Create and init QQuickTheme from QtQuickControls2Plugin

Instead of creating and setting the QQuickTheme instance from each
style plugin (e.g. QtQuickControls2MaterialStylePlugin), create the
QQuickTheme instance in QtQuickControls2Plugin when the style is
being resolved, and just pass the instance to be initialized by the
style plugin(s). This avoids the problem that QQuickTheme API was
virtual, and sub-classes created from plugins would have vtables
destroyed before the QQuickTheme was destroyed.

Task-number: QTBUG-67062
Task-number: QTBUG-68087
Change-Id: I19e9ced5296b708c2668c30163389cb3da6be7cf
Reviewed-by: Mitch Curtis <mitch.curtis@qt.io>

23 files changed, 153 insertions, 220 deletions

diff --git a/src/imports/controls/fusion/qquickfusiontheme.cpp b/src/imports/controls/fusion/qquickfusiontheme.cpp
index 78465b6b..ac88563a 100644
--- a/src/imports/controls/fusion/qquickfusiontheme.cpp
+++ b/src/imports/controls/fusion/qquickfusiontheme.cpp
@@ -36,10 +36,13 @@
 
 #include "qquickfusiontheme_p.h"
 
+#include <QtQuickTemplates2/private/qquicktheme_p.h>
+
 QT_BEGIN_NAMESPACE
 
-QQuickFusionTheme::QQuickFusionTheme()
+void QQuickFusionTheme::initialize(QQuickTheme *theme)
 {
+    Q_UNUSED(theme);
 }
 
 QT_END_NAMESPACE
diff --git a/src/imports/controls/fusion/qquickfusiontheme_p.h b/src/imports/controls/fusion/qquickfusiontheme_p.h
index 0cd77f77..814c1919 100644
--- a/src/imports/controls/fusion/qquickfusiontheme_p.h
+++ b/src/imports/controls/fusion/qquickfusiontheme_p.h
@@ -48,16 +48,16 @@
 // We mean it.
 //
 
-#include <QtCore/qvariant.h>
-#include <QtGui/qpalette.h>
-#include <QtQuickTemplates2/private/qquicktheme_p.h>
+#include <QtCore/qglobal.h>
 
 QT_BEGIN_NAMESPACE
 
-class QQuickFusionTheme :  public QQuickTheme
+class QQuickTheme;
+
+class QQuickFusionTheme
 {
 public:
-    explicit QQuickFusionTheme();
+    static void initialize(QQuickTheme *theme);
 };
 
 QT_END_NAMESPACE
diff --git a/src/imports/controls/fusion/qtquickcontrols2fusionstyleplugin.cpp b/src/imports/controls/fusion/qtquickcontrols2fusionstyleplugin.cpp
index 65da8cd7..107b4a2d 100644
--- a/src/imports/controls/fusion/qtquickcontrols2fusionstyleplugin.cpp
+++ b/src/imports/controls/fusion/qtquickcontrols2fusionstyleplugin.cpp
@@ -63,7 +63,7 @@ public:
     void registerTypes(const char *uri) override;
 
     QString name() const override;
-    QQuickTheme *createTheme() const override;
+    void initializeTheme(QQuickTheme *theme) override;
 };
 
 QtQuickControls2FusionStylePlugin::QtQuickControls2FusionStylePlugin(QObject *parent) : QQuickStylePlugin(parent)
@@ -97,9 +97,9 @@ QString QtQuickControls2FusionStylePlugin::name() const
     return QStringLiteral("Fusion");
 }
 
-QQuickTheme *QtQuickControls2FusionStylePlugin::createTheme() const
+void QtQuickControls2FusionStylePlugin::initializeTheme(QQuickTheme *theme)
 {
-    return new QQuickFusionTheme;
+    QQuickFusionTheme::initialize(theme);
 }
 
 QT_END_NAMESPACE
diff --git a/src/imports/controls/imagine/qquickimaginetheme.cpp b/src/imports/controls/imagine/qquickimaginetheme.cpp
index 3499b3cd..a9722fa5 100644
--- a/src/imports/controls/imagine/qquickimaginetheme.cpp
+++ b/src/imports/controls/imagine/qquickimaginetheme.cpp
@@ -36,19 +36,15 @@
 
 #include "qquickimaginetheme_p.h"
 
-#include <QtGui/qfontinfo.h>
+#include <QtQuickTemplates2/private/qquicktheme_p.h>
 
