Add QQmlEngine::trimComponentCache()

Allow unused data in the engine's component cache to be safely discarded
so that the memory can be freed for other purposes.

Unloading of scripts that are no longer required after trimming unused
components is not yet supported.

Task-number: QTBUG-25653
Change-Id: I37bc9d5592eeb5edceeb34d010a555dcffd11cea
Reviewed-by: Michael Brasser <michael.brasser@nokia.com>

1 files changed, 122 insertions, 2 deletions

diff --git a/tests/auto/qml/qqmlengine/tst_qqmlengine.cpp b/tests/auto/qml/qqmlengine/tst_qqmlengine.cpp
index ab18cdd050..727635ee2c 100644
--- a/tests/auto/qml/qqmlengine/tst_qqmlengine.cpp
+++ b/tests/auto/qml/qqmlengine/tst_qqmlengine.cpp
@@ -39,7 +39,7 @@
 **
 ****************************************************************************/
 
-#include <qtest.h>
+#include "../../shared/util.h"
 #include <QQmlEngine>
 #include <QQmlContext>
 #include <QNetworkAccessManager>
@@ -51,8 +51,10 @@
 #include <QQmlComponent>
 #include <QQmlNetworkAccessManagerFactory>
 #include <QQmlExpression>
+#include <QQmlIncubationController>
+#include <private/qqmlengine_p.h>
 
-class tst_qqmlengine : public QObject
+class tst_qqmlengine : public QQmlDataTest
 {
     Q_OBJECT
 public:
@@ -65,6 +67,8 @@ private slots:
     void contextForObject();
     void offlineStoragePath();
     void clearComponentCache();
+    void trimComponentCache();
+    void trimComponentCache_data();
     void outputWarningsToStandardError();
     void objectOwnership();
     void multipleEngines();
@@ -252,6 +256,122 @@ void tst_qqmlengine::clearComponentCache()
     }
 }
 
+struct ComponentCacheFunctions : public QObject, public QQmlIncubationController
+{
+    Q_OBJECT
+public:
+    QQmlEngine *engine;
+
+    ComponentCacheFunctions(QQmlEngine &e) : engine(&e) {}
+
+    Q_INVOKABLE void trim()
+    {
+        // Wait for any pending deletions to occur
+        QCoreApplication::sendPostedEvents(0, QEvent::DeferredDelete);
+        QCoreApplication::processEvents();
+
+        engine->trimComponentCache();
+    }
+
+    Q_INVOKABLE bool isTypeLoaded(QString file)
+    {
+        return QQmlEnginePrivate::get(engine)->isTypeLoaded(tst_qqmlengine::instance()->testFileUrl(file));
+    }
+
+    Q_INVOKABLE bool isScriptLoaded(QString file)
+    {
+        return QQmlEnginePrivate::get(engine)->isScriptLoaded(tst_qqmlengine::instance()->testFileUrl(file));
+    }
+
+    Q_INVOKABLE void beginIncubation()
+    {
+        startTimer(0);
+    }
+
+    Q_INVOKABLE void waitForIncubation()
+    {
+        while (incubatingObjectCount() > 0) {
+            QCoreApplication::processEvents();
+        }
+    }
+
+private:
+    virtual void timerEvent(QTimerEvent *)
+    {
+        incubateFor(1000);
+    }
+};
+
+void tst_qqmlengine::trimComponentCache()
+{
+    QFETCH(QString, file);
+
+    QQmlEngine engine;
+    ComponentCacheFunctions componentCache(engine);
+    engine.rootContext()->setContextProperty("componentCache", &componentCache);
+    engine.setIncubationController(&componentCache);
+
+    QQmlComponent component(&engine, testFileUrl(file));
+    QVERIFY(component.isReady());
+    QScopedPointer<QObject> object(component.create());
+    QVERIFY(object != 0);
+    QCOMPARE(object->property("success").toBool(), true);
+}
+
+void tst_qqmlengine::trimComponentCache_data()
+{
+    QTest::addColumn<QString>("file");
+
+    // The various tests here are for two types of components: those that are
+    // empty apart from their inherited elements, and those that define new properties.
+    // For each there are five types of composition: extension, aggregation,
+    // aggregation via component, property and object-created-via-transient-component.
+    foreach (const QString &test, (QStringList() << "EmptyComponent"
+                                                 << "VMEComponent"
+                                                 << "EmptyExtendEmptyComponent"
+                                                 << "VMEExtendEmptyComponent"
+                                                 << "EmptyExtendVMEComponent"
+                                                 << "VMEExtendVMEComponent"
+                                                 << "EmptyAggregateEmptyComponent"
+                                                 << "VMEAggregateEmptyComponent"
+                                                 << "EmptyAggregateVMEComponent"
+                                                 << "VMEAggregateVMEComponent"
+                                                 << "EmptyPropertyEmptyComponent"
+                                                 << "VMEPropertyEmptyComponent"
+                                                 << "EmptyPropertyVMEComponent"
+                                                 << "VMEPropertyVMEComponent"
+                                                 << "VMETransientEmptyComponent"
+                                                 << "VMETransientVMEComponent")) {
+        // For these cases, we first test that the component instance keeps the components
+        // referenced, and then that the instantiated object keeps the components referenced
+        for (int i = 1; i <= 2; ++i) {
+            QString name(QString("%1-%2").arg(test).arg(i));
+            QString file(QString("test%1.%2.qml").arg(test).arg(i));
+            QTest::newRow(name.toLatin1().constData()) << file;
+        }
+    }
+
+    // Test that a transient component is correctly referenced
+    QTest::newRow("TransientComponent-1") << "testTransientComponent.1.qml";
+    QTest::newRow("TransientComponent-2") << "testTransientComponent.2.qml";
+
+    // Test that components can be reloaded after unloading
+    QTest::newRow("ReloadComponent") << "testReloadComponent.qml";
+
+    // Test that components are correctly referenced when dynamically loaded
+    QTest::newRow("LoaderComponent") << "testLoaderComponent.qml";
+
+    // Test that components are correctly referenced when incubated
+    QTest::newRow("IncubatedComponent") << "testIncubatedComponent.qml";
+
+    // Test that a top-level omponents is correctly referenced
+    QTest::newRow("TopLevelComponent") << "testTopLevelComponent.qml";
+
+    // TODO:
+    // Test that scripts are unloaded when no longer referenced
+    QTest::newRow("ScriptComponent") << "testScriptComponent.qml";
+}
+
 static QStringList warnings;
 static void msgHandler(QtMsgType, const char *warning)
 {