Lighthouse: Support external plugins.

Add -platformpluginpath command line option that
spesifies an additional directory to scan for 
plugins. Also read QT_QPA_PLATFORM_PLUGIN_PATH.

QlatformIntegrationFacgtory::create() now tries
to load the plugin from the external path first.
Similarly, keys() returns the keys from the
extra path in addition to the "internal" keys

API changes:
QPlatformIntegration::create() and keys() now take
an optional const QString &platformPluginPath.

New file:
externalplugin.pri, contains instructions and a
base setup for building external plugins.

4 files changed, 63 insertions, 9 deletions

diff --git a/src/gui/kernel/qapplication_qpa.cpp b/src/gui/kernel/qapplication_qpa.cpp
index a164c2d..fdbb931 100644
--- a/src/gui/kernel/qapplication_qpa.cpp
+++ b/src/gui/kernel/qapplication_qpa.cpp
@@ -444,11 +444,11 @@ void QApplication::alert(QWidget *, int)
 {
 }
 
-static void init_platform(const QString &name)
+static void init_platform(const QString &name, const QString &platformPluginPath)
 {
-    QApplicationPrivate::platform_integration = QPlatformIntegrationFactory::create(name);
+    QApplicationPrivate::platform_integration = QPlatformIntegrationFactory::create(name, platformPluginPath);
     if (!QApplicationPrivate::platform_integration) {
-        QStringList keys = QPlatformIntegrationFactory::keys();
+        QStringList keys = QPlatformIntegrationFactory::keys(platformPluginPath);
         QString fatalMessage =
             QString::fromLatin1("Failed to load platform plugin \"%1\". Available platforms are: \n").arg(name);
         foreach(QString key, keys) {
@@ -513,6 +513,7 @@ void qt_init(QApplicationPrivate *priv, int type)
     }
 
     QList<QByteArray> pluginList;
+    QString platformPluginPath = QLatin1String(qgetenv("QT_QPA_PLATFORM_PLUGIN_PATH"));
     QString platformName = QLatin1String(qgetenv("QT_QPA_PLATFORM"));
 
     // Get command line params
@@ -527,6 +528,9 @@ void qt_init(QApplicationPrivate *priv, int type)
         if (arg == "-fn" || arg == "-font") {
             if (++i < argc)
                 appFont = QString::fromLocal8Bit(argv[i]);
+        } else if (arg == "-platformpluginpath") {
+            if (++i < argc)
+                platformPluginPath = QLatin1String(argv[i]);
         } else if (arg == "-platform") {
             if (++i < argc)
                 platformName = QLatin1String(argv[i]);
@@ -550,7 +554,7 @@ void qt_init(QApplicationPrivate *priv, int type)
     }
 #endif
 
-    init_platform(platformName);
+    init_platform(platformName, platformPluginPath);
     init_plugins(pluginList);
 
     QColormap::initialize();
diff --git a/src/gui/kernel/qplatformintegrationfactory_qpa.cpp b/src/gui/kernel/qplatformintegrationfactory_qpa.cpp
index 9122e1a..17a130d 100644
--- a/src/gui/kernel/qplatformintegrationfactory_qpa.cpp
+++ b/src/gui/kernel/qplatformintegrationfactory_qpa.cpp
@@ -52,15 +52,27 @@ QT_BEGIN_NAMESPACE
 #if !defined(QT_NO_LIBRARY) && !defined(QT_NO_SETTINGS)
 Q_GLOBAL_STATIC_WITH_ARGS(QFactoryLoader, loader,
     (QPlatformIntegrationFactoryInterface_iid, QLatin1String("/platforms"), Qt::CaseInsensitive))
+Q_GLOBAL_STATIC_WITH_ARGS(QFactoryLoader, directLoader,
+                          (QPlatformIntegrationFactoryInterface_iid, QLatin1String(""), Qt::CaseInsensitive))
 #endif
 
-QPlatformIntegration *QPlatformIntegrationFactory::create(const QString& key)
+QPlatformIntegration *QPlatformIntegrationFactory::create(const QString& key, const QString &platformPluginPath)
 {
     QPlatformIntegration *ret = 0;
     QStringList paramList = key.split(QLatin1Char(':'));
     QString platform = paramList.takeFirst().toLower();
 