 QT_BEGIN_NAMESPACE
 
-QQuickImagineTheme::QQuickImagineTheme()
-{
-}
-
-void QQuickImagineTheme::resolve()
+void QQuickImagineTheme::initialize(QQuickTheme *theme)
 {
     QFont systemFont;
     systemFont.setFamily(QLatin1String("Open Sans"));
-    setFont(System, systemFont);
+    theme->setFont(QQuickTheme::System, systemFont);
 
     const QColor accentColor = QColor::fromRgb(0x4fc1e9);
     const QColor windowTextColor = QColor::fromRgb(0x434a54);
@@ -64,7 +60,7 @@ void QQuickImagineTheme::resolve()
     systemPalette.setColor(QPalette::WindowText, windowTextColor);
     systemPalette.setColor(QPalette::Disabled, QPalette::Text, disabledWindowTextColor);
     systemPalette.setColor(QPalette::Disabled, QPalette::WindowText, disabledWindowTextColor);
-    setPalette(System, systemPalette);
+    theme->setPalette(QQuickTheme::System, systemPalette);
 }
 
 QT_END_NAMESPACE
diff --git a/src/imports/controls/imagine/qquickimaginetheme_p.h b/src/imports/controls/imagine/qquickimaginetheme_p.h
index 0d569598..d3d43074 100644
--- a/src/imports/controls/imagine/qquickimaginetheme_p.h
+++ b/src/imports/controls/imagine/qquickimaginetheme_p.h
@@ -48,17 +48,16 @@
 // We mean it.
 //
 
-#include <QtQuickTemplates2/private/qquicktheme_p.h>
+#include <QtCore/qglobal.h>
 
 QT_BEGIN_NAMESPACE
 
-class QQuickImagineTheme : public QQuickTheme
+class QQuickTheme;
+
+class QQuickImagineTheme
 {
 public:
-    explicit QQuickImagineTheme();
-
-protected:
-    void resolve() override;
+    static void initialize(QQuickTheme *theme);
 };
 
 QT_END_NAMESPACE
diff --git a/src/imports/controls/imagine/qtquickcontrols2imaginestyleplugin.cpp b/src/imports/controls/imagine/qtquickcontrols2imaginestyleplugin.cpp
index 6dc142c9..490825ff 100644
--- a/src/imports/controls/imagine/qtquickcontrols2imaginestyleplugin.cpp
+++ b/src/imports/controls/imagine/qtquickcontrols2imaginestyleplugin.cpp
@@ -58,7 +58,7 @@ public:
     void registerTypes(const char *uri) override;
 
     QString name() const override;
-    QQuickTheme *createTheme() const override;
+    void initializeTheme(QQuickTheme *theme) override;
 };
 
 QtQuickControls2ImagineStylePlugin::QtQuickControls2ImagineStylePlugin(QObject *parent) : QQuickStylePlugin(parent)
@@ -84,9 +84,9 @@ QString QtQuickControls2ImagineStylePlugin::name() const
     return QStringLiteral("Imagine");
 }
 
-QQuickTheme *QtQuickControls2ImagineStylePlugin::createTheme() const
+void QtQuickControls2ImagineStylePlugin::initializeTheme(QQuickTheme *theme)
 {
-    return new QQuickImagineTheme;
+    QQuickImagineTheme::initialize(theme);
 }
 
 QT_END_NAMESPACE
diff --git a/src/imports/controls/material/qquickmaterialtheme.cpp b/src/imports/controls/material/qquickmaterialtheme.cpp
index 3ab07f6b..f42c0a03 100644
--- a/src/imports/controls/material/qquickmaterialtheme.cpp
+++ b/src/imports/controls/material/qquickmaterialtheme.cpp
@@ -40,14 +40,11 @@
 #include <QtGui/qpa/qplatformdialoghelper.h>
 #include <QtGui/qfont.h>
 #include <QtGui/qfontinfo.h>
+#include <QtQuickTemplates2/private/qquicktheme_p.h>
 
 QT_BEGIN_NAMESPACE
 
-QQuickMaterialTheme::QQuickMaterialTheme()
-{
-}
-
-void QQuickMaterialTheme::resolve()
+void QQuickMaterialTheme::initialize(QQuickTheme *theme)
 {
     QFont systemFont;
     QFont buttonFont;
@@ -78,38 +75,38 @@ void QQuickMaterialTheme::resolve()
 
     const bool dense = QQuickMaterialStyle::variant() == QQuickMaterialStyle::Dense;
     systemFont.setPixelSize(dense ? 13 : 14);
-    setFont(System, systemFont);
+    theme->setFont(QQuickTheme::System, systemFont);
 
     // https://material.io/guidelines/components/buttons.html#buttons-style
     buttonFont.setPixelSize(dense ? 13 : 14);
     buttonFont.setCapitalization(QFont::AllUppercase);
     buttonFont.setWeight(QFont::Medium);
-    setFont(Button, buttonFont);
-    setFont(TabBar, buttonFont);
-    setFont(ToolBar, buttonFont);
+    theme->setFont(QQuickTheme::Button, buttonFont);
+    theme->setFont(QQuickTheme::TabBar, buttonFont);
+    theme->setFont(QQuickTheme::ToolBar, buttonFont);
 
