CppTools: Do not call GC() more than necessary

Currently GC() is invoked if
   - 5 CppEditors were closed or the last CppEditor was closed
   - a project is about to be removed
   - a session is about to be unloaded

Thus, for the following use cases, too much GC() calls (can) happen:
    - File > Close All
    - Close All Projects and Editors
    - Changing the session

Fixed by introducing a timer.

Change-Id: I9c984d9de735fc8c6ee77a518e9fb5b63dba5881
Reviewed-by: Erik Verbruggen <erik.verbruggen@digia.com>

src/plugins/cpptools/cppmodelmanager.cpp

@@ -233,6 +233,10 @@ CppModelManager::CppModelManager(QObject *parent)
     ProjectExplorer::ProjectExplorerPlugin *pe = ProjectExplorer::ProjectExplorerPlugin::instance();
     QTC_ASSERT(pe, return);
 
+    m_delayedGcTimer = new QTimer(this);
+    m_delayedGcTimer->setSingleShot(true);
+    connect(m_delayedGcTimer, SIGNAL(timeout()), this, SLOT(GC()));
+
     ProjectExplorer::SessionManager *session = pe->session();
     connect(session, SIGNAL(projectAdded(ProjectExplorer::Project*)),
             this, SLOT(onProjectAdded(ProjectExplorer::Project*)));
@@ -240,6 +244,9 @@ CppModelManager::CppModelManager(QObject *parent)
     connect(session, SIGNAL(aboutToRemoveProject(ProjectExplorer::Project*)),
             this, SLOT(onAboutToRemoveProject(ProjectExplorer::Project*)));
 
+    connect(session, SIGNAL(aboutToLoadSession(QString)),
+            this, SLOT(onAboutToLoadSession()));
+
     connect(session, SIGNAL(aboutToUnloadSession(QString)),
             this, SLOT(onAboutToUnloadSession()));
 
@@ -481,7 +488,7 @@ void CppModelManager::deleteCppEditorSupport(TextEditor::BaseTextEditor *textEdi
     ++numberOfClosedEditors;
     if (numberOfOpenEditors == 0 || numberOfClosedEditors == 5) {
         numberOfClosedEditors = 0;
-        GC();
+        delayedGC();
     }
 }
 
@@ -663,6 +670,11 @@ void CppModelManager::onProjectAdded(ProjectExplorer::Project *)
     m_dirty = true;
 }
 
+void CppModelManager::delayedGC()
+{
+    m_delayedGcTimer->start(500);
+}
+
 void CppModelManager::onAboutToRemoveProject(ProjectExplorer::Project *project)
 {
     do {
@@ -671,6 +683,13 @@ void CppModelManager::onAboutToRemoveProject(ProjectExplorer::Project *project)
         m_projectToProjectsInfo.remove(project);
     } while (0);
 
+    delayedGC();
+}
+
+void CppModelManager::onAboutToLoadSession()
+{
+    if (m_delayedGcTimer->isActive())
+        m_delayedGcTimer->stop();
     GC();
 }
 
@@ -683,8 +702,6 @@ void CppModelManager::onAboutToUnloadSession()
         m_projectToProjectsInfo.clear();
         m_dirty = true;
     } while (0);
-
-    GC();
 }
 
 void CppModelManager::onCoreAboutToClose()
@@ -729,6 +746,7 @@ void CppModelManager::GC()
     // Announce removing files and replace the snapshot
     emit aboutToRemoveFiles(notReachableFiles);
     replaceSnapshot(newSnapshot);
+    emit gcFinished();
 }
 
 void CppModelManager::finishedRefreshingSourceFiles(const QStringList &files)

src/plugins/cpptools/cppmodelmanager.h

@@ -39,6 +39,7 @@
 
 #include <QHash>
 #include <QMutex>
+#include <QTimer>
 
 namespace Core { class IEditor; }
 namespace TextEditor { class BaseTextEditorWidget; }
@@ -77,7 +78,6 @@ public:
     virtual CPlusPlus::Snapshot snapshot() const;
     virtual Document::Ptr document(const QString &fileName) const;
     bool replaceDocument(Document::Ptr newDoc);
-    virtual void GC();
 
     void emitDocumentUpdated(CPlusPlus::Document::Ptr doc);
 
@@ -143,18 +143,22 @@ public:
 
 signals:
     void aboutToRemoveFiles(const QStringList &files);
+    void gcFinished(); // Needed for tests.
 
 public slots:
     virtual void updateModifiedSourceFiles();
+    virtual void GC();
 
 private slots:
     // This should be executed in the GUI thread.
     void onAboutToRemoveProject(ProjectExplorer::Project *project);
+    void onAboutToLoadSession();
     void onAboutToUnloadSession();
     void onCoreAboutToClose();
     void onProjectAdded(ProjectExplorer::Project *project);
 
 private:
+    void delayedGC();
     void replaceSnapshot(const CPlusPlus::Snapshot &newSnapshot);
     WorkingCopy buildWorkingCopyList();
 
