Fix fallback styles overwriting themes

In Qt 5, QtQuickControls2Plugin::registerTypes() was responsible for
calling initializeTheme() on each style plugin. Now that we delegate
more work to the QML engine, each style plugin calls initializeTheme()
via registerTypes().

To avoid fallback styles overwriting font and palette data set by the
current style, we need to check if the theme has been intialized before
calling initializeTheme(). To do this, we add a static
"themeInitialized" bool that QQuickStylePlugin sets to true after
calling intializeTheme() for the first time. It checks this value and
avoids calling intializeTheme() if it's true.

We also need to make QQuickStylePlugin ensure that the theme it's
initializing belongs to the current style.

Fixes: QTBUG-86303
Change-Id: Ie65e646677c78622829f4949c41cb79204cf5786
Reviewed-by: Richard Moe Gustavsen <richard.gustavsen@qt.io>

34 files changed, 317 insertions, 107 deletions

diff --git a/src/imports/.prev_CMakeLists.txt b/src/imports/.prev_CMakeLists.txt
index 473471c2..e6210be9 100644
--- a/src/imports/.prev_CMakeLists.txt
+++ b/src/imports/.prev_CMakeLists.txt
@@ -4,6 +4,7 @@ add_subdirectory(controls)
 add_subdirectory(controlsimpl)
 add_subdirectory(platform)
 add_subdirectory(templates)
+add_subdirectory(nativestyle)
 add_subdirectory(controls/default)
 add_subdirectory(controls/default/impl)
 add_subdirectory(controls/fusion)
@@ -14,3 +15,9 @@ add_subdirectory(controls/material)
 add_subdirectory(controls/material/impl)
 add_subdirectory(controls/universal)
 add_subdirectory(controls/universal/impl)
+if(MACOS)
+    add_subdirectory(controls/macos)
+endif()
+if(WIN32)
+    add_subdirectory(controls/windows)
+endif()
diff --git a/src/imports/CMakeLists.txt b/src/imports/CMakeLists.txt
index fbd1d1d0..e6210be9 100644
--- a/src/imports/CMakeLists.txt
+++ b/src/imports/CMakeLists.txt
@@ -15,7 +15,6 @@ add_subdirectory(controls/material)
 add_subdirectory(controls/material/impl)
 add_subdirectory(controls/universal)
 add_subdirectory(controls/universal/impl)
-
 if(MACOS)
     add_subdirectory(controls/macos)
 endif()
diff --git a/src/imports/controls/.prev_CMakeLists.txt b/src/imports/controls/.prev_CMakeLists.txt
index ca2ddb43..b927521b 100644
--- a/src/imports/controls/.prev_CMakeLists.txt
+++ b/src/imports/controls/.prev_CMakeLists.txt
@@ -9,8 +9,6 @@ qt_add_qml_module(qtquickcontrols2plugin
     VERSION "${CMAKE_PROJECT_VERSION}"
     DESIGNER_SUPPORTED
     CLASSNAME QtQuickControls2Plugin
-    DEPENDENCIES
-        QtQuick.Templates/2.5
     SKIP_TYPE_REGISTRATION
     IMPORTS
         QtQuick.Controls.impl/auto
diff --git a/src/imports/controls/CMakeLists.txt b/src/imports/controls/CMakeLists.txt
index 4e48373e..8a7f6cfd 100644
--- a/src/imports/controls/CMakeLists.txt
+++ b/src/imports/controls/CMakeLists.txt
@@ -10,8 +10,6 @@ qt_add_qml_module(qtquickcontrols2plugin
     VERSION "6.0" # special case
     DESIGNER_SUPPORTED
     CLASSNAME QtQuickControls2Plugin
-    DEPENDENCIES
-        QtQuick.Templates/2.5
     SKIP_TYPE_REGISTRATION
     IMPORTS
         QtQuick.Controls.impl/auto
diff --git a/src/imports/controls/default/.prev_CMakeLists.txt b/src/imports/controls/default/.prev_CMakeLists.txt
index 608f81b6..9a37f29c 100644
--- a/src/imports/controls/default/.prev_CMakeLists.txt
+++ b/src/imports/controls/default/.prev_CMakeLists.txt
@@ -8,8 +8,6 @@ qt_add_qml_module(qtquickcontrols2defaultstyleplugin
     URI "QtQuick.Controls.Default"
     VERSION "${CMAKE_PROJECT_VERSION}"
     CLASSNAME QtQuickControls2DefaultStylePlugin
-    DEPENDENCIES
-        QtQuick.Controls/2.5
     GENERATE_QMLTYPES
     SOURCES
         qquickdefaultstyle.cpp qquickdefaultstyle_p.h
diff --git a/src/imports/controls/default/CMakeLists.txt b/src/imports/controls/default/CMakeLists.txt
index 336d04c9..f7ce5d10 100644
--- a/src/imports/controls/default/CMakeLists.txt
+++ b/src/imports/controls/default/CMakeLists.txt
@@ -8,8 +8,6 @@ qt_add_qml_module(qtquickcontrols2defaultstyleplugin
     URI "QtQuick.Controls.Default"
     VERSION "6.0" # special case
     CLASSNAME QtQuickControls2DefaultStylePlugin
-    DEPENDENCIES
-        QtQuick.Controls/2.5
     GENERATE_QMLTYPES
     SOURCES
         qquickdefaultstyle.cpp qquickdefaultstyle_p.h
diff --git a/src/imports/controls/default/impl/CMakeLists.txt b/src/imports/controls/default/impl/CMakeLists.txt
index d90ef86b..e6258d13 100644
--- a/src/imports/controls/default/impl/CMakeLists.txt
+++ b/src/imports/controls/default/impl/CMakeLists.txt
@@ -8,9 +8,6 @@ qt_add_qml_module(qtquickcontrols2defaultstyleimplplugin
     URI "QtQuick.Controls.Default.impl"
     VERSION "${CMAKE_PROJECT_VERSION}"
     CLASSNAME QtQuickControls2DefaultStyleImplPlugin
-    DEPENDENCIES
-        QtQuick.Templates/6.0
-        QtQuick.Controls/6.0
     SKIP_TYPE_REGISTRATION
     GENERATE_QMLTYPES
     SOURCES
diff --git a/src/imports/controls/default/qtquickcontrols2defaultstyleplugin.cpp b/src/imports/controls/default/qtquickcontrols2defaultstyleplugin.cpp
index 6b4b3bc3..c7259a29 100644
--- a/src/imports/controls/default/qtquickcontrols2defaultstyleplugin.cpp
+++ b/src/imports/controls/default/qtquickcontrols2defaultstyleplugin.cpp
@@ -51,8 +51,7 @@ public:
     QtQuickControls2DefaultStylePlugin(QObject *parent = nullptr);
 