     // https://material.io/guidelines/components/tooltips.html
     toolTipFont.setPixelSize(dense ? 10 : 14);
     toolTipFont.setWeight(QFont::Medium);
-    setFont(ToolTip, toolTipFont);
+    theme->setFont(QQuickTheme::ToolTip, toolTipFont);
 
     itemViewFont.setPixelSize(dense ? 13 : 14);
     itemViewFont.setWeight(QFont::Medium);
-    setFont(ItemView, itemViewFont);
+    theme->setFont(QQuickTheme::ItemView, itemViewFont);
 
     // https://material.io/guidelines/components/lists.html#lists-specs
     listViewFont.setPixelSize(dense ? 13 : 16);
-    setFont(ListView, listViewFont);
+    theme->setFont(QQuickTheme::ListView, listViewFont);
 
     menuItemFont.setPixelSize(dense ? 13 : 16);
-    setFont(Menu, menuItemFont);
-    setFont(MenuBar, menuItemFont);
-    setFont(ComboBox, menuItemFont);
+    theme->setFont(QQuickTheme::Menu, menuItemFont);
+    theme->setFont(QQuickTheme::MenuBar, menuItemFont);
+    theme->setFont(QQuickTheme::ComboBox, menuItemFont);
 
     editorFont.setPixelSize(dense ? 13 : 16);
-    setFont(TextArea, editorFont);
-    setFont(TextField, editorFont);
-    setFont(SpinBox, editorFont);
+    theme->setFont(QQuickTheme::TextArea, editorFont);
+    theme->setFont(QQuickTheme::TextField, editorFont);
+    theme->setFont(QQuickTheme::SpinBox, editorFont);
 }
 
 QT_END_NAMESPACE
diff --git a/src/imports/controls/material/qquickmaterialtheme_p.h b/src/imports/controls/material/qquickmaterialtheme_p.h
index aa50887b..9a1362b8 100644
--- a/src/imports/controls/material/qquickmaterialtheme_p.h
+++ b/src/imports/controls/material/qquickmaterialtheme_p.h
@@ -48,19 +48,16 @@
 // We mean it.
 //
 
-#include <QtCore/qvariant.h>
-#include <QtGui/qfont.h>
-#include <QtQuickTemplates2/private/qquicktheme_p.h>
+#include <QtCore/qglobal.h>
 
 QT_BEGIN_NAMESPACE
 
-class QQuickMaterialTheme : public QQuickTheme
+class QQuickTheme;
+
+class QQuickMaterialTheme
 {
 public:
-    explicit QQuickMaterialTheme();
-
-protected:
-    void resolve() override;
+    static void initialize(QQuickTheme *theme);
 };
 
 QT_END_NAMESPACE
diff --git a/src/imports/controls/material/qtquickcontrols2materialstyleplugin.cpp b/src/imports/controls/material/qtquickcontrols2materialstyleplugin.cpp
index 09dda329..d407af94 100644
--- a/src/imports/controls/material/qtquickcontrols2materialstyleplugin.cpp
+++ b/src/imports/controls/material/qtquickcontrols2materialstyleplugin.cpp
@@ -58,7 +58,7 @@ public:
     void registerTypes(const char *uri) override;
 
     QString name() const override;
-    QQuickTheme *createTheme() const override;
+    void initializeTheme(QQuickTheme *theme) override;
 };
 
 QtQuickControls2MaterialStylePlugin::QtQuickControls2MaterialStylePlugin(QObject *parent) : QQuickStylePlugin(parent)
@@ -92,9 +92,9 @@ QString QtQuickControls2MaterialStylePlugin::name() const
     return QStringLiteral("Material");
 }
 
-QQuickTheme *QtQuickControls2MaterialStylePlugin::createTheme() const
+void QtQuickControls2MaterialStylePlugin::initializeTheme(QQuickTheme *theme)
 {
-    return new QQuickMaterialTheme;
+    QQuickMaterialTheme::initialize(theme);
 }
 
 QT_END_NAMESPACE
diff --git a/src/imports/controls/qquickdefaulttheme.cpp b/src/imports/controls/qquickdefaulttheme.cpp
index a988c10b..bc292c2f 100644
--- a/src/imports/controls/qquickdefaulttheme.cpp
+++ b/src/imports/controls/qquickdefaulttheme.cpp
@@ -36,13 +36,11 @@
 
 #include "qquickdefaulttheme_p.h"
 
-QT_BEGIN_NAMESPACE
+#include <QtQuickTemplates2/private/qquicktheme_p.h>
 
-QQuickDefaultTheme::QQuickDefaultTheme()
-{
-}
+QT_BEGIN_NAMESPACE
 
-void QQuickDefaultTheme::resolve()
+void QQuickDefaultTheme::initialize(QQuickTheme *theme)
 {
     QPalette systemPalette;
 
