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.

1 files changed, 29 insertions, 0 deletions

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)