@@ -207,6 +211,7 @@ private:
     CppFindReferences *m_findReferences;
 
     bool m_enableGC;
+    QTimer *m_delayedGcTimer;
 };
 
 } // namespace Internal

src/plugins/cpptools/cppmodelmanager_test.cpp

@@ -472,6 +472,8 @@ void CppToolsPlugin::test_modelmanager_snapshot_after_two_projects()
 ///            though it might not be actually generated in the build dir.
 void CppToolsPlugin::test_modelmanager_extraeditorsupport_uiFiles()
 {
+    ModelManagerTestHelper helper;
+
     TestDataDirectory testDataDirectory(QLatin1String("testdata_guiproject1"));
     const QString projectFile = testDataDirectory.file(QLatin1String("testdata_guiproject1.pro"));
 
@@ -515,13 +517,15 @@ void CppToolsPlugin::test_modelmanager_extraeditorsupport_uiFiles()
     // Close Project
     ProjectExplorer::SessionManager *sm = pe->session();
     sm->removeProject(project);
-    ModelManagerTestHelper::verifyClean();
+    helper.waitForFinishedGc();
 }
 
 /// QTCREATORBUG-9828: Locator shows symbols of closed files
 /// Check: The garbage collector should be run if the last CppEditor is closed.
 void CppToolsPlugin::test_modelmanager_gc_if_last_cppeditor_closed()
 {
+    ModelManagerTestHelper helper;
+
     TestDataDirectory testDataDirectory(QLatin1String("testdata_guiproject1"));
     const QString file = testDataDirectory.file(QLatin1String("main.cpp"));
 
@@ -541,6 +545,7 @@ void CppToolsPlugin::test_modelmanager_gc_if_last_cppeditor_closed()
 
     // Close file/editor
     em->closeEditor(editor, /*askAboutModifiedEditors=*/ false);
+    helper.waitForFinishedGc();
 
     // Check: File is removed from the snapshpt
     QVERIFY(!mm->workingCopy().contains(file));

src/plugins/cpptools/modelmanagertesthelper.cpp

@@ -55,6 +55,7 @@ ModelManagerTestHelper::ModelManagerTestHelper(QObject *parent) :
     connect(this, SIGNAL(aboutToRemoveProject(ProjectExplorer::Project*)), mm, SLOT(onAboutToRemoveProject(ProjectExplorer::Project*)));
     connect(this, SIGNAL(projectAdded(ProjectExplorer::Project*)), mm, SLOT(onProjectAdded(ProjectExplorer::Project*)));
     connect(mm, SIGNAL(sourceFilesRefreshed(QStringList)), this, SLOT(sourceFilesRefreshed(QStringList)));
+    connect(mm, SIGNAL(gcFinished()), this, SLOT(gcFinished()));
 
     cleanup();
     verifyClean();
@@ -74,6 +75,9 @@ void ModelManagerTestHelper::cleanup()
     QList<ProjectInfo> pies = mm->projectInfos();
     foreach (const ProjectInfo &pie, pies)
         emit aboutToRemoveProject(pie.project().data());
+
+    if (!pies.isEmpty())
+        waitForFinishedGc();
 }
 
 void ModelManagerTestHelper::verifyClean()
@@ -108,9 +112,21 @@ QStringList ModelManagerTestHelper::waitForRefreshedSourceFiles()
     return m_lastRefreshedSourceFiles;
 }
 
+void ModelManagerTestHelper::waitForFinishedGc()
+{
+    m_gcFinished = false;
+
+    while (!m_gcFinished)
+        QCoreApplication::processEvents();
+}
 
 void ModelManagerTestHelper::sourceFilesRefreshed(const QStringList &files)
 {
     m_lastRefreshedSourceFiles = files;
     m_refreshHappened = true;
 }
+
+void ModelManagerTestHelper::gcFinished()
+{
+    m_gcFinished = true;
+}

src/plugins/cpptools/modelmanagertesthelper.h

@@ -84,6 +84,7 @@ public:
     Project *createProject(const QString &name);
 
     QStringList waitForRefreshedSourceFiles();
+    void waitForFinishedGc();
 
 signals:
     void aboutToRemoveProject(ProjectExplorer::Project *project);
@@ -91,8 +92,10 @@ signals:
 
 public slots:
     void sourceFilesRefreshed(const QStringList &files);
+    void gcFinished();
 
 private:
+    bool m_gcFinished;
     bool m_refreshHappened;
     QStringList m_lastRefreshedSourceFiles;
 };