@@ -85,7 +83,7 @@ void QQuickDefaultTheme::resolve()
     systemPalette.setColor(QPalette::WindowText, QColor::fromRgba(0xFF26282A));
     systemPalette.setColor(QPalette::Disabled, QPalette::WindowText, QColor::fromRgba(0xFFBDBEBF));
 
-    setPalette(System, systemPalette);
+    theme->setPalette(QQuickTheme::System, systemPalette);
 }
 
 QT_END_NAMESPACE
diff --git a/src/imports/controls/qquickdefaulttheme_p.h b/src/imports/controls/qquickdefaulttheme_p.h
index f372b111..3a7311c7 100644
--- a/src/imports/controls/qquickdefaulttheme_p.h
+++ b/src/imports/controls/qquickdefaulttheme_p.h
@@ -48,17 +48,16 @@
 // We mean it.
 //
 
-#include <QtQuickTemplates2/private/qquicktheme_p.h>
+#include <QtCore/qglobal.h>
 
 QT_BEGIN_NAMESPACE
 
-class QQuickDefaultTheme : public QQuickTheme
+class QQuickTheme;
+
+class QQuickDefaultTheme
 {
 public:
-    explicit QQuickDefaultTheme();
-
-protected:
-    void resolve() override;
+    static void initialize(QQuickTheme *theme);
 };
 
 QT_END_NAMESPACE
diff --git a/src/imports/controls/qtquickcontrols2plugin.cpp b/src/imports/controls/qtquickcontrols2plugin.cpp
index e1b683e8..553060a1 100644
--- a/src/imports/controls/qtquickcontrols2plugin.cpp
+++ b/src/imports/controls/qtquickcontrols2plugin.cpp
@@ -37,10 +37,9 @@
 #include <QtCore/qdir.h>
 #include <QtCore/qfile.h>
 #include <QtCore/qfileinfo.h>
-#if !defined(QT_STATIC) && QT_CONFIG(library)
-#include <QtCore/qlibrary.h>
-#endif
+#include <QtCore/qpluginloader.h>
 #include <QtCore/private/qfileselector_p.h>
+#include <QtQml/qqmlfile.h>
 #include <QtQml/private/qqmldirparser_p.h>
 #include <QtQuickControls2/qquickstyle.h>
 #include <QtQuickControls2/private/qquickchecklabel_p.h>
@@ -59,6 +58,7 @@
 #include <QtQuickTemplates2/private/qquickoverlay_p.h>
 #include <QtQuickControls2/private/qquickclippedtext_p.h>
 #include <QtQuickControls2/private/qquickitemgroup_p.h>
+#include <QtQuickTemplates2/private/qquicktheme_p_p.h>
 
 #include "qquickdefaultbusyindicator_p.h"
 #include "qquickdefaultdial_p.h"
@@ -80,12 +80,11 @@ public:
     void registerTypes(const char *uri) override;
 
     QString name() const override;
-    QQuickTheme *createTheme() const override;
+    void initializeTheme(QQuickTheme *theme) override;
 
-#if !defined(QT_STATIC) && QT_CONFIG(library)
 private:
-    void loadStylePlugin();
-#endif
+    QList<QQuickStylePlugin *> loadStylePlugins();
+    QQuickTheme *createTheme(const QString &name);
 };
 
 QtQuickControls2Plugin::QtQuickControls2Plugin(QObject *parent) : QQuickStylePlugin(parent)
@@ -106,6 +105,11 @@ static QUrl fixupBaseUrl(QQmlExtensionPlugin *plugin)
 #endif
 }
 
+static bool isDefaultStyle(const QString &style)
+{
+    return style.isEmpty() || style.compare(QStringLiteral("Default"), Qt::CaseInsensitive) == 0;
+}
+
 void QtQuickControls2Plugin::registerTypes(const char *uri)
 {
     QQuickStylePrivate::init(fixupBaseUrl(this));
@@ -114,10 +118,15 @@ void QtQuickControls2Plugin::registerTypes(const char *uri)
     if (!style.isEmpty())
         QFileSelectorPrivate::addStatics(QStringList() << style.toLower());
 
-#if !defined(QT_STATIC) && QT_CONFIG(library)
-    // load the style's plugin to get access to its resources
-    loadStylePlugin();
-#endif
+    QQuickTheme *theme = createTheme(style.isEmpty() ? name() : style);
+    if (isDefaultStyle(style))
+        initializeTheme(theme);
+
+    // load the style's plugins to get access to its resources and initialize the theme
+    QList<QQuickStylePlugin *> stylePlugins = loadStylePlugins();
+    for (QQuickStylePlugin *stylePlugin : stylePlugins)
+        stylePlugin->initializeTheme(theme);
+    qDeleteAll(stylePlugins);
 
     qmlRegisterModule(uri, 2, QT_VERSION_MINOR - 7); // Qt 5.7->2.0, 5.8->2.1, 5.9->2.2...
 