     QString name() const override;
-
-    void registerTypes(const char *uri) override;
+    void initializeTheme(QQuickTheme *theme) override;
 
     QQuickDefaultTheme theme;
 };
@@ -66,14 +65,9 @@ QString QtQuickControls2DefaultStylePlugin::name() const
     return QStringLiteral("Default");
 }
 
-void QtQuickControls2DefaultStylePlugin::registerTypes(const char *uri)
+void QtQuickControls2DefaultStylePlugin::initializeTheme(QQuickTheme *theme)
 {
-    QQuickStylePlugin::registerTypes(uri);
-
-    if (!QQuickTheme::instance())
-        return;
-
-    theme.initialize(QQuickTheme::instance());
+    this->theme.initialize(theme);
 }
 
 QT_END_NAMESPACE
diff --git a/src/imports/controls/fusion/qtquickcontrols2fusionstyleplugin.cpp b/src/imports/controls/fusion/qtquickcontrols2fusionstyleplugin.cpp
index 59d99afc..fcaa959e 100644
--- a/src/imports/controls/fusion/qtquickcontrols2fusionstyleplugin.cpp
+++ b/src/imports/controls/fusion/qtquickcontrols2fusionstyleplugin.cpp
@@ -52,8 +52,7 @@ public:
     QtQuickControls2FusionStylePlugin(QObject *parent = nullptr);
 
     QString name() const override;
-
-    void registerTypes(const char *uri) override;
+    void initializeTheme(QQuickTheme *theme) override;
 
     QQuickFusionTheme theme;
 };
@@ -67,14 +66,9 @@ QString QtQuickControls2FusionStylePlugin::name() const
     return QStringLiteral("Fusion");
 }
 
-void QtQuickControls2FusionStylePlugin::registerTypes(const char *uri)
+void QtQuickControls2FusionStylePlugin::initializeTheme(QQuickTheme *theme)
 {
-    QQuickStylePlugin::registerTypes(uri);
-
-    if (!QQuickTheme::instance())
-        return;
-
-    theme.initialize(QQuickTheme::instance());
+    this->theme.initialize(theme);
 }
 
 QT_END_NAMESPACE
diff --git a/src/imports/controls/imagine/impl/CMakeLists.txt b/src/imports/controls/imagine/impl/CMakeLists.txt
index a2e38302..ea75184a 100644
--- a/src/imports/controls/imagine/impl/CMakeLists.txt
+++ b/src/imports/controls/imagine/impl/CMakeLists.txt
@@ -58,7 +58,7 @@ set(qml_files
     "OpacityMask.qml"
 )
 set_source_files_properties(OpacityMask.qml PROPERTIES
-    QT_QML_SOURCE_VERSION "2.0"
+    QT_QML_SOURCE_VERSION "6.0"
 )
 
 qt6_target_qml_files(qtquickcontrols2imaginestyleimplplugin
diff --git a/src/imports/controls/imagine/qtquickcontrols2imaginestyleplugin.cpp b/src/imports/controls/imagine/qtquickcontrols2imaginestyleplugin.cpp
index 336064dd..16c3f0d7 100644
--- a/src/imports/controls/imagine/qtquickcontrols2imaginestyleplugin.cpp
+++ b/src/imports/controls/imagine/qtquickcontrols2imaginestyleplugin.cpp
@@ -53,8 +53,7 @@ public:
     QtQuickControls2ImagineStylePlugin(QObject *parent = nullptr);
 
     QString name() const override;
-
-    void registerTypes(const char *uri) override;
+    void initializeTheme(QQuickTheme *theme) override;
 
     QQuickImagineTheme theme;
 };
@@ -68,14 +67,9 @@ QString QtQuickControls2ImagineStylePlugin::name() const
     return QStringLiteral("Imagine");
 }
 
-void QtQuickControls2ImagineStylePlugin::registerTypes(const char *uri)
+void QtQuickControls2ImagineStylePlugin::initializeTheme(QQuickTheme *theme)
 {
-    QQuickStylePlugin::registerTypes(uri);
-
-    if (!QQuickTheme::instance())
-        return;
-
-    theme.initialize(QQuickTheme::instance());
+    this->theme.initialize(theme);
 }
 
