Occasionally trim the type cache

As loaded components are kept in a cache, they are never removed by the
garbage collector. So, if you periodically create new components, they
leak. This change adds a floating threshold for the number of
components. When that threshold is surpassed trimCache() is called and
unneeded components are removed.

Task-number: QTBUG-42055
Change-Id: I30e3e4ee287f6d34376713668009c67614a50e0c
Reviewed-by: Simon Hausmann <simon.hausmann@theqtcompany.com>

2 files changed, 38 insertions, 0 deletions

diff --git a/tests/auto/qml/qqmltypeloader/data/trim_cache.qml b/tests/auto/qml/qqmltypeloader/data/trim_cache.qml
new file mode 100644
index 0000000000..74303977dd
--- /dev/null
+++ b/tests/auto/qml/qqmltypeloader/data/trim_cache.qml
@@ -0,0 +1,8 @@
+import QtQuick 2.2
+Rectangle
+{
+    objectName: "dings"
+    width: 100
+    height: 100
+    color: "blue"
+}
diff --git a/tests/auto/qml/qqmltypeloader/tst_qqmltypeloader.cpp b/tests/auto/qml/qqmltypeloader/tst_qqmltypeloader.cpp
index 4c5b1f7e63..7045c7cbd4 100644
--- a/tests/auto/qml/qqmltypeloader/tst_qqmltypeloader.cpp
+++ b/tests/auto/qml/qqmltypeloader/tst_qqmltypeloader.cpp
@@ -35,6 +35,9 @@
 #include <QtQml/qqmlengine.h>
 #include <QtQuick/qquickview.h>
 #include <QtQuick/qquickitem.h>
+#include <QtQml/private/qqmlengine_p.h>
+#include <QtQml/private/qqmltypeloader_p.h>
+#include <QtQml/private/qqmlcompiler_p.h>
 #include "../../shared/util.h"
 
 class tst_QQMLTypeLoader : public QQmlDataTest
@@ -44,6 +47,7 @@ class tst_QQMLTypeLoader : public QQmlDataTest
 private slots:
     void testLoadComplete();
     void loadComponentSynchronously();
+    void trimCache();
 };
 
 void tst_QQMLTypeLoader::testLoadComplete()
@@ -73,6 +77,32 @@ void tst_QQMLTypeLoader::loadComponentSynchronously()
     QVERIFY(o);
 }
 
+void tst_QQMLTypeLoader::trimCache()
+{
+    QQmlEngine engine;
+    QQmlTypeLoader &loader = QQmlEnginePrivate::get(&engine)->typeLoader;
+    for (int i = 0; i < 256; ++i) {
+        QUrl url = testFileUrl("trim_cache.qml");
+        url.setQuery(QString::number(i));
+
+        QQmlTypeData *data = loader.getType(url);
+        if (i % 5 == 0) // keep references to some of them so that they aren't trimmed
+            data->compiledData()->addref();
+
+        data->release();
+    }
+
+    for (int i = 0; i < 256; ++i) {
+        QUrl url = testFileUrl("trim_cache.qml");
+        url.setQuery(QString::number(i));
+        if (i % 5 == 0)
+            QVERIFY(loader.isTypeLoaded(url));
+        else if (i < 128)
+            QVERIFY(!loader.isTypeLoaded(url));
+        // The cache is free to keep the others.
+    }
+}
+
 QTEST_MAIN(tst_QQMLTypeLoader)
 
 #include "tst_qqmltypeloader.moc"