ColorScheme: consolidate dark mode handling on Windows into Theme

Move storage of whether dark mode is set into a static class member
of QWindowsTheme, and remove QWindowsContext::isDarkMode; ask the
theme instead using the colorScheme() implementation, which will return
the stored value.

Move the code handling settings changes into QWindowsTheme as well.

Task-number: QTBUG-124490
Change-Id: I4795e80b6ab2c94701385dc84771e9ad5578cf32
Reviewed-by: Oliver Wolff <oliver.wolff@qt.io>
Reviewed-by: Wladimir Leuschner <wladimir.leuschner@qt.io>
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@qt.io>

src/plugins/platforms/windows/qwindowsapplication.cpp

@@ -74,7 +74,7 @@ bool QWindowsApplication::setWinTabEnabled(bool enabled)
 
 bool QWindowsApplication::isDarkMode() const
 {
-    return QWindowsContext::isDarkMode();
+    return QWindowsTheme::instance()->colorScheme() == Qt::ColorScheme::Dark;
 }
 
 QWindowsApplication::DarkModeHandling QWindowsApplication::darkModeHandling() const

src/plugins/platforms/windows/qwindowscontext.cpp

@@ -154,11 +154,9 @@ struct QWindowsContextPrivate {
     bool m_asyncExpose = false;
     HPOWERNOTIFY m_powerNotification = nullptr;
     HWND m_powerDummyWindow = nullptr;
-    static bool m_darkMode;
     static bool m_v2DpiAware;
 };
 
-bool QWindowsContextPrivate::m_darkMode = false;
 bool QWindowsContextPrivate::m_v2DpiAware = false;
 
 QWindowsContextPrivate::QWindowsContextPrivate()
@@ -172,7 +170,6 @@ QWindowsContextPrivate::QWindowsContextPrivate()
         m_systemInfo |= QWindowsContext::SI_RTL_Extensions;
         m_keyMapper.setUseRTLExtensions(true);
     }
-    m_darkMode = QWindowsTheme::queryDarkMode();
     if (FAILED(m_oleInitializeResult)) {
        qWarning() << "QWindowsContext: OleInitialize() failed: "
            << QSystemError::windowsComString(m_oleInitializeResult);
@@ -464,11 +461,6 @@ bool QWindowsContext::setProcessDpiAwareness(QtWindows::DpiAwareness dpiAwarenes
     return true;
 }
 
-bool QWindowsContext::isDarkMode()
-{
-    return QWindowsContextPrivate::m_darkMode;
-}
-
 QWindowsContext *QWindowsContext::instance()
 {
     return m_instance;
@@ -1093,21 +1085,7 @@ bool QWindowsContext::windowsProc(HWND hwnd, UINT message,
         // Only refresh the window theme if the user changes the personalize settings.
         if ((wParam == 0) && (lParam != 0) // lParam sometimes may be NULL.
             && (wcscmp(reinterpret_cast<LPCWSTR>(lParam), L"ImmersiveColorSet") == 0)) {
-            const bool darkMode = QWindowsTheme::queryDarkMode();
+            QWindowsTheme::handleSettingsChanged();
-            const bool darkModeChanged = darkMode != QWindowsContextPrivate::m_darkMode;
-            QWindowsContextPrivate::m_darkMode = darkMode;
-            auto integration = QWindowsIntegration::instance();
-            integration->updateApplicationBadge();
-            if (integration->darkModeHandling().testFlag(QWindowsApplication::DarkModeStyle)) {
-                QWindowsTheme::instance()->refresh();
-                QWindowSystemInterface::handleThemeChange();
-            }
-            if (darkModeChanged) {
-                if (integration->darkModeHandling().testFlag(QWindowsApplication::DarkModeWindowFrames)) {
-                    for (QWindowsWindow *w : d->m_windows)
-                        w->setDarkBorder(QWindowsContextPrivate::m_darkMode);
-                }
-            }
         }
         return d->m_screenManager.handleScreenChanges();
     }

src/plugins/platforms/windows/qwindowscontext.h

@@ -120,8 +120,6 @@ public:
     static QtWindows::DpiAwareness processDpiAwareness();
     static QtWindows::DpiAwareness windowDpiAwareness(HWND hwnd);
 
-    static bool isDarkMode();
-
     void setDetectAltGrModifier(bool a);
 
     // Returns a combination of SystemInfoFlags

src/plugins/platforms/windows/qwindowsintegration.cpp

@@ -642,7 +642,8 @@ void QWindowsIntegration::setApplicationBadge(qint64 number)
         return;
     }
 
-    const bool isDarkMode = QWindowsContext::isDarkMode();
+    const bool isDarkMode = QWindowsTheme::instance()->colorScheme()
+                         == Qt::ColorScheme::Dark;
 