 QT_END_NAMESPACE
diff --git a/src/imports/controls/macos/.prev_CMakeLists.txt b/src/imports/controls/macos/.prev_CMakeLists.txt
new file mode 100644
index 00000000..a8fca854
--- /dev/null
+++ b/src/imports/controls/macos/.prev_CMakeLists.txt
@@ -0,0 +1,100 @@
+# Generated from macos.pro.
+
+#####################################################################
+## qtquickcontrols2macosstyleplugin Plugin:
+#####################################################################
+
+qt_add_qml_module(qtquickcontrols2macosstyleplugin
+    URI "QtQuick.Controls.macOS"
+    VERSION "${CMAKE_PROJECT_VERSION}"
+    CLASSNAME QtQuickControls2MacOSStylePlugin
+    IMPORTS
+        QtQuick.Controls.Fusion/auto
+    GENERATE_QMLTYPES
+    SOURCES
+        qtquickcontrols2macosstyleplugin.cpp
+    DEFINES
+        QT_NO_CAST_FROM_ASCII
+        QT_NO_CAST_TO_ASCII
+    LIBRARIES
+        Qt::CorePrivate
+        Qt::GuiPrivate
+        Qt::QmlPrivate
+        Qt::QuickControls2Private
+        Qt::QuickPrivate
+        Qt::QuickTemplates2Private
+    PUBLIC_LIBRARIES
+        Qt::Core
+        Qt::Gui
+        Qt::Qml
+        Qt::Quick
+        Qt::QuickControls2
+        Qt::QuickTemplates2
+)
+
+#### Keys ignored in scope 1:.:.:macos.pro:<TRUE>:
+# OTHER_FILES = "qmldir" "$$QML_FILES"
+# QML_IMPORT_NAME = "QtQuick.Controls.macOS"
+# QML_IMPORT_VERSION = "$$QT_VERSION"
+# TARGETPATH = "QtQuick/Controls/macOS"
+# _REQUIREMENTS = "qtConfig(quickcontrols2-macos)"
+
+set(qml_files
+    "Button.qml"
+    "Slider.qml"
+    "GroupBox.qml"
+    "CheckBox.qml"
+    "RadioButton.qml"
+    "SpinBox.qml"
+    "TextField.qml"
+    "Frame.qml"
+    "TextArea.qml"
+    "ComboBox.qml"
+    "ScrollBar.qml"
+    "ProgressBar.qml"
+    "Dial.qml"
+)
+set_source_files_properties(Button.qml PROPERTIES
+    QT_QML_SOURCE_VERSION "6.0"
+)
+set_source_files_properties(Slider.qml PROPERTIES
+    QT_QML_SOURCE_VERSION "6.0"
+)
+set_source_files_properties(GroupBox.qml PROPERTIES
+    QT_QML_SOURCE_VERSION "6.0"
+)
+set_source_files_properties(CheckBox.qml PROPERTIES
+    QT_QML_SOURCE_VERSION "6.0"
+)
+set_source_files_properties(RadioButton.qml PROPERTIES
+    QT_QML_SOURCE_VERSION "6.0"
+)
+set_source_files_properties(SpinBox.qml PROPERTIES
+    QT_QML_SOURCE_VERSION "6.0"
+)
+set_source_files_properties(TextField.qml PROPERTIES
+    QT_QML_SOURCE_VERSION "6.0"
+)
+set_source_files_properties(Frame.qml PROPERTIES
+    QT_QML_SOURCE_VERSION "6.0"
+)
+set_source_files_properties(TextArea.qml PROPERTIES
+    QT_QML_SOURCE_VERSION "6.0"
+)
+set_source_files_properties(ComboBox.qml PROPERTIES
+    QT_QML_SOURCE_VERSION "6.0"
+)
+set_source_files_properties(ScrollBar.qml PROPERTIES
+    QT_QML_SOURCE_VERSION "6.0"
+)
+set_source_files_properties(ProgressBar.qml PROPERTIES
+    QT_QML_SOURCE_VERSION "6.0"
+)
+set_source_files_properties(Dial.qml PROPERTIES
+    QT_QML_SOURCE_VERSION "6.0"
+)
+
+qt6_target_qml_files(qtquickcontrols2macosstyleplugin
+    FILES
+        ${qml_files}
+)
diff --git a/src/imports/controls/macos/qtquickcontrols2macosstyleplugin.cpp b/src/imports/controls/macos/qtquickcontrols2macosstyleplugin.cpp
index a6a26b89..f97414ce 100644
--- a/src/imports/controls/macos/qtquickcontrols2macosstyleplugin.cpp
+++ b/src/imports/controls/macos/qtquickcontrols2macosstyleplugin.cpp
@@ -46,8 +46,8 @@ class QtQuickControls2MacOSStylePlugin : public QQuickStylePlugin
     Q_PLUGIN_METADATA(IID QQmlExtensionInterface_iid)
 
 public:
-    void registerTypes(const char *uri) override;
     QString name() const override;
+    void initializeTheme(QQuickTheme *theme) override;
 };
 
 QString QtQuickControls2MacOSStylePlugin::name() const
@@ -55,9 +55,8 @@ QString QtQuickControls2MacOSStylePlugin::name() const
     return QStringLiteral("macOS");
 }
 
-void QtQuickControls2MacOSStylePlugin::registerTypes(const char *uri)
+void QtQuickControls2MacOSStylePlugin::initializeTheme(QQuickTheme */*theme*/)
 {
-    QQuickStylePlugin::registerTypes(uri);
 }
 
