Windows QPA: Provide an experimental palette for dark mode

Provide a simple palette for dark mode, implementing
dark mode support level 2.

Task-number: QTBUG-72028
Change-Id: I6f71870b251ccb7da30c01abb22c224e600f2b27
Reviewed-by: Oliver Wolff <oliver.wolff@qt.io>

src/plugins/platforms/windows/qwindowscontext.cpp

@@ -1226,6 +1226,11 @@ bool QWindowsContext::windowsProc(HWND hwnd, UINT message,
                 for (QWindowsWindow *w : d->m_windows)
                     w->setDarkBorder(QWindowsContextPrivate::m_darkMode);
             }
+            if ((options & QWindowsIntegration::DarkModeStyle) != 0) {
+                QWindowsTheme::instance()->refresh();
+                for (QWindowsWindow *w : d->m_windows)
+                    QWindowSystemInterface::handleThemeChange(w->window());
+            }
         }
         return d->m_screenManager.handleScreenChanges();
     }

src/plugins/platforms/windows/qwindowstheme.cpp

@@ -243,6 +243,15 @@ static bool shGetFileInfoBackground(const QString &fileName, DWORD attributes,
     return result;
 }
 
+// Dark Mode constants
+enum DarkModeColors : QRgb  {
+    darkModeBtnHighlightRgb = 0xc0c0c0,
+    darkModeBtnShadowRgb = 0x808080,
+    darkModeHighlightRgb = 0x0055ff, // deviating from 0x800080
+    darkModeMenuHighlightRgb = darkModeHighlightRgb,
+    darkModeGrayTextRgb = 0x00ff00
+};
+
 // from QStyle::standardPalette
 static inline QPalette standardPalette()
 {
@@ -260,23 +269,55 @@ static inline QPalette standardPalette()
     return palette;
 }
 
-static inline QPalette systemPalette()
+static void populateLightSystemBasePalette(QPalette &result)
 {
-    QPalette result = standardPalette();
     result.setColor(QPalette::WindowText, getSysColor(COLOR_WINDOWTEXT));
-    result.setColor(QPalette::Button, getSysColor(COLOR_BTNFACE));
-    result.setColor(QPalette::Light, getSysColor(COLOR_BTNHIGHLIGHT));
+    const QColor btnFace = getSysColor(COLOR_BTNFACE);
+    result.setColor(QPalette::Button, btnFace);
+    const QColor btnHighlight = getSysColor(COLOR_BTNHIGHLIGHT);
+    result.setColor(QPalette::Light, btnHighlight);
     result.setColor(QPalette::Dark, getSysColor(COLOR_BTNSHADOW));
     result.setColor(QPalette::Mid, result.button().color().darker(150));
     result.setColor(QPalette::Text, getSysColor(COLOR_WINDOWTEXT));
-    result.setColor(QPalette::BrightText, getSysColor(COLOR_BTNHIGHLIGHT));
+    result.setColor(QPalette::BrightText, btnHighlight);
     result.setColor(QPalette::Base, getSysColor(COLOR_WINDOW));
-    result.setColor(QPalette::Window, getSysColor(COLOR_BTNFACE));
+    result.setColor(QPalette::Window, btnFace);
     result.setColor(QPalette::ButtonText, getSysColor(COLOR_BTNTEXT));
     result.setColor(QPalette::Midlight, getSysColor(COLOR_3DLIGHT));
     result.setColor(QPalette::Shadow, getSysColor(COLOR_3DDKSHADOW));
     result.setColor(QPalette::Highlight, getSysColor(COLOR_HIGHLIGHT));
     result.setColor(QPalette::HighlightedText, getSysColor(COLOR_HIGHLIGHTTEXT));
+}
+
+static void populateDarkSystemBasePalette(QPalette &result)
+{
+    const QColor darkModeWindowText = Qt::white;
+    result.setColor(QPalette::WindowText, darkModeWindowText);
+    const QColor darkModebtnFace = Qt::black;
+    result.setColor(QPalette::Button, darkModebtnFace);
+    const QColor btnHighlight = QColor(darkModeBtnHighlightRgb);
+    result.setColor(QPalette::Light, btnHighlight);
+    result.setColor(QPalette::Dark, QColor(darkModeBtnShadowRgb));
+    result.setColor(QPalette::Mid, result.button().color().darker(150));
+    result.setColor(QPalette::Text, darkModeWindowText);
+    result.setColor(QPalette::BrightText, btnHighlight);
+    result.setColor(QPalette::Base, darkModebtnFace);
+    result.setColor(QPalette::Window, darkModebtnFace);
+    result.setColor(QPalette::ButtonText, darkModeWindowText);
+    result.setColor(QPalette::Midlight, darkModeWindowText);
+    result.setColor(QPalette::Shadow, darkModeWindowText);
+    result.setColor(QPalette::Highlight, QColor(darkModeHighlightRgb));
+    result.setColor(QPalette::HighlightedText, darkModeWindowText);
+}
+
+static QPalette systemPalette(bool light)
+{
+    QPalette result = standardPalette();
+    if (light)
+        populateLightSystemBasePalette(result);
+    else
+        populateDarkSystemBasePalette(result);
+
     result.setColor(QPalette::Link, Qt::blue);
     result.setColor(QPalette::LinkVisited, Qt::magenta);
     result.setColor(QPalette::Inactive, QPalette::Button, result.button().color());
@@ -302,19 +343,19 @@ static inline QPalette systemPalette()
     result.setColor(QPalette::Disabled, QPalette::Text, disabled);
     result.setColor(QPalette::Disabled, QPalette::ButtonText, disabled);
     result.setColor(QPalette::Disabled, QPalette::Highlight,
-                    getSysColor(COLOR_HIGHLIGHT));
+                    light ? getSysColor(COLOR_HIGHLIGHT) : QColor(darkModeHighlightRgb));
     result.setColor(QPalette::Disabled, QPalette::HighlightedText,
-                    getSysColor(COLOR_HIGHLIGHTTEXT));
+                    light ? getSysColor(COLOR_HIGHLIGHTTEXT) : QColor(Qt::white));
     result.setColor(QPalette::Disabled, QPalette::Base,
                     result.window().color());
     return result;
 }
 
