Windows QPA: Add detection of dark mode

Read the dark mode setting and make it accessible
via native interface.
Add a command line option to set the support level.

Task-number: QTBUG-72028
Change-Id: I1e9fe296a6b1bda81512d003183038b866b67545
Reviewed-by: Oliver Wolff <oliver.wolff@qt.io>

8 files changed, 69 insertions, 2 deletions

diff --git a/src/plugins/platforms/windows/qwindowscontext.cpp b/src/plugins/platforms/windows/qwindowscontext.cpp
index c85d04b816..d322b0e92b 100644
--- a/src/plugins/platforms/windows/qwindowscontext.cpp
+++ b/src/plugins/platforms/windows/qwindowscontext.cpp
@@ -42,6 +42,7 @@
 #include "qwindowsintegration.h"
 #include "qwindowswindow.h"
 #include "qwindowskeymapper.h"
+#include "qwindowsnativeinterface.h"
 #include "qwindowsmousehandler.h"
 #include "qwindowspointerhandler.h"
 #include "qtwindowsglobal.h"
@@ -277,8 +278,11 @@ struct QWindowsContextPrivate {
     bool m_asyncExpose = false;
     HPOWERNOTIFY m_powerNotification = nullptr;
     HWND m_powerDummyWindow = nullptr;
+    static bool m_darkMode;
 };
 
+bool QWindowsContextPrivate::m_darkMode = false;
+
 QWindowsContextPrivate::QWindowsContextPrivate()
     : m_oleInitializeResult(OleInitialize(nullptr))
 {
@@ -293,6 +297,7 @@ QWindowsContextPrivate::QWindowsContextPrivate()
         m_systemInfo |= QWindowsContext::SI_RTL_Extensions;
         m_keyMapper.setUseRTLExtensions(true);
     }
+    m_darkMode = QWindowsTheme::queryDarkMode();
     if (FAILED(m_oleInitializeResult)) {
        qWarning() << "QWindowsContext: OleInitialize() failed: "
            << QWindowsContext::comErrorString(m_oleInitializeResult);
@@ -485,6 +490,11 @@ void QWindowsContext::setProcessDpiAwareness(QtWindows::ProcessDpiAwareness dpiA
     }
 }
 
+bool QWindowsContext::isDarkMode()
+{
+    return QWindowsContextPrivate::m_darkMode;
+}
+
 QWindowsContext *QWindowsContext::instance()
 {
     return m_instance;
@@ -1203,9 +1213,17 @@ bool QWindowsContext::windowsProc(HWND hwnd, UINT message,
             t->displayChanged();
         QWindowsWindow::displayChanged();
         return d->m_screenManager.handleDisplayChange(wParam, lParam);
-    case QtWindows::SettingChangedEvent:
+    case QtWindows::SettingChangedEvent: {
         QWindowsWindow::settingsChanged();
+        const bool darkMode = QWindowsTheme::queryDarkMode();
+        if (darkMode != QWindowsContextPrivate::m_darkMode) {
+            QWindowsContextPrivate::m_darkMode = darkMode;
+            auto nativeInterface =
+                static_cast<QWindowsNativeInterface *>(QWindowsIntegration::instance()->nativeInterface());
+            emit nativeInterface->darkModeChanged(darkMode);
+        }
         return d->m_screenManager.handleScreenChanges();
+    }
     default:
         break;
     }
diff --git a/src/plugins/platforms/windows/qwindowscontext.h b/src/plugins/platforms/windows/qwindowscontext.h
index 43ab8416ab..1831ac6ec0 100644
--- a/src/plugins/platforms/windows/qwindowscontext.h
+++ b/src/plugins/platforms/windows/qwindowscontext.h
@@ -226,6 +226,8 @@ public:
     void setProcessDpiAwareness(QtWindows::ProcessDpiAwareness dpiAwareness);
     static int processDpiAwareness();
 
+    static bool isDarkMode();
+
     void setDetectAltGrModifier(bool a);
 
     // Returns a combination of SystemInfoFlags
diff --git a/src/plugins/platforms/windows/qwindowsintegration.cpp b/src/plugins/platforms/windows/qwindowsintegration.cpp
index 32bd29a842..4b4047ac0c 100644
--- a/src/plugins/platforms/windows/qwindowsintegration.cpp
+++ b/src/plugins/platforms/windows/qwindowsintegration.cpp
@@ -219,6 +219,10 @@ static inline unsigned parseOptions(const QStringList &paramList,
             options |= QWindowsIntegration::DontUseWMPointer;
         } else if (param == u"reverse") {
             options |= QWindowsIntegration::RtlEnabled;
+        } else if (param == u"darkmode=1") {
+            options |= QWindowsIntegration::DarkModeWindowFrames;
+        } else if (param == u"darkmode=2") {
+            options |= QWindowsIntegration::DarkModeWindowFrames | QWindowsIntegration::DarkModeStyle;
         } else {
             qWarning() << "Unknown option" << param;
         }
diff --git a/src/plugins/platforms/windows/qwindowsintegration.h b/src/plugins/platforms/windows/qwindowsintegration.h
index b49d21022b..1f16d13769 100644
--- a/src/plugins/platforms/windows/qwindowsintegration.h
+++ b/src/plugins/platforms/windows/qwindowsintegration.h
@@ -70,7 +70,9 @@ public:
         NoNativeMenus = 0x200,
         DontUseWMPointer = 0x400,
         DetectAltGrModifier = 0x800,
-        RtlEnabled = 0x1000
+        RtlEnabled = 0x1000,
+        DarkModeWindowFrames = 0x2000,
+        DarkModeStyle = 0x4000
     };
 
     explicit QWindowsIntegration(const QStringList &paramList);
diff --git a/src/plugins/platforms/windows/qwindowsnativeinterface.cpp b/src/plugins/platforms/windows/qwindowsnativeinterface.cpp
index d1d181d66e..1195f15a59 100644
--- a/src/plugins/platforms/windows/qwindowsnativeinterface.cpp
+++ b/src/plugins/platforms/windows/qwindowsnativeinterface.cpp
@@ -47,6 +47,7 @@
 #include "qwindowsopengltester.h"
 #include "qwindowsintegration.h"
 #include "qwindowsmime.h"
+#include "qwindowstheme.h"
 #include "qwin10helpers.h"
 