 QT_END_NAMESPACE
diff --git a/src/imports/controls/material/qtquickcontrols2materialstyleplugin.cpp b/src/imports/controls/material/qtquickcontrols2materialstyleplugin.cpp
index 47e7e877..095dd6d7 100644
--- a/src/imports/controls/material/qtquickcontrols2materialstyleplugin.cpp
+++ b/src/imports/controls/material/qtquickcontrols2materialstyleplugin.cpp
@@ -52,8 +52,7 @@ public:
     QtQuickControls2MaterialStylePlugin(QObject *parent = nullptr);
 
     QString name() const override;
-
-    void registerTypes(const char *uri) override;
+    void initializeTheme(QQuickTheme *theme) override;
 
     QQuickMaterialTheme theme;
 };
@@ -67,15 +66,10 @@ QString QtQuickControls2MaterialStylePlugin::name() const
     return QStringLiteral("Material");
 }
 
-void QtQuickControls2MaterialStylePlugin::registerTypes(const char *uri)
+void QtQuickControls2MaterialStylePlugin::initializeTheme(QQuickTheme *theme)
 {
-    QQuickStylePlugin::registerTypes(uri);
-
-    if (!QQuickTheme::instance())
-        return;
-
     QQuickMaterialStyle::initGlobals();
-    theme.initialize(QQuickTheme::instance());
+    this->theme.initialize(theme);
 }
 
 QT_END_NAMESPACE
diff --git a/src/imports/controls/qtquickcontrols2plugin.cpp b/src/imports/controls/qtquickcontrols2plugin.cpp
index 47263570..85c51e4f 100644
--- a/src/imports/controls/qtquickcontrols2plugin.cpp
+++ b/src/imports/controls/qtquickcontrols2plugin.cpp
@@ -34,20 +34,14 @@
 **
 ****************************************************************************/
 
-#include <QtCore/qdir.h>
-#include <QtCore/qfile.h>
-#include <QtCore/qfileinfo.h>
-#include <QtCore/qloggingcategory.h>
-#include <QtCore/qpluginloader.h>
 #include <QtCore/private/qfileselector_p.h>
-#include <QtQml/qqmlfile.h>
-#include <QtQml/qqmlextensionplugin.h>
+#include <QtCore/qloggingcategory.h>
 #include <QtQml/qqmlengine.h>
-#include <QtQml/private/qqmldirparser_p.h>
-#include <QtQuickControls2/qquickstyle.h>
+#include <QtQml/qqmlextensionplugin.h>
+#include <QtQuickTemplates2/private/qquicktheme_p_p.h>
 #include <QtQuickControls2/private/qquickstyle_p.h>
 #include <QtQuickControls2/private/qquickstyleplugin_p.h>
-#include <QtQuickTemplates2/private/qquicktheme_p_p.h>
+#include <QtQuickControls2/qquickstyle.h>
 
 QT_BEGIN_NAMESPACE
 
@@ -134,7 +128,7 @@ void QtQuickControls2Plugin::registerTypes(const char *uri)
     if (styleName != fallbackStyleName && styleName != QLatin1String("Default")) {
         registeredFallbackStyleUri = ::fallbackStyleUri();
         qCDebug(lcQtQuickControlsStylePlugin) << "calling qmlRegisterModuleImport() to register fallback style with"
-            << "uri \"" << qtQuickControlsUri << "\" moduleMajor" << QQmlModuleImportModuleAny
+            << " uri \"" << qtQuickControlsUri << "\" moduleMajor" << QQmlModuleImportModuleAny
             << "import" << registeredFallbackStyleUri << "importMajor" << QQmlModuleImportAuto;
         // The fallback style must be a built-in style, so we match the version number.
         qmlRegisterModuleImport(qtQuickControlsUri, QQmlModuleImportModuleAny, registeredFallbackStyleUri.toUtf8().constData(),
@@ -174,7 +168,6 @@ void QtQuickControls2Plugin::unregisterTypes()
     registeredStyleUri.clear();
 
     QQuickThemePrivate::instance.reset();
-
     QQuickStylePrivate::reset();
 }
 
diff --git a/src/imports/controls/universal/qtquickcontrols2universalstyleplugin.cpp b/src/imports/controls/universal/qtquickcontrols2universalstyleplugin.cpp
index 539738dd..01074432 100644
--- a/src/imports/controls/universal/qtquickcontrols2universalstyleplugin.cpp
+++ b/src/imports/controls/universal/qtquickcontrols2universalstyleplugin.cpp
@@ -51,8 +51,7 @@ public:
     QtQuickControls2UniversalStylePlugin(QObject *parent = nullptr);
 
     QString name() const override;
-
-    void registerTypes(const char *uri) override;
+    void initializeTheme(QQuickTheme *theme) override;
 
     QQuickUniversalTheme theme;
 };
@@ -66,15 +65,10 @@ QString QtQuickControls2UniversalStylePlugin::name() const
     return QStringLiteral("Universal");
 }
 
-void QtQuickControls2UniversalStylePlugin::registerTypes(const char *uri)
+void QtQuickControls2UniversalStylePlugin::initializeTheme(QQuickTheme *theme)
 {
-    QQuickStylePlugin::registerTypes(uri);
-
-    if (!QQuickTheme::instance())
-        return;
-
     QQuickUniversalStyle::initGlobals();
-    theme.initialize(QQuickTheme::instance());
+    this->theme.initialize(theme);
 }
 
