StudioWelcome: Open design mode if project is opened again

If an already opened project is opened again we swtich to design
mode instead of edit mode and showing an error message.

(cherry picked from commit 68a6b12b5a)
Task-number: QDS-9183
Change-Id: I291e32a9824103a8f14f4fd618cc9211408ff2da
Reviewed-by: Thomas Hartmann <thomas.hartmann@qt.io>

src/plugins/studiowelcome/studiowelcomeplugin.cpp

@@ -4,6 +4,7 @@
 #include "studiowelcomeplugin.h"
 #include "examplecheckout.h"
 
+#include "projectexplorer/target.h"
 #include "qdsnewdialog.h"
 
 #include <app/app_version.h>
@@ -97,6 +98,20 @@ QPointer<QQuickView> s_viewWindow = nullptr;
 QPointer<QQuickWidget> s_viewWidget = nullptr;
 static StudioWelcomePlugin *s_pluginInstance = nullptr;
 
+static Utils::FilePath getMainUiFile()
+{
+    auto project = ProjectExplorer::SessionManager::startupProject();
+    if (!project)
+        return {};
+
+    if (!project->activeTarget())
+        return {};
+
+    auto qmlBuildSystem = qobject_cast<QmlProjectManager::QmlBuildSystem *>(
+        project->activeTarget()->buildSystem());
+    return qmlBuildSystem->mainUiFilePath();
+}
+
 std::unique_ptr<QSettings> makeUserFeedbackSettings()
 {
     QStringList domain = QCoreApplication::organizationDomain().split(QLatin1Char('.'));
@@ -224,8 +239,15 @@ public:
 
         m_blockOpenRecent = true;
         const FilePath projectFile = FilePath::fromVariant(data(index(row, 0), ProjectModel::FilePathRole));
-        if (projectFile.exists())
+        if (projectFile.exists()) {
-            ProjectExplorer::ProjectExplorerPlugin::openProjectWelcomePage(projectFile);
+            const ProjectExplorerPlugin::OpenProjectResult result
+                = ProjectExplorer::ProjectExplorerPlugin::openProject(projectFile);
+            if (!result && !result.alreadyOpen().isEmpty()) {
+                const auto mainUiFile = getMainUiFile();
+                if (mainUiFile.exists())
+                    Core::EditorManager::openEditor(mainUiFile, Utils::Id());
+            };
+        }
 
         resetProjects();
     }