plugin, as suggested by the documentation.

I can mention that it's a revert of that commit.

On 2021-02-26 15:07, Alexandre Janniaux wrote:
> Hi,
> 
> This is probably about safety when using this [1]:
> 
>> As described in How to Create Qt Plugins, it is possible to switch off
>> the automatic loading of plugins with CONFIG -= import_plugins, but this
>> disables the generation of the weatherinfo_plugin_import.cpp file, and
>> then we would have to do everything manually: add Q_IMPORT_PLUGIN
>> somewhere in our code, define the QT_STATICPLUGIN preprocessor variable
>> and link the plugin (as one has to do without qmake).
> 
> Your commit seems to be a silent revert of
> 
> commit 98ada626762841b5976ca71166fd2b4b970f19ea
> Author: Martell Malone <martellmalone at gmail.com>
> Date:   Tue Nov 25 13:23:38 2014 +0000
> 
>      Qt: add QT_STATICPLUGIN define as per the qt spec
> 
>      The QT spec says we should use QT_STATICPLUGIN defined if building a
>      static plugin.
> 
>      As we are using out own makefile and not a qt .pro project we have to
>      define it ourselves.
> 
>      This is then used to decide if we should import the modules
>      QWindowsIntegrationPlugin and AccessibleFactory as these are not needed
>      on a shared build.
> 
>      Signed-off-by: Jean-Baptiste Kempf <jb at videolan.org>
> 
> What's the rationale behind this change?
> 
> [1]: https://www.qt.io/blog/2014/08/27/qt-weekly-18-static-linking-with-qt
> 
> On Fri, Feb 26, 2021 at 02:17:48PM +0100, Steve Lhomme wrote:
>> QT_STATICPLUGIN is only used to export plugins, it has no impact on importing
>> plugins (see qplugin.h).
>>
>> We even define it on our own when QT_STATIC is set.
>> ---
>>   modules/gui/qt/maininterface/mainui.cpp | 2 +-
>>   modules/gui/qt/qt.cpp                   | 2 --
>>   modules/gui/qt/qt.hpp                   | 4 ----
>>   3 files changed, 1 insertion(+), 7 deletions(-)
>>
>> diff --git a/modules/gui/qt/maininterface/mainui.cpp b/modules/gui/qt/maininterface/mainui.cpp
>> index 61bfc50e2e3..5d1cd1500f5 100644
>> --- a/modules/gui/qt/maininterface/mainui.cpp
>> +++ b/modules/gui/qt/maininterface/mainui.cpp
>> @@ -118,7 +118,7 @@ bool MainUI::setup(QQmlEngine* engine)
>>       {
>>           for(auto& error: m_component->errors())
>>               msg_Err(m_intf, "qml loading %s %s:%u", qtu(error.description()), qtu(error.url().toString()), error.line());
>> -#ifdef QT_STATICPLUGIN
>> +#ifdef QT_STATIC
>>               assert( !"Missing qml modules from qt contribs." );
>>   #else
>>               msg_Err( m_intf, "Install missing modules using your packaging tool" );
>> diff --git a/modules/gui/qt/qt.cpp b/modules/gui/qt/qt.cpp
>> index 6bb0eefdb7a..a2da98b66e8 100644
>> --- a/modules/gui/qt/qt.cpp
>> +++ b/modules/gui/qt/qt.cpp
>> @@ -72,7 +72,6 @@ extern "C" char **environ;
>>    #include <QtPlugin>
>>    #include <QQuickWindow>
>>
>> - #ifdef QT_STATICPLUGIN
>>     Q_IMPORT_PLUGIN(QSvgIconPlugin)
>>     Q_IMPORT_PLUGIN(QSvgPlugin)
>>     Q_IMPORT_PLUGIN(QJpegPlugin)
>> @@ -94,7 +93,6 @@ extern "C" char **environ;
>>      Q_IMPORT_PLUGIN(QWindowsVistaStylePlugin)
>>      Q_IMPORT_PLUGIN(QWindowsIntegrationPlugin)
>>     #endif
>> - #endif
>>   #endif
>>
>>   #ifndef X_DISPLAY_MISSING
>> diff --git a/modules/gui/qt/qt.hpp b/modules/gui/qt/qt.hpp
>> index a283a02e63b..bb3447df546 100644
>> --- a/modules/gui/qt/qt.hpp
>> +++ b/modules/gui/qt/qt.hpp
>> @@ -35,10 +35,6 @@
>>
>>   #include <qconfig.h>
>>
>> -#ifdef QT_STATIC
>> -#define QT_STATICPLUGIN
>> -#endif
>> -
>>   #define QT_NO_CAST_TO_ASCII
>>   #include <QString>
>>   #include <QUrl>
>> --
>> 2.29.2
>>
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