 QT_END_NAMESPACE
diff --git a/src/imports/controls/windows/.prev_CMakeLists.txt b/src/imports/controls/windows/.prev_CMakeLists.txt
new file mode 100644
index 00000000..d68839b2
--- /dev/null
+++ b/src/imports/controls/windows/.prev_CMakeLists.txt
@@ -0,0 +1,92 @@
+# Generated from windows.pro.
+
+#####################################################################
+## qtquickcontrols2windowsstyleplugin Plugin:
+#####################################################################
+
+qt_add_qml_module(qtquickcontrols2windowsstyleplugin
+    URI "QtQuick.Controls.Windows"
+    VERSION "${CMAKE_PROJECT_VERSION}"
+    CLASSNAME QtQuickControls2WindowsStylePlugin
+    IMPORTS
+        QtQuick.Controls.Fusion/auto
+    GENERATE_QMLTYPES
+    SOURCES
+        qtquickcontrols2windowsstyleplugin.cpp
+    DEFINES
+        QT_NO_CAST_FROM_ASCII
+        QT_NO_CAST_TO_ASCII
+    LIBRARIES
+        Qt::CorePrivate
+        Qt::GuiPrivate
+        Qt::QmlPrivate
+        Qt::QuickControls2Private
+        Qt::QuickPrivate
+        Qt::QuickTemplates2Private
+    PUBLIC_LIBRARIES
+        Qt::Core
+        Qt::Gui
+        Qt::Qml
+        Qt::Quick
+        Qt::QuickControls2
+        Qt::QuickTemplates2
+)
+
+#### Keys ignored in scope 1:.:.:windows.pro:<TRUE>:
+# OTHER_FILES = "qmldir" "$$QML_FILES"
+# QML_IMPORT_NAME = "QtQuick.Controls.Windows"
+# QML_IMPORT_VERSION = "$$QT_VERSION"
+# TARGETPATH = "QtQuick/Controls/Windows"
+# _REQUIREMENTS = "qtConfig(quickcontrols2-windows)"
+
+set(qml_files
+    "Button.qml"
+    "CheckBox.qml"
+    "ComboBox.qml"
+    "Frame.qml"
+    "GroupBox.qml"
+    "ProgressBar.qml"
+    "RadioButton.qml"
+    "Slider.qml"
+    "SpinBox.qml"
+    "TextArea.qml"
+    "TextField.qml"
+)
+set_source_files_properties(Button.qml PROPERTIES
+    QT_QML_SOURCE_VERSION "6.0"
+)
+set_source_files_properties(CheckBox.qml PROPERTIES
+    QT_QML_SOURCE_VERSION "6.0"
+)
+set_source_files_properties(ComboBox.qml PROPERTIES
+    QT_QML_SOURCE_VERSION "6.0"
+)
+set_source_files_properties(Frame.qml PROPERTIES
+    QT_QML_SOURCE_VERSION "6.0"
+)
+set_source_files_properties(GroupBox.qml PROPERTIES
+    QT_QML_SOURCE_VERSION "6.0"
+)
+set_source_files_properties(ProgressBar.qml PROPERTIES
+    QT_QML_SOURCE_VERSION "6.0"
+)
+set_source_files_properties(RadioButton.qml PROPERTIES
+    QT_QML_SOURCE_VERSION "6.0"
+)
+set_source_files_properties(Slider.qml PROPERTIES
+    QT_QML_SOURCE_VERSION "6.0"
+)
+set_source_files_properties(SpinBox.qml PROPERTIES
+    QT_QML_SOURCE_VERSION "6.0"
+)
+set_source_files_properties(TextArea.qml PROPERTIES
+    QT_QML_SOURCE_VERSION "6.0"
+)
+set_source_files_properties(TextField.qml PROPERTIES
+    QT_QML_SOURCE_VERSION "6.0"
+)
+
+qt6_target_qml_files(qtquickcontrols2windowsstyleplugin
+    FILES
+        ${qml_files}
+)
diff --git a/src/imports/controls/windows/CMakeLists.txt b/src/imports/controls/windows/CMakeLists.txt
index 749d19a2..6bcbc26c 100644
--- a/src/imports/controls/windows/CMakeLists.txt
+++ b/src/imports/controls/windows/CMakeLists.txt
@@ -45,6 +45,7 @@ set(qml_files
     "ComboBox.qml"
     "Frame.qml"
     "GroupBox.qml"
+    "ProgressBar.qml"
     "RadioButton.qml"
     "Slider.qml"
     "SpinBox.qml"
@@ -66,6 +67,9 @@ set_source_files_properties(Frame.qml PROPERTIES
 set_source_files_properties(GroupBox.qml PROPERTIES
     QT_QML_SOURCE_VERSION "6.0"
 )
+set_source_files_properties(ProgressBar.qml PROPERTIES
+    QT_QML_SOURCE_VERSION "6.0"
+)
 set_source_files_properties(RadioButton.qml PROPERTIES
     QT_QML_SOURCE_VERSION "6.0"
 )
diff --git a/src/imports/controls/windows/qtquickcontrols2windowsstyleplugin.cpp b/src/imports/controls/windows/qtquickcontrols2windowsstyleplugin.cpp
index 9c50f4fb..1136cd9a 100644
--- a/src/imports/controls/windows/qtquickcontrols2windowsstyleplugin.cpp
+++ b/src/imports/controls/windows/qtquickcontrols2windowsstyleplugin.cpp
@@ -46,8 +46,8 @@ class QtQuickControls2WindowsStylePlugin : public QQuickStylePlugin
     Q_PLUGIN_METADATA(IID QQmlExtensionInterface_iid)
 
 public:
-    void registerTypes(const char *uri) override;
     QString name() const override;
+    void initializeTheme(QQuickTheme *theme) override;
 };
 