 #include <QtGui/qwindow.h>
@@ -316,4 +317,15 @@ QVariant QWindowsNativeInterface::gpuList() const
     return result;
 }
 
+bool QWindowsNativeInterface::isDarkMode() const
+{
+    return QWindowsContext::isDarkMode();
+}
+
+// Dark mode support level 2 (style)
+bool QWindowsNativeInterface::isDarkModeStyle() const
+{
+    return (QWindowsIntegration::instance()->options() & QWindowsIntegration::DarkModeStyle) != 0;
+}
+
 QT_END_NAMESPACE
diff --git a/src/plugins/platforms/windows/qwindowsnativeinterface.h b/src/plugins/platforms/windows/qwindowsnativeinterface.h
index ce395dc5a4..90ba7a44c9 100644
--- a/src/plugins/platforms/windows/qwindowsnativeinterface.h
+++ b/src/plugins/platforms/windows/qwindowsnativeinterface.h
@@ -65,6 +65,8 @@ class QWindowsNativeInterface : public QPlatformNativeInterface
 {
     Q_OBJECT
     Q_PROPERTY(bool asyncExpose READ asyncExpose WRITE setAsyncExpose)
+    Q_PROPERTY(bool darkMode READ isDarkMode STORED false NOTIFY darkModeChanged)
+    Q_PROPERTY(bool darkModeStyle READ isDarkModeStyle STORED false)
     Q_PROPERTY(QVariant gpu READ gpu STORED false)
     Q_PROPERTY(QVariant gpuList READ gpuList STORED false)
 
@@ -92,6 +94,9 @@ public:
     bool asyncExpose() const;
     void setAsyncExpose(bool value);
 
+    bool isDarkMode() const;
+    bool isDarkModeStyle() const;
+
     QVariant gpu() const;
     QVariant gpuList() const;
 
@@ -109,6 +114,9 @@ public:
 
     QFunctionPointer platformFunction(const QByteArray &function) const override;
 
+Q_SIGNALS:
+    void darkModeChanged(bool);
+
 private:
     static QWindowsWindowFunctions::WindowActivationBehavior m_windowActivationBehavior;
 };
diff --git a/src/plugins/platforms/windows/qwindowstheme.cpp b/src/plugins/platforms/windows/qwindowstheme.cpp
index 010aea2068..2f9dd0b40b 100644
--- a/src/plugins/platforms/windows/qwindowstheme.cpp
+++ b/src/plugins/platforms/windows/qwindowstheme.cpp
@@ -63,6 +63,7 @@
 #include <QtCore/qcoreapplication.h>
 #include <QtCore/qdebug.h>
 #include <QtCore/qtextstream.h>
+#include <QtCore/qoperatingsystemversion.h>
 #include <QtCore/qsysinfo.h>
 #include <QtCore/qcache.h>
 #include <QtCore/qthread.h>
@@ -78,6 +79,7 @@
 #include <QtFontDatabaseSupport/private/qwindowsfontdatabase_p.h>
 #include <private/qhighdpiscaling_p.h>
 #include <private/qsystemlibrary_p.h>
+#include <private/qwinregistry_p.h>
 
 #include <algorithm>
 
@@ -946,6 +948,23 @@ bool QWindowsTheme::useNativeMenus()
     return result;
 }
 
+bool QWindowsTheme::queryDarkMode()
+{
+    if (QOperatingSystemVersion::current()
+        < QOperatingSystemVersion(QOperatingSystemVersion::Windows, 10, 0, 17763)
+        || queryHighContrast()) {
+        return false;
+    }
+    const auto setting = QWinRegistryKey(HKEY_CURRENT_USER, LR"(Software\Microsoft\Windows\CurrentVersion\Themes\Personalize)")
+                         .dwordValue(L"AppsUseLightTheme");
+    return setting.second && setting.first == 0;
+}
+
+bool QWindowsTheme::queryHighContrast()
+{
+    return booleanSystemParametersInfo(SPI_GETHIGHCONTRAST, false);
+}
+
 QPlatformMenuItem *QWindowsTheme::createPlatformMenuItem() const
 {
     qCDebug(lcQpaMenus) << __FUNCTION__;
diff --git a/src/plugins/platforms/windows/qwindowstheme.h b/src/plugins/platforms/windows/qwindowstheme.h
index 7a8c321da4..d557c0b4fd 100644
--- a/src/plugins/platforms/windows/qwindowstheme.h
+++ b/src/plugins/platforms/windows/qwindowstheme.h
@@ -84,6 +84,8 @@ public:
     void showPlatformMenuBar() override;
 
     static bool useNativeMenus();
+    static bool queryDarkMode();
+    static bool queryHighContrast();
 
     void refreshFonts();