@@ -229,45 +238,69 @@ QString QtQuickControls2Plugin::name() const
     return QStringLiteral("Default");
 }
 
-QQuickTheme *QtQuickControls2Plugin::createTheme() const
+void QtQuickControls2Plugin::initializeTheme(QQuickTheme *theme)
 {
-    return new QQuickDefaultTheme;
+    QQuickDefaultTheme::initialize(theme);
 }
 
-#if !defined(QT_STATIC) && QT_CONFIG(library)
-void QtQuickControls2Plugin::loadStylePlugin()
+QList<QQuickStylePlugin *> QtQuickControls2Plugin::loadStylePlugins()
 {
-    QFileInfo fileInfo = resolvedUrl(QStringLiteral("qmldir")).toLocalFile();
-    if (!fileInfo.exists() || fileInfo.path() == baseUrl().toLocalFile())
-        return;
-
-    QFile file(fileInfo.filePath());
-    if (!file.open(QIODevice::ReadOnly | QIODevice::Text))
-        return;
-
-    QQmlDirParser parser;
-    parser.parse(QString::fromUtf8(file.readAll()));
-    if (parser.hasError())
-        return;
-
-    QLibrary lib;
-    lib.setLoadHints(QLibrary::PreventUnloadHint);
-    const auto plugins = parser.plugins();
-    for (const QQmlDirParser::Plugin &plugin : plugins) {
-        QDir dir = fileInfo.dir();
-        if (!plugin.path.isEmpty() && !dir.cd(plugin.path))
-            continue;
-        QString filePath = dir.filePath(plugin.name);
+    QList<QQuickStylePlugin *> stylePlugins;
+
+    QFileInfo fileInfo = QQmlFile::urlToLocalFileOrQrc(resolvedUrl(QStringLiteral("qmldir")));
+    if (fileInfo.exists() && fileInfo.path() != QQmlFile::urlToLocalFileOrQrc(baseUrl())) {
+        QFile file(fileInfo.filePath());
+        if (file.open(QIODevice::ReadOnly | QIODevice::Text)) {
+            QQmlDirParser parser;
+            parser.parse(QString::fromUtf8(file.readAll()));
+            if (!parser.hasError()) {
+#ifdef QT_STATIC
+                const auto plugins = QPluginLoader::staticInstances();
+                for (QObject *instance : plugins) {
+                    QQuickStylePlugin *stylePlugin = qobject_cast<QQuickStylePlugin *>(instance);
+                    if (!stylePlugin || parser.className() != QLatin1String(instance->metaObject()->className()))
+                        continue;
+                    stylePlugins += stylePlugin;
+                }
+#elif QT_CONFIG(library)
+                QPluginLoader loader;
+                const auto plugins = parser.plugins();
+                for (const QQmlDirParser::Plugin &plugin : plugins) {
+                    QDir dir = fileInfo.dir();
+                    if (!plugin.path.isEmpty() && !dir.cd(plugin.path))
+                        continue;
+                    QString filePath = dir.filePath(plugin.name);
 #if defined(Q_OS_MACOS) && defined(QT_DEBUG)
-        // Avoid mismatching plugins on macOS so that we don't end up loading both debug and
-        // release versions of the same Qt libraries (due to the plugin's dependencies).
-        filePath += QStringLiteral("_debug");
+                    // Avoid mismatching plugins on macOS so that we don't end up loading both debug and
+                    // release versions of the same Qt libraries (due to the plugin's dependencies).
+                    filePath += QStringLiteral("_debug");
 #endif // Q_OS_MACOS && QT_DEBUG
-        lib.setFileName(filePath);
-        lib.load();
+                    loader.setFileName(filePath);
+                    QQuickStylePlugin *stylePlugin = qobject_cast<QQuickStylePlugin *>(loader.instance());
+                    if (stylePlugin)
+                        stylePlugins += stylePlugin;
+                }
+#endif
+            }
+        }
     }
+    return stylePlugins;
+}
+
+QQuickTheme *QtQuickControls2Plugin::createTheme(const QString &name)
+{
+    QQuickTheme *theme = new QQuickTheme;
+#if QT_CONFIG(settings)
+    QQuickThemePrivate *p = QQuickThemePrivate::get(theme);
+    QSharedPointer<QSettings> settings = QQuickStylePrivate::settings(name);
+    if (settings) {
+        p->defaultFont.reset(QQuickStylePrivate::readFont(settings));
+        p->defaultPalette.reset(QQuickStylePrivate::readPalette(settings));
+    }
+#endif
+    QQuickThemePrivate::instance.reset(theme);
+    return theme;
 }
-#endif // !QT_STATIC && QT_CONFIG(library)
 