 QString QtQuickControls2WindowsStylePlugin::name() const
@@ -55,9 +55,8 @@ QString QtQuickControls2WindowsStylePlugin::name() const
     return QStringLiteral("Windows");
 }
 
-void QtQuickControls2WindowsStylePlugin::registerTypes(const char *uri)
+void QtQuickControls2WindowsStylePlugin::initializeTheme(QQuickTheme */*theme*/)
 {
-    QQuickStylePlugin::registerTypes(uri);
 }
 
 QT_END_NAMESPACE
diff --git a/src/imports/controlsimpl/.prev_CMakeLists.txt b/src/imports/controlsimpl/.prev_CMakeLists.txt
index 58f7ad8c..ec51260d 100644
--- a/src/imports/controlsimpl/.prev_CMakeLists.txt
+++ b/src/imports/controlsimpl/.prev_CMakeLists.txt
@@ -8,8 +8,6 @@ qt_add_qml_module(qtquickcontrols2implplugin
     URI "QtQuick.Controls.impl"
     VERSION "${CMAKE_PROJECT_VERSION}"
     CLASSNAME QtQuickControls2ImplPlugin
-    DEPENDENCIES
-        QtQuick.Templates/2.5
     SKIP_TYPE_REGISTRATION
     SOURCES
         qtquickcontrols2implplugin.cpp
diff --git a/src/imports/controlsimpl/CMakeLists.txt b/src/imports/controlsimpl/CMakeLists.txt
index 7b65cccb..86966168 100644
--- a/src/imports/controlsimpl/CMakeLists.txt
+++ b/src/imports/controlsimpl/CMakeLists.txt
@@ -8,8 +8,6 @@ qt_add_qml_module(qtquickcontrols2implplugin
     URI "QtQuick.Controls.impl"
     VERSION "6.0" # special case
     CLASSNAME QtQuickControls2ImplPlugin
-    DEPENDENCIES
-        QtQuick.Templates/2.5
     SKIP_TYPE_REGISTRATION
     SOURCES
         qtquickcontrols2implplugin.cpp
diff --git a/src/imports/nativestyle/qtquickcontrols2nativestyleplugin.cpp b/src/imports/nativestyle/qtquickcontrols2nativestyleplugin.cpp
index d6e77d5f..ef8bfb9f 100644
--- a/src/imports/nativestyle/qtquickcontrols2nativestyleplugin.cpp
+++ b/src/imports/nativestyle/qtquickcontrols2nativestyleplugin.cpp
@@ -62,7 +62,7 @@ public:
     ~QtQuickControls2NativeStylePlugin() override;
 
     void initializeEngine(QQmlEngine *engine, const char *uri) override;
-    void registerTypes(const char *uri) override;
+    void initializeTheme(QQuickTheme *theme) override;
     QString name() const override;
 };
 
@@ -136,14 +136,8 @@ void QtQuickControls2NativeStylePlugin::initializeEngine(QQmlEngine *engine, con
     QQuickNativeStyle::setStyle(style);
 }
 
-void QtQuickControls2NativeStylePlugin::registerTypes(const char *uri)
+void QtQuickControls2NativeStylePlugin::initializeTheme(QQuickTheme */*theme*/)
 {
-    Q_UNUSED(uri);
-    if (!QQuickTheme::instance())
-        return;
-
-    QQuickTheme::instance()->setPalette(QQuickTheme::System, QPalette());
-    QQuickTheme::instance()->setFont(QQuickTheme::System, QFont());
 }
 
 QT_END_NAMESPACE
diff --git a/src/imports/templates/.prev_CMakeLists.txt b/src/imports/templates/.prev_CMakeLists.txt
index 178906d7..948a4327 100644
--- a/src/imports/templates/.prev_CMakeLists.txt
+++ b/src/imports/templates/.prev_CMakeLists.txt
@@ -8,8 +8,6 @@ qt_add_qml_module(qtquicktemplates2plugin
     URI "QtQuick.Templates"
     VERSION "${CMAKE_PROJECT_VERSION}"
     CLASSNAME QtQuickTemplates2Plugin
-    DEPENDENCIES
-        QtQuick.Window/2.2
     SKIP_TYPE_REGISTRATION
     SOURCES
         qtquicktemplates2plugin.cpp
diff --git a/src/imports/templates/CMakeLists.txt b/src/imports/templates/CMakeLists.txt
index f37f69a8..4c250cae 100644
--- a/src/imports/templates/CMakeLists.txt
+++ b/src/imports/templates/CMakeLists.txt
@@ -8,8 +8,6 @@ qt_add_qml_module(qtquicktemplates2plugin
     URI "QtQuick.Templates"
     VERSION "6.0" # special case
     CLASSNAME QtQuickTemplates2Plugin
-    DEPENDENCIES
-        QtQuick.Window/2.2
     SKIP_TYPE_REGISTRATION
     SOURCES
         qtquicktemplates2plugin.cpp
diff --git a/src/quickcontrols2/qquickstyle.cpp b/src/quickcontrols2/qquickstyle.cpp
index fd81d1dd..ec0b5e48 100644
--- a/src/quickcontrols2/qquickstyle.cpp
+++ b/src/quickcontrols2/qquickstyle.cpp
@@ -142,6 +142,9 @@ struct QQuickStyleSpec
 
