Add platform plugin arguments to QLibraryInfo/qt.conf.

Make it possible to specify arguments to the platform plugins in a
section of the qt.conf file:

[Platforms]
WindowsArguments=fontengine=freetype

Change-Id: Ia05d0fa004471dcb74c78a88eec3b220ec3c6ad8
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@digia.com>
Reviewed-by: David Faure <david.faure@kdab.com>
Reviewed-by: Paul Olav Tvete <paul.tvete@digia.com>

src/corelib/global/qlibraryinfo.cpp

@@ -40,6 +40,7 @@
 ****************************************************************************/
 
 #include "qdir.h"
+#include "qstringlist.h"
 #include "qfile.h"
 #include "qsettings.h"
 #include "qlibraryinfo.h"
@@ -113,6 +114,8 @@ public:
     }
 };
 
+static const char platformsSection[] = "Platforms";
+
 QLibrarySettings::QLibrarySettings()
     : settings(QLibraryInfoPrivate::findConfiguration())
 {
@@ -132,7 +135,8 @@ QLibrarySettings::QLibrarySettings()
         haveEffectivePaths = children.contains(QLatin1String("EffectivePaths"));
 #endif
         // Backwards compat: an existing but empty file is claimed to contain the Paths section.
-        havePaths = !haveEffectivePaths || children.contains(QLatin1String("Paths"));
+        havePaths = (!haveEffectivePaths && !children.contains(QLatin1String(platformsSection)))
+                    || children.contains(QLatin1String("Paths"));
 #ifndef QT_BOOTSTRAPPED
         if (!havePaths)
             settings.reset(0);
@@ -461,6 +465,33 @@ QLibraryInfo::rawLocation(LibraryLocation loc, PathGroup group)
     return ret;
 }
 
+/*!
+  Returns additional arguments to the platform plugin matching
+  \a platformName which can be specified as a string list using
+  the key \c Arguments in a group called \c Platforms of the
+  \c qt.conf  file.
+
+  sa {Using qt.conf}
+
+  \internal
+
+  \since 5.3
+*/
+
+QStringList QLibraryInfo::platformPluginArguments(const QString &platformName)
+{
+#ifndef QT_BOOTSTRAPPED
+    if (const QSettings *settings = QLibraryInfoPrivate::findConfiguration()) {
+        QString key = QLatin1String(platformsSection);
+        key += QLatin1Char('/');
+        key += platformName;
+        key += QLatin1String("Arguments");
+        return settings->value(key).toStringList();
+    }
+#endif // !QT_BOOTSTRAPPED
+    return QStringList();
+}
+
 /*!
     \enum QLibraryInfo::LibraryLocation
 

src/corelib/global/qlibraryinfo.h

@@ -47,6 +47,8 @@
 
 QT_BEGIN_NAMESPACE
 
+class QStringList;
+
 class Q_CORE_EXPORT QLibraryInfo
 {
 public:
@@ -96,6 +98,8 @@ public:
     static QString rawLocation(LibraryLocation, PathGroup);
 #endif
 
+    static QStringList platformPluginArguments(const QString &platformName);
+
 private:
     QLibraryInfo();
 };

src/gui/kernel/qguiapplication.cpp

@@ -59,6 +59,7 @@
 #include <QtCore/qmutex.h>
 #include <QtCore/private/qthread_p.h>
 #include <QtCore/qdir.h>
+#include <QtCore/qlibraryinfo.h>
 #include <QtDebug>
 #ifndef QT_NO_ACCESSIBILITY
 #include "qaccessible.h"
@@ -892,6 +893,9 @@ static void init_platform(const QString &pluginArgument, const QString &platform
     // Split into platform name and arguments
     QStringList arguments = pluginArgument.split(QLatin1Char(':'));
     const QString name = arguments.takeFirst().toLower();
+    QString argumentsKey = name;
+    argumentsKey[0] = argumentsKey.at(0).toUpper();
+    arguments.append(QLibraryInfo::platformPluginArguments(argumentsKey));
 
    // Create the platform integration.
     QGuiApplicationPrivate::platform_integration = QPlatformIntegrationFactory::create(name, arguments, argc, argv, platformPluginPath);