 QT_END_NAMESPACE
 
diff --git a/src/imports/controls/universal/qquickuniversaltheme.cpp b/src/imports/controls/universal/qquickuniversaltheme.cpp
index 6485afbc..041dce9e 100644
--- a/src/imports/controls/universal/qquickuniversaltheme.cpp
+++ b/src/imports/controls/universal/qquickuniversaltheme.cpp
@@ -36,16 +36,12 @@
 
 #include "qquickuniversaltheme_p.h"
 
-#include <QtGui/qfont.h>
 #include <QtGui/qfontinfo.h>
+#include <QtQuickTemplates2/private/qquicktheme_p.h>
 
 QT_BEGIN_NAMESPACE
 
-QQuickUniversalTheme::QQuickUniversalTheme()
-{
-}
-
-void QQuickUniversalTheme::resolve()
+void QQuickUniversalTheme::initialize(QQuickTheme *theme)
 {
     QFont systemFont;
     QFont groupBoxTitleFont;
@@ -60,15 +56,15 @@ void QQuickUniversalTheme::resolve()
     }
 
     systemFont.setPixelSize(15);
-    setFont(System, systemFont);
+    theme->setFont(QQuickTheme::System, systemFont);
 
     groupBoxTitleFont.setPixelSize(15);
     groupBoxTitleFont.setWeight(QFont::DemiBold);
-    setFont(GroupBox, groupBoxTitleFont);
+    theme->setFont(QQuickTheme::GroupBox, groupBoxTitleFont);
 
     tabButtonFont.setPixelSize(24);
     tabButtonFont.setWeight(QFont::Light);
-    setFont(TabBar, tabButtonFont);
+    theme->setFont(QQuickTheme::TabBar, tabButtonFont);
 }
 
 QT_END_NAMESPACE
diff --git a/src/imports/controls/universal/qquickuniversaltheme_p.h b/src/imports/controls/universal/qquickuniversaltheme_p.h
index f0f18db5..f762d0e3 100644
--- a/src/imports/controls/universal/qquickuniversaltheme_p.h
+++ b/src/imports/controls/universal/qquickuniversaltheme_p.h
@@ -48,18 +48,16 @@
 // We mean it.
 //
 
-#include <QtGui/qfont.h>
-#include <QtQuickTemplates2/private/qquicktheme_p.h>
+#include <QtCore/qglobal.h>
 
 QT_BEGIN_NAMESPACE
 
-class QQuickUniversalTheme : public QQuickTheme
+class QQuickTheme;
+
+class QQuickUniversalTheme
 {
 public:
-    explicit QQuickUniversalTheme();
-
-protected:
-    void resolve() override;
+    static void initialize(QQuickTheme *theme);
 };
 
 QT_END_NAMESPACE
diff --git a/src/imports/controls/universal/qtquickcontrols2universalstyleplugin.cpp b/src/imports/controls/universal/qtquickcontrols2universalstyleplugin.cpp
index edc14327..1265f636 100644
--- a/src/imports/controls/universal/qtquickcontrols2universalstyleplugin.cpp
+++ b/src/imports/controls/universal/qtquickcontrols2universalstyleplugin.cpp
@@ -55,7 +55,7 @@ public:
     void registerTypes(const char *uri) override;
 
     QString name() const override;
-    QQuickTheme *createTheme() const override;
+    void initializeTheme(QQuickTheme *theme) override;
 };
 
 QtQuickControls2UniversalStylePlugin::QtQuickControls2UniversalStylePlugin(QObject *parent) : QQuickStylePlugin(parent)
@@ -85,9 +85,9 @@ QString QtQuickControls2UniversalStylePlugin::name() const
     return QStringLiteral("Universal");
 }
 
-QQuickTheme *QtQuickControls2UniversalStylePlugin::createTheme() const
+void QtQuickControls2UniversalStylePlugin::initializeTheme(QQuickTheme *theme)
 {
-    return new QQuickUniversalTheme;
+    QQuickUniversalTheme::initialize(theme);
 }
 
 QT_END_NAMESPACE
diff --git a/src/quickcontrols2/qquickstyleplugin.cpp b/src/quickcontrols2/qquickstyleplugin.cpp
index c42ba88d..553a6cad 100644
--- a/src/quickcontrols2/qquickstyleplugin.cpp
+++ b/src/quickcontrols2/qquickstyleplugin.cpp
@@ -39,14 +39,11 @@
 #include "qquickstyle_p.h"
 #include "qquickstyleselector_p.h"
 