     void setFallbackStyle(const QString &fallback, const QByteArray &method)
     {
+        if (!fallback.isEmpty())
+            qCDebug(lcQtQuickControlsStyle) << "fallback style" << fallback << "set on QQuickStyleSpec via" << method;
+
         fallbackStyle = fallback;
         fallbackMethod = method;
     }
diff --git a/src/quickcontrols2/qquickstyleplugin.cpp b/src/quickcontrols2/qquickstyleplugin.cpp
index 657b31fc..f211d4b0 100644
--- a/src/quickcontrols2/qquickstyleplugin.cpp
+++ b/src/quickcontrols2/qquickstyleplugin.cpp
@@ -41,7 +41,6 @@
 #include <QtCore/qloggingcategory.h>
 #include <QtQml/qqmlengine.h>
 #include <QtQml/qqmlfile.h>
-
 #include <QtQuickTemplates2/private/qquicktheme_p_p.h>
 
 QT_BEGIN_NAMESPACE
@@ -57,17 +56,24 @@ QQuickStylePlugin::~QQuickStylePlugin()
 {
 }
 
-QString QQuickStylePlugin::name() const
-{
-    return QString();
-}
-
 void QQuickStylePlugin::registerTypes(const char *uri)
 {
     qCDebug(lcStylePlugin).nospace() << "registerTypes called with uri " << uri << "; plugin name is " << name();
 
-    if (!QQuickTheme::instance())
+    auto theme = QQuickTheme::instance();
+    if (!theme) {
         qWarning() << "QtQuick.Controls must be imported before importing" << baseUrl().toString();
+        return;
+    }
+
+    if (name() != QQuickStyle::name()) {
+        qCDebug(lcStylePlugin).nospace() << "theme does not belong to current style ("
+            << QQuickStyle::name() << "); not calling initializeTheme()";
+        return;
+    }
+
+    qCDebug(lcStylePlugin) << "theme has not been initialized; calling initializeTheme()";
+    initializeTheme(theme);
 }
 
 void QQuickStylePlugin::unregisterTypes()
diff --git a/src/quickcontrols2/qquickstyleplugin_p.h b/src/quickcontrols2/qquickstyleplugin_p.h
index 37d070db..1a941aa7 100644
--- a/src/quickcontrols2/qquickstyleplugin_p.h
+++ b/src/quickcontrols2/qquickstyleplugin_p.h
@@ -63,7 +63,8 @@ public:
     explicit QQuickStylePlugin(QObject *parent = nullptr);
     ~QQuickStylePlugin();
 
-    virtual QString name() const;
+    virtual QString name() const = 0;
+    virtual void initializeTheme(QQuickTheme *theme) = 0;
 
     void registerTypes(const char *uri) override;
     void unregisterTypes() override;
diff --git a/tests/auto/styleimports/CMakeLists.txt b/tests/auto/styleimports/CMakeLists.txt
index b5910e92..86db761a 100644
--- a/tests/auto/styleimports/CMakeLists.txt
+++ b/tests/auto/styleimports/CMakeLists.txt
@@ -24,6 +24,7 @@ qt_add_test(tst_styleimports
         Qt::GuiPrivate
         Qt::QmlPrivate
         Qt::QuickControls2
+        Qt::QuickControls2ImplPrivate
         Qt::QuickControls2Private
         Qt::QuickPrivate
         Qt::QuickTemplates2Private
@@ -33,13 +34,19 @@ qt_add_test(tst_styleimports
 
 # Resources:
 set(qmake_resourcestyle_resource_files
-    "ResourceStyle/Button.qml"
-    "ResourceStyle/qmldir"
+    "resources/ResourceStyle/Button.qml"
+    "resources/ResourceStyle/qmldir"
+)
+set(qmake_resourcestyle_resource_files
+    "ResourceStyle/Button.qml" # special case: QTBUG-86726
+    "ResourceStyle/qmldir" # special case
 )
 
 qt_add_resource(tst_styleimports "qmake_resourcestyle"
     PREFIX
         "/"
+    BASE
+        "resources"
     FILES
         ${qmake_resourcestyle_resource_files}
 )
diff --git a/tests/auto/styleimports/data/platformSelectors.qml b/tests/auto/styleimports/data/applicationWindowWithButton.qml
index ba6af22c..ba6af22c 100644
--- a/tests/auto/styleimports/data/platformSelectors.qml
+++ b/tests/auto/styleimports/data/applicationWindowWithButton.qml
diff --git a/tests/auto/styleimports/resources/ResourceStyle/Button.qml b/tests/auto/styleimports/resources/ResourceStyle/Button.qml
new file mode 100644
index 00000000..3a97e9de
--- /dev/null
+++ b/tests/auto/styleimports/resources/ResourceStyle/Button.qml
@@ -0,0 +1,9 @@
+import QtQuick.Controls.impl 2.15
+import QtQuick.Templates 2.15 as T
+T.Button {
+    objectName: "ResourceStyle"
+
+    contentItem: IconLabel {
+        color: "salmon"
+    }
+}
diff --git a/tests/auto/styleimports/ResourceStyle/qmldir b/tests/auto/styleimports/resources/ResourceStyle/qmldir
index 4cb1a835..4cb1a835 100644
--- a/tests/auto/styleimports/ResourceStyle/qmldir
+++ b/tests/auto/styleimports/resources/ResourceStyle/qmldir
diff --git a/tests/auto/styleimports/styleimports.pro b/tests/auto/styleimports/styleimports.pro
index 774d93e9..398ce7c2 100644
--- a/tests/auto/styleimports/styleimports.pro
+++ b/tests/auto/styleimports/styleimports.pro
@@ -4,14 +4,15 @@ SOURCES += tst_styleimports.cpp
 