 #if !defined(QT_NO_LIBRARY) && !defined(QT_NO_SETTINGS)
+    // Try loading the plugin from platformPluginPath first:
+    if (!platformPluginPath.isEmpty()) {
+        QCoreApplication::addLibraryPath(platformPluginPath);
+        if (QPlatformIntegrationFactoryInterface *factory =
+            qobject_cast<QPlatformIntegrationFactoryInterface*>(directLoader()->instance(platform)))
+            ret = factory->create(key, paramList);
+
+        if (ret)
+            return ret;
+    }
     if (QPlatformIntegrationFactoryInterface *factory = qobject_cast<QPlatformIntegrationFactoryInterface*>(loader()->instance(platform)))
         ret = factory->create(platform, paramList);
 #endif
@@ -74,10 +86,19 @@ QPlatformIntegration *QPlatformIntegrationFactory::create(const QString& key)
 
     \sa create()
 */
-QStringList QPlatformIntegrationFactory::keys()
+QStringList QPlatformIntegrationFactory::keys(const QString &platformPluginPath)
 {
 #if !defined(QT_NO_LIBRARY) && !defined(QT_NO_SETTINGS)
-    QStringList list = loader()->keys();
+    QStringList list;
+
+    if (!platformPluginPath.isEmpty()) {
+        QCoreApplication::addLibraryPath(platformPluginPath);
+        foreach (const QString &key, directLoader()->keys()) {
+            list += key + QString(QLatin1String(" (from %1)")).arg(platformPluginPath);
+        }
+    }
+
+    list += loader()->keys();
 #else
     QStringList list;
 #endif
diff --git a/src/gui/kernel/qplatformintegrationfactory_qpa_p.h b/src/gui/kernel/qplatformintegrationfactory_qpa_p.h
index ba02d2c..77e1da1 100644
--- a/src/gui/kernel/qplatformintegrationfactory_qpa_p.h
+++ b/src/gui/kernel/qplatformintegrationfactory_qpa_p.h
@@ -66,8 +66,8 @@ class QPlatformIntegration;
 class QPlatformIntegrationFactory
 {
 public:
-    static QStringList keys();
-    static QPlatformIntegration *create(const QString&);
+    static QStringList keys(const QString &platformPluginPath = QString());
+    static QPlatformIntegration *create(const QString &key, const QString &platformPluginPath = QString());
 };
 
 QT_END_NAMESPACE
diff --git a/src/plugins/platforms/externalplugin.pri b/src/plugins/platforms/externalplugin.pri
new file mode 100644
index 0000000..54da4d9
--- /dev/null
+++ b/src/plugins/platforms/externalplugin.pri
@@ -0,0 +1,29 @@
+#
+# Lighthouse now has preliminarily support for building and
+# loading platform plugins from outside the Qt source/build
+# tree.
+#
+# 1) Building external plugins:
+#    Set QTDIR to the Qt build directory, copy this file to
+#    the plugin source repository and include it at the top
+#    of the plugin's pro file. Use QT_SOURCE_TREE if you
+#    want to pull in source code from Qt:
+#
+#    include($$QT_SOURCE_TREE/src/plugins/platforms/fontdatabases/genericunix/genericunix.pri)
+#
+# 2) Loading external plugins:
+#    Specify the path to the directory containing the
+#    plugin on the command line, in addition to the
+#    platform name.
+#
+#    ./wiggly -platformPluginPath /path/to/myPlugin -platform gullfaksA
+#
+
+!exists($$(QTDIR)/.qmake.cache) {
+    error("Please set QTDIR to the Qt build directory")
+}
+
+QT_SOURCE_TREE = $$fromfile($$(QTDIR)/.qmake.cache,QT_SOURCE_TREE)
+QT_BUILD_TREE = $$fromfile($$(QTDIR)/.qmake.cache,QT_BUILD_TREE)
+
+include($$QT_SOURCE_TREE/src/plugins/qpluginbase.pri)