-#include <QtQuickTemplates2/private/qquicktheme_p_p.h>
-
 QT_BEGIN_NAMESPACE
 
 class QQuickStylePluginPrivate
 {
 public:
-    QQuickTheme *theme = nullptr;
     mutable QScopedPointer<QQuickStyleSelector> selector;
 };
 
@@ -57,51 +54,6 @@ QQuickStylePlugin::QQuickStylePlugin(QObject *parent)
 
 QQuickStylePlugin::~QQuickStylePlugin()
 {
-    Q_D(QQuickStylePlugin);
-    if (QQuickTheme::instance() == d->theme)
-        QQuickThemePrivate::instance.reset();
-}
-
-void QQuickStylePlugin::registerTypes(const char *uri)
-{
-    Q_UNUSED(uri);
-}
-
-void QQuickStylePlugin::initializeEngine(QQmlEngine *engine, const char *uri)
-{
-    Q_D(QQuickStylePlugin);
-    Q_UNUSED(engine);
-    Q_UNUSED(uri);
-
-    // make sure not to re-create the theme if initializeEngine()
-    // is called multiple times, like in case of qml2puppet (QTBUG-54995)
-    if (d->theme)
-        return;
-
-    if (isCurrent()) {
-        d->theme = createTheme();
-        if (d->theme) {
-#if QT_CONFIG(settings)
-            QQuickThemePrivate *p = QQuickThemePrivate::get(d->theme);
-            QSharedPointer<QSettings> settings = QQuickStylePrivate::settings(name());
-            if (settings) {
-                p->defaultFont.reset(QQuickStylePrivate::readFont(settings));
-                p->defaultPalette.reset(QQuickStylePrivate::readPalette(settings));
-            }
-#endif
-            QQuickThemePrivate::instance.reset(d->theme);
-        }
-    }
-}
-
-bool QQuickStylePlugin::isCurrent() const
-{
-    QString style = QQuickStyle::name();
-    if (style.isEmpty())
-        style = QStringLiteral("Default");
-
-    const QString theme = name();
-    return theme.compare(style, Qt::CaseInsensitive) == 0;
 }
 
 QString QQuickStylePlugin::name() const
@@ -109,9 +61,9 @@ QString QQuickStylePlugin::name() const
     return QString();
 }
 
-QQuickTheme *QQuickStylePlugin::createTheme() const
+void QQuickStylePlugin::initializeTheme(QQuickTheme *theme)
 {
-    return nullptr;
+    Q_UNUSED(theme);
 }
 
 QUrl QQuickStylePlugin::resolvedUrl(const QString &fileName) const
diff --git a/src/quickcontrols2/qquickstyleplugin_p.h b/src/quickcontrols2/qquickstyleplugin_p.h
index 735341df..6b89926c 100644
--- a/src/quickcontrols2/qquickstyleplugin_p.h
+++ b/src/quickcontrols2/qquickstyleplugin_p.h
@@ -64,12 +64,8 @@ public:
     explicit QQuickStylePlugin(QObject *parent = nullptr);
     ~QQuickStylePlugin();
 
-    void registerTypes(const char *uri) override;
-    void initializeEngine(QQmlEngine *engine, const char *uri) override;
-
-    bool isCurrent() const;
     virtual QString name() const;
-    virtual QQuickTheme *createTheme() const;
+    virtual void initializeTheme(QQuickTheme *theme);
 
     QUrl resolvedUrl(const QString &fileName) const;
 
diff --git a/src/quicktemplates2/qquicktheme.cpp b/src/quicktemplates2/qquicktheme.cpp
index b8ced7b9..1ea0cef2 100644
--- a/src/quicktemplates2/qquicktheme.cpp
+++ b/src/quicktemplates2/qquicktheme.cpp
@@ -94,26 +94,6 @@ static QPlatformTheme::Palette platformPalette(QQuickTheme::Scope scope)
     }
 }
 
-const QFont *QQuickThemePrivate::resolveThemeFont(QQuickTheme::Scope scope)
-{
-    Q_Q(QQuickTheme);
-    if (!hasResolved) {
-        q->resolve();
-        hasResolved = true;
-    }
-    return fonts[scope].data();
-}
-
-const QPalette *QQuickThemePrivate::resolveThemePalette(QQuickTheme::Scope scope)
-{
-    Q_Q(QQuickTheme);
-    if (!hasResolved) {
-        q->resolve();
-        hasResolved = true;
-    }
-    return palettes[scope].data();
-}
-
 QQuickTheme::QQuickTheme()
     : d_ptr(new QQuickThemePrivate)
 {
@@ -133,7 +113,7 @@ QFont QQuickTheme::font(Scope scope)
 {
     const QFont *font = nullptr;
     if (QQuickTheme *theme = instance())
-        font = QQuickThemePrivate::get(theme)->resolveThemeFont(scope);
+        font = QQuickThemePrivate::get(theme)->fonts[scope].data();
     else if (QPlatformTheme *theme = QGuiApplicationPrivate::platformTheme())
         font = theme->font(platformFont(scope));
 