     QColor badgeColor;
     QColor textColor;

src/plugins/platforms/windows/qwindowstheme.cpp

@@ -13,6 +13,7 @@
 #  include "qwindowssystemtrayicon.h"
 #endif
 #include "qwindowsscreen.h"
+#include "qwindowswindow.h"
 #include <commctrl.h>
 #include <objbase.h>
 #include <commoncontrols.h>
@@ -451,6 +452,7 @@ QWindowsTheme *QWindowsTheme::m_instance = nullptr;
 QWindowsTheme::QWindowsTheme()
 {
     m_instance = this;
+    s_darkMode = QWindowsTheme::queryDarkMode();
     std::fill(m_fonts, m_fonts + NFonts, nullptr);
     std::fill(m_palettes, m_palettes + NPalettes, nullptr);
     refresh();
@@ -542,7 +544,26 @@ Qt::ColorScheme QWindowsTheme::colorScheme() const
 {
     if (queryHighContrast())
         return Qt::ColorScheme::Unknown;
-    return QWindowsContext::isDarkMode() ? Qt::ColorScheme::Dark : Qt::ColorScheme::Light;
+    return s_darkMode ? Qt::ColorScheme::Dark : Qt::ColorScheme::Light;
+}
+
+void QWindowsTheme::handleSettingsChanged()
+{
+    const bool darkMode = QWindowsTheme::queryDarkMode();
+    const bool darkModeChanged = darkMode != QWindowsTheme::s_darkMode;
+    s_darkMode = darkMode;
+    auto integration = QWindowsIntegration::instance();
+    integration->updateApplicationBadge();
+    if (integration->darkModeHandling().testFlag(QWindowsApplication::DarkModeStyle)) {
+        QWindowsTheme::instance()->refresh();
+        QWindowSystemInterface::handleThemeChange();
+    }
+    if (darkModeChanged) {
+        if (integration->darkModeHandling().testFlag(QWindowsApplication::DarkModeWindowFrames)) {
+            for (QWindowsWindow *w : std::as_const(QWindowsContext::instance()->windows()))
+                w->setDarkBorder(s_darkMode);
+        }
+    }
 }
 
 void QWindowsTheme::clearPalettes()
@@ -556,7 +577,7 @@ void QWindowsTheme::refreshPalettes()
     if (!QGuiApplication::desktopSettingsAware())
         return;
     const bool light =
-        !QWindowsContext::isDarkMode()
+        !s_darkMode
         || !QWindowsIntegration::instance()->darkModeHandling().testFlag(QWindowsApplication::DarkModeStyle);
     clearPalettes();
     m_palettes[SystemPalette] = new QPalette(QWindowsTheme::systemPalette(light ? Qt::ColorScheme::Light : Qt::ColorScheme::Dark));

src/plugins/platforms/windows/qwindowstheme.h

@@ -33,6 +33,8 @@ public:
 
     Qt::ColorScheme colorScheme() const override;
 
+    static void handleSettingsChanged();
+
     const QPalette *palette(Palette type = SystemPalette) const override
         { return m_palettes[type]; }
     const QFont *font(Font type = SystemFont) const override
@@ -71,6 +73,7 @@ private:
     void refreshIconPixmapSizes();
 
     static QWindowsTheme *m_instance;
+    static inline bool s_darkMode = false;
     QPalette *m_palettes[NPalettes];
     QFont *m_fonts[NFonts];
     QList<QSize> m_fileIconSizes;

src/plugins/platforms/windows/qwindowswindow.cpp

@@ -5,6 +5,7 @@
 
 #include "qwindowswindow.h"
 #include "qwindowscontext.h"
+#include "qwindowstheme.h"
 #if QT_CONFIG(draganddrop)
 #  include "qwindowsdrag.h"
 #endif
@@ -929,7 +930,7 @@ QWindowsWindowData
         return result;
     }
 
-    if (QWindowsContext::isDarkMode() && shouldApplyDarkFrame(w))
+    if (QWindowsTheme::instance()->colorScheme() == Qt::ColorScheme::Dark && shouldApplyDarkFrame(w))
         QWindowsWindow::setDarkBorderToWindow(result.hwnd, true);
 
     if (mirrorParentWidth != 0) {
@@ -2689,7 +2690,7 @@ bool QWindowsWindow::windowEvent(QEvent *event)
 {
     switch (event->type()) {
     case QEvent::ApplicationPaletteChange:
-        setDarkBorder(QWindowsContext::isDarkMode());
+        setDarkBorder(QWindowsTheme::instance()->colorScheme() == Qt::ColorScheme::Dark);
         break;
     case QEvent::WindowBlocked: // Blocked by another modal window.
         setEnabled(false);