 macos:CONFIG -= app_bundle
 
-QT += core-private gui-private qml-private quick-private quickcontrols2-private testlib
+QT += core-private gui-private qml-private quick-private quickcontrols2-private quickcontrols2impl-private testlib
 
 include (../shared/util.pri)
 
 resourcestyle.prefix = /
+resourcestyle.base = resources
 resourcestyle.files += \
-    $$PWD/ResourceStyle/Button.qml \
-    $$PWD/ResourceStyle/qmldir
+    $$PWD/resources/ResourceStyle/Button.qml \
+    $$PWD/resources/ResourceStyle/qmldir
 RESOURCES += resourcestyle
 
 TESTDATA = data/*
diff --git a/tests/auto/styleimports/tst_styleimports.cpp b/tests/auto/styleimports/tst_styleimports.cpp
index 8b47dee7..fa524098 100644
--- a/tests/auto/styleimports/tst_styleimports.cpp
+++ b/tests/auto/styleimports/tst_styleimports.cpp
@@ -43,6 +43,7 @@
 #include <QtQuick/qquickwindow.h>
 #include <QtQuickControls2/qquickstyle.h>
 #include <QtQuickControls2/private/qquickstyle_p.h>
+#include <QtQuickControls2Impl/private/qquickiconlabel_p.h>
 
 #include "../shared/util.h"
 
@@ -62,6 +63,9 @@ private slots:
 
     void importStyleWithoutControls_data();
     void importStyleWithoutControls();
+
+    void fallbackStyleShouldNotOverwriteTheme_data();
+    void fallbackStyleShouldNotOverwriteTheme();
 };
 
 void tst_StyleImports::initTestCase()
@@ -151,6 +155,7 @@ void tst_StyleImports::select()
     QQuickStyle::setFallbackStyle(fallback);
 
     QQmlEngine engine;
+    engine.addImportPath(QLatin1String(":/"));
     engine.addImportPath(directory());
     engine.addImportPath(dataDirectory());
     QQmlComponent component(&engine);
@@ -185,7 +190,7 @@ void tst_StyleImports::platformSelectors()
 
     QQmlApplicationEngine engine;
     engine.addImportPath(dataDirectory());
-    engine.load(testFileUrl("platformSelectors.qml"));
+    engine.load(testFileUrl("applicationWindowWithButton.qml"));
     QQuickWindow *window = qobject_cast<QQuickWindow*>(engine.rootObjects().first());
     QVERIFY(window);
 
@@ -241,6 +246,46 @@ void tst_StyleImports::importStyleWithoutControls()
     QTRY_VERIFY(success);
 }
 
+void tst_StyleImports::fallbackStyleShouldNotOverwriteTheme_data()
+{
+    QTest::addColumn<QString>("style");
+    QTest::addColumn<QString>("fallbackStyle");
+    QTest::addColumn<QColor>("expectedContentItemColor");
+
+    QTest::addRow("style=Fusion,fallbackStyle=Material")
+        << QString::fromLatin1("Fusion") << QString::fromLatin1("Material") << QColor::fromRgb(0x252525);
+    QTest::addRow("style=ResourceStyle,fallbackStyle=Material")
+        << QString::fromLatin1("ResourceStyle") << QString::fromLatin1("Material") << QColor("salmon");
+}
+
+void tst_StyleImports::fallbackStyleShouldNotOverwriteTheme()
+{
+    QFETCH(QString, style);
+    QFETCH(QString, fallbackStyle);
+    QFETCH(QColor, expectedContentItemColor);
+
+    QQuickStyle::setStyle(style);
+    QQuickStyle::setFallbackStyle(fallbackStyle);
+
+    QQmlApplicationEngine engine;
+    engine.addImportPath(QLatin1String(":/"));
+    engine.addImportPath(dataDirectory());
+    engine.load(testFileUrl("applicationWindowWithButton.qml"));
+    QVERIFY(!engine.rootObjects().isEmpty());
+    QQuickWindow *window = qobject_cast<QQuickWindow*>(engine.rootObjects().first());
+    QVERIFY(window);
+
+    QObject *button = window->property("button").value<QObject*>();
+    QVERIFY(button);
+
+    QQuickIconLabel *contentItem = button->property("contentItem").value<QQuickIconLabel*>();
+    QVERIFY(contentItem);
+
+    // For example: the Fusion style provides Button.qml, so the Button's text color
+    // should be that of QPalette::ButtonText from QQuickFusionTheme.
+    QCOMPARE(contentItem->color(), expectedContentItemColor);
+}
+
 QTEST_MAIN(tst_StyleImports)
 
 #include "tst_styleimports.moc"
diff --git a/tests/manual/nativestyle/main.cpp b/tests/manual/nativestyle/main.cpp
index 536625fb..4925efa8 100644
--- a/tests/manual/nativestyle/main.cpp
+++ b/tests/manual/nativestyle/main.cpp
@@ -55,7 +55,7 @@ int main(int argc, char *argv[])
 #elif defined(Q_OS_WINDOWS)
         QQuickStyle::setStyle("Windows");
 #else
-        QQuickStyle::setStyle("FusionDesktop");
+        QQuickStyle::setStyle("Fusion");
 #endif
 
     QQmlApplicationEngine engine;