-static inline QPalette toolTipPalette(const QPalette &systemPalette)
+static inline QPalette toolTipPalette(const QPalette &systemPalette, bool light)
 {
     QPalette result(systemPalette);
-    const QColor tipBgColor(getSysColor(COLOR_INFOBK));
-    const QColor tipTextColor(getSysColor(COLOR_INFOTEXT));
+    const QColor tipBgColor = light ? getSysColor(COLOR_INFOBK) : QColor(Qt::black);
+    const QColor tipTextColor = light ? getSysColor(COLOR_INFOTEXT) : QColor(Qt::white);
 
     result.setColor(QPalette::All, QPalette::Button, tipBgColor);
     result.setColor(QPalette::All, QPalette::Window, tipBgColor);
@@ -339,12 +380,13 @@ static inline QPalette toolTipPalette(const QPalette &systemPalette)
     return result;
 }
 
-static inline QPalette menuPalette(const QPalette &systemPalette)
+static inline QPalette menuPalette(const QPalette &systemPalette, bool light)
 {
     QPalette result(systemPalette);
-    const QColor menuColor(getSysColor(COLOR_MENU));
-    const QColor menuTextColor(getSysColor(COLOR_MENUTEXT));
-    const QColor disabled(getSysColor(COLOR_GRAYTEXT));
+    const QColor menuColor = light ? getSysColor(COLOR_MENU) : QColor(Qt::black);
+    const QColor menuTextColor = light ? getSysColor(COLOR_MENUTEXT) : QColor(Qt::white);
+    const QColor disabled = light
+        ? getSysColor(COLOR_GRAYTEXT) : QColor(darkModeGrayTextRgb);
     // we might need a special color group for the result.
     result.setColor(QPalette::Active, QPalette::Button, menuColor);
     result.setColor(QPalette::Active, QPalette::Text, menuTextColor);
@@ -353,8 +395,10 @@ static inline QPalette menuPalette(const QPalette &systemPalette)
     result.setColor(QPalette::Disabled, QPalette::WindowText, disabled);
     result.setColor(QPalette::Disabled, QPalette::Text, disabled);
     const bool isFlat = booleanSystemParametersInfo(SPI_GETFLATMENU, false);
-    result.setColor(QPalette::Disabled, QPalette::Highlight,
-                    getSysColor(isFlat ? COLOR_MENUHILIGHT : COLOR_HIGHLIGHT));
+    const QColor highlightColor = light
+        ? (getSysColor(isFlat ? COLOR_MENUHILIGHT : COLOR_HIGHLIGHT))
+        : QColor(darkModeMenuHighlightRgb);
+    result.setColor(QPalette::Disabled, QPalette::Highlight, highlightColor);
     result.setColor(QPalette::Disabled, QPalette::HighlightedText, disabled);
     result.setColor(QPalette::Disabled, QPalette::Button,
                     result.color(QPalette::Active, QPalette::Button));
@@ -375,12 +419,12 @@ static inline QPalette menuPalette(const QPalette &systemPalette)
     return result;
 }
 
-static inline QPalette *menuBarPalette(const QPalette &menuPalette)
+static inline QPalette *menuBarPalette(const QPalette &menuPalette, bool light)
 {
     QPalette *result = nullptr;
     if (booleanSystemParametersInfo(SPI_GETFLATMENU, false)) {
         result = new QPalette(menuPalette);
-        const QColor menubar(getSysColor(COLOR_MENUBAR));
+        const QColor menubar(light ? getSysColor(COLOR_MENUBAR) : QColor(Qt::black));
         result->setColor(QPalette::Active, QPalette::Button, menubar);
         result->setColor(QPalette::Disabled, QPalette::Button, menubar);
         result->setColor(QPalette::Inactive, QPalette::Button, menubar);
@@ -487,10 +531,26 @@ void QWindowsTheme::refreshPalettes()
 
     if (!QGuiApplication::desktopSettingsAware())
         return;
-    m_palettes[SystemPalette] = new QPalette(systemPalette());
-    m_palettes[ToolTipPalette] = new QPalette(toolTