QmlProject: Allow opening individual .ui.qml files in "lite" QDS

QDS nowadays provides an option "-qml-lite-designer" that starts it in a
"lite" mode.

When opening QDS from Qt Creator, use the "normal" QDS when a
.qmlproject file is found. Otherwise start it with "-qml-lite-designer".
Switches to Process::startDetached with "-client" and "-qml-lite-
designer" on macOS too, since "open" wouldn't work for instance sharing
depending on the "-qml-lite-designer" option that we can do with the "-
client" option.

Task-number: QTCREATORBUG-31005
Change-Id: Ia9e00e0ed5ecad8c3c383ee46a6fd2594ee7b2e7
Reviewed-by: hjk <hjk@qt.io>
Reviewed-by: Thomas Hartmann <thomas.hartmann@qt.io>

src/plugins/qmlprojectmanager/qdslandingpage.cpp

@@ -87,7 +87,7 @@ void QdsLandingPage::openQds(bool rememberSelection)
 
     auto editor = Core::EditorManager::currentEditor();
     if (editor)
-        openInQDSWithProject(editor->document()->filePath());
+        openInQds(editor->document()->filePath());
 }
 
 void QdsLandingPage::installQds()

src/plugins/qmlprojectmanager/qmlprojectplugin.cpp

@@ -101,17 +101,19 @@ static void clearAlwaysOpenWithMode()
     ICore::settings()->remove(QmlProjectManager::Constants::ALWAYS_OPEN_UI_MODE);
 }
 
-void openQDS(const FilePath &fileName)
+namespace {
+enum class QdsMode { Lite, Full };
+}
+
+static void openQds(const FilePath &fileName, QdsMode mode)
 {
     const FilePath qdsPath = qdsInstallationEntry();
     bool qdsStarted = false;
     qputenv(Constants::enviromentLaunchedQDS, "true");
-    //-a and -client arguments help to append project to open design studio application
-    if (HostOsInfo::isMacHost())
-        qdsStarted = Process::startDetached(
-            {"/usr/bin/open", {"-a", qdsPath.path(), fileName.toUrlishString()}});
-    else
-        qdsStarted = Process::startDetached({qdsPath, {"-client", fileName.toUrlishString()}});
+    const QStringList modeArgument = mode == QdsMode::Lite ? QStringList("-qml-lite-designer")
+                                                           : QStringList();
+    qdsStarted = Process::startDetached(
+        {qdsPath, modeArgument + QStringList({"-client", fileName.toUrlishString()})});
 
     if (!qdsStarted) {
         QMessageBox::warning(ICore::dialogParent(),
@@ -174,37 +176,33 @@ static bool findAndOpenProject(const FilePath &filePath)
 {
     if (Project *project = ProjectManager::projectForFile(filePath)) {
         if (project->projectFilePath().suffix() == "qmlproject") {
-            openQDS(project->projectFilePath());
+            openQds(project->projectFilePath(), QdsMode::Full);
             return true;
         }
         FilePath projectFolder = project->rootProjectDirectory();
         FilePath qmlProjectFile = findQmlProject(projectFolder);
         if (qmlProjectFile.exists()) {
-            openQDS(qmlProjectFile);
+            openQds(qmlProjectFile, QdsMode::Full);
             return true;
         }
     }
 
     FilePath qmlProjectFile = findQmlProjectUpwards(filePath);
     if (qmlProjectFile.exists()) {
-        openQDS(qmlProjectFile);
+        openQds(qmlProjectFile, QdsMode::Full);
         return true;
     }
     return false;
 }
 
-void openInQDSWithProject(const FilePath &filePath)
+void openInQds(const FilePath &filePath)
 {
     if (findAndOpenProject(filePath)) {
-        openQDS(filePath);
+        openQds(filePath, QdsMode::Full);
         //The first one might be ignored when QDS is starting up
-        QTimer::singleShot(4000, [filePath] { openQDS(filePath); });
+        QTimer::singleShot(4000, [filePath] { openQds(filePath, QdsMode::Full); });
     } else {
-        AsynchronousMessageBox::warning(
-            Tr::tr("Qt Design Studio"),
-            Tr::tr("No project file (*.qmlproject) found for Qt Design "
-               "Studio.\nQt Design Studio requires a .qmlproject "
-               "based project to open the .ui.qml file."));
+        openQds(filePath, QdsMode::Lite);
     }
 }
 
@@ -228,7 +226,7 @@ public:
         setDisplayName(Tr::tr("Qt Design Studio"));
         setMimeTypes({Utils::Constants::QMLUI_MIMETYPE});
         setEditorStarter([](const FilePath &filePath, [[maybe_unused]] QString *errorMessage) {
-            openInQDSWithProject(filePath);
+            openInQds(filePath);
             return true;
         });
     }
@@ -480,7 +478,7 @@ void QmlProjectPlugin::openQds(bool permanent)
         hideQmlLandingPage();
 
     if (IEditor *editor = EditorManager::currentEditor())
-        openInQDSWithProject(editor->document()->filePath());
+        openInQds(editor->document()->filePath());
 }
 
 void QmlProjectPlugin::updateQmlLandingPageProjectInfo(const FilePath &projectFile)

src/plugins/qmlprojectmanager/qmlprojectplugin.h

@@ -9,7 +9,6 @@ namespace Core { class IEditor; }
 
 namespace QmlProjectManager::Internal {
 
-void openQDS(const Utils::FilePath &fileName);
 Utils::FilePath qdsInstallationEntry();
 bool qdsInstallationExists();
 bool checkIfEditorIsuiQml(Core::IEditor *editor);
@@ -17,7 +16,7 @@ Utils::FilePath projectFilePath();
 Utils::FilePaths rootCmakeFiles();
 QString qtVersion(const Utils::FilePath &projectFilePath);
 QString qdsVersion(const Utils::FilePath &projectFilePath);
-void openInQDSWithProject(const Utils::FilePath &filePath);
+void openInQds(const Utils::FilePath &filePath);
 const QString readFileContents(const Utils::FilePath &filePath);
 
 } // QmlProject::Internal