Designer: Add command line arguments for plugin paths

Add a command line argument for overriding the default plugin path
(useful if you have installed custom designer plugins in a different,
compatible Qt version), and one for adding plugin paths (for example to
separate builds of custom designer plugins that haven't been installed
anywhere).

This feature is only enabled when building with Qt >= 6.7, which added
the option to change the plugin paths for designer.

Change-Id: I990b26056477e3e41c6afe82479383d8bc7c45d0
Reviewed-by: Jarek Kobus <jaroslaw.kobus@qt.io>
Reviewed-by: hjk <hjk@qt.io>
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>

src/plugins/designer/CMakeLists.txt

@@ -1,3 +1,22 @@
+# used in the .json.in
+if(Qt6_VERSION VERSION_GREATER_EQUAL 6.7.0)
+  set(DESIGNER_PLUGIN_ARGUMENTS
+  "\"Arguments\" : [
+    {
+        \"Name\" : \"-designer-qt-pluginpath\",
+        \"Parameter\" : \"path\",
+        \"Description\" : \"Override the default search path for Qt Designer plugins\"
+    },
+    {
+        \"Name\" : \"-designer-pluginpath\",
+        \"Parameter\" : \"path\",
+        \"Description\" : \"Add a custom search path for Qt Designer plugins\"
+    }
+    ],")
+else()
+  set(DESIGNER_PLUGIN_ARGUMENTS)
+endif()
+
 add_qtc_plugin(Designer
   PLUGIN_CLASS FormEditorPlugin
   CONDITION TARGET Qt::DesignerComponentsPrivate AND TARGET Qt::Designer

src/plugins/designer/Designer.json.in

@@ -15,5 +15,6 @@
     "Category" : "Qt Creator",
     "Description" : "Qt Designer integration.",
     "Url" : "http://www.qt.io",
+    ${DESIGNER_PLUGIN_ARGUMENTS}
     ${IDE_PLUGIN_DEPENDENCIES}
 }

src/plugins/designer/formeditor.cpp

@@ -78,6 +78,9 @@ static inline QIcon designerIcon(const QString &iconName)
     return icon;
 }
 
+Q_GLOBAL_STATIC(QString, sQtPluginPath);
+Q_GLOBAL_STATIC(QStringList, sAdditionalPluginPaths);
+
 using namespace Core;
 using namespace Designer::Constants;
 using namespace Utils;
@@ -203,9 +206,24 @@ public:
 
 static FormEditorData *d = nullptr;
 
-FormEditorData::FormEditorData() :
+#if QT_VERSION >= QT_VERSION_CHECK(6, 7, 0)
-    m_formeditor(QDesignerComponents::createFormEditor(nullptr))
+static QStringList designerPluginPaths()
 {
+    const QStringList qtPluginPath = sQtPluginPath->isEmpty()
+                                         ? QDesignerComponents::defaultPluginPaths()
+                                         : QStringList(*sQtPluginPath);
+    return qtPluginPath + *sAdditionalPluginPaths;
+}
+#endif
+
+FormEditorData::FormEditorData()
+{
+#if QT_VERSION >= QT_VERSION_CHECK(6, 7, 0)
+    m_formeditor = QDesignerComponents::createFormEditorWithPluginPaths(designerPluginPaths(),
+                                                                        nullptr);
+#else
+    m_formeditor = QDesignerComponents::createFormEditor(nullptr);
+#endif
     if (Designer::Constants::Internal::debug)
         qDebug() << Q_FUNC_INFO;
     QTC_ASSERT(!d, return);
@@ -871,5 +889,17 @@ void FormEditorData::print()
     printer->setPageOrientation(oldOrientation);
 }
 
+void setQtPluginPath(const QString &qtPluginPath)
+{
+    QTC_CHECK(!d);
+    *sQtPluginPath = qtPluginPath;
+}
+
+void addPluginPath(const QString &pluginPath)
+{
+    QTC_CHECK(!d);
+    sAdditionalPluginPaths->append(pluginPath);
+}
+
 } // namespace Internal
 } // namespace Designer

src/plugins/designer/formeditor.h

@@ -60,5 +60,8 @@ SharedTools::WidgetHost *activeWidgetHost();
 FormWindowEditor *activeEditor();
 QList<Core::IOptionsPage *> optionsPages();
 
+void setQtPluginPath(const QString &qtPluginPath);
+void addPluginPath(const QString &pluginPath);
+
 } // namespace Internal
 } // namespace Designer

src/plugins/designer/formeditorplugin.cpp

@@ -60,7 +60,25 @@ FormEditorPlugin::~FormEditorPlugin()
     delete d;
 }
 
-void FormEditorPlugin::initialize()
+#if QT_VERSION >= QT_VERSION_CHECK(6, 7, 0)
+static void parseArguments(const QStringList &arguments)
+{
+    const auto doWithNext = [arguments](auto it, const std::function<void(QString)> &fun) {
+        ++it;
+        if (it != arguments.cend())
+            fun(*it);
+    };
+    for (auto it = arguments.cbegin(); it != arguments.cend(); ++it) {
+        if (*it == "-designer-qt-pluginpath")
+            doWithNext(it, [](const QString &path) { setQtPluginPath(path); });
+        else if (*it == "-designer-pluginpath")
+            doWithNext(it, [](const QString &path) { addPluginPath(path); });
+    }
+}
+#endif
+
+bool FormEditorPlugin::initialize([[maybe_unused]] const QStringList &arguments,
+                                  [[maybe_unused]] QString *errorString)
 {
     d = new FormEditorPluginPrivate;
 
@@ -91,6 +109,11 @@ void FormEditorPlugin::initialize()
         if (qtr->load(trFile, qtTrPath) || qtr->load(trFile, creatorTrPath))
             QCoreApplication::installTranslator(qtr);
     }
+
+#if QT_VERSION >= QT_VERSION_CHECK(6, 7, 0)
+    parseArguments(arguments);
+#endif
+    return true;
 }
 
 void FormEditorPlugin::extensionsInitialized()

src/plugins/designer/formeditorplugin.h

@@ -24,7 +24,7 @@ private slots:
 #endif
 
 private:
-    void initialize() override;
+    bool initialize(const QStringList &arguments, QString *errorString) override;
     void extensionsInitialized() override;
 
     void switchSourceForm();