@@ -154,7 +134,7 @@ QPalette QQuickTheme::palette(Scope scope)
 {
     const QPalette *palette = nullptr;
     if (QQuickTheme *theme = instance())
-        palette = QQuickThemePrivate::get(theme)->resolveThemePalette(scope);
+        palette = QQuickThemePrivate::get(theme)->palettes[scope].data();
     else if (QPlatformTheme *theme = QGuiApplicationPrivate::platformTheme())
         palette = theme->palette(platformPalette(scope));
 
@@ -183,8 +163,4 @@ void QQuickTheme::setPalette(Scope scope, const QPalette &palette)
     d->palettes[scope] = QSharedPointer<QPalette>::create(d->defaultPalette ? d->defaultPalette->resolve(palette) : palette);
 }
 
-void QQuickTheme::resolve()
-{
-}
-
 QT_END_NAMESPACE
diff --git a/src/quicktemplates2/qquicktheme_p.h b/src/quicktemplates2/qquicktheme_p.h
index 44610c09..d51cc5b6 100644
--- a/src/quicktemplates2/qquicktheme_p.h
+++ b/src/quicktemplates2/qquicktheme_p.h
@@ -61,7 +61,7 @@ class Q_QUICKTEMPLATES2_PRIVATE_EXPORT QQuickTheme
 {
 public:
     QQuickTheme();
-    virtual ~QQuickTheme();
+    ~QQuickTheme();
 
     static QQuickTheme *instance();
 
@@ -90,12 +90,9 @@ public:
     static QFont font(Scope scope);
     static QPalette palette(Scope scope);
 
-protected:
     void setFont(Scope scope, const QFont &font);
     void setPalette(Scope scope, const QPalette &palette);
 
-    virtual void resolve();
-
 private:
     Q_DISABLE_COPY(QQuickTheme)
     Q_DECLARE_PRIVATE(QQuickTheme)
diff --git a/src/quicktemplates2/qquicktheme_p_p.h b/src/quicktemplates2/qquicktheme_p_p.h
index 6a32440f..c7421677 100644
--- a/src/quicktemplates2/qquicktheme_p_p.h
+++ b/src/quicktemplates2/qquicktheme_p_p.h
@@ -62,14 +62,10 @@ public:
         return theme->d_func();
     }
 
-    const QFont *resolveThemeFont(QQuickTheme::Scope scope);
-    const QPalette *resolveThemePalette(QQuickTheme::Scope scope);
-
     static QScopedPointer<QQuickTheme> instance;
 
     static const int NScopes = QQuickTheme::Tumbler + 1;
 
-    bool hasResolved = false;
     QScopedPointer<const QFont> defaultFont;
     QScopedPointer<const QPalette> defaultPalette;
     QSharedPointer<QFont> fonts[NScopes];
diff --git a/tests/auto/font/tst_font.cpp b/tests/auto/font/tst_font.cpp
index 6746e39e..84f6334b 100644
--- a/tests/auto/font/tst_font.cpp
+++ b/tests/auto/font/tst_font.cpp
@@ -222,7 +222,7 @@ class TestFontTheme : public QQuickTheme
 public:
     static const int NFonts = QQuickTheme::Tumbler + 1;
 
-    void resolve() override
+    TestFontTheme()
     {
         for (int i = 0; i < NFonts; ++i) {
             QFont font = QFont();
diff --git a/tests/auto/palette/tst_palette.cpp b/tests/auto/palette/tst_palette.cpp
index ab7d9b16..e91fd732 100644
--- a/tests/auto/palette/tst_palette.cpp
+++ b/tests/auto/palette/tst_palette.cpp
@@ -221,7 +221,7 @@ class TestTheme : public QQuickTheme
 public:
     static const int NPalettes = QQuickTheme::Tumbler + 1;
 
-    void resolve() override
+    TestTheme()
     {
         for (int i = 0; i < NPalettes; ++i)
             setPalette(static_cast<Scope>(i), QPalette(QColor::fromRgb(i)));
diff --git a/tests/auto/qquickapplicationwindow/tst_qquickapplicationwindow.cpp b/tests/auto/qquickapplicationwindow/tst_qquickapplicationwindow.cpp
index 4ab3be4e..dec32e36 100644
--- a/tests/auto/qquickapplicationwindow/tst_qquickapplicationwindow.cpp
+++ b/tests/auto/qquickapplicationwindow/tst_qquickapplicationwindow.cpp
@@ -558,7 +558,7 @@ void tst_QQuickApplicationWindow::font()
 class TestTheme : public QQuickTheme
 {
 public:
-    void resolve() override
+    TestTheme()
     {
         setFont(System, QFont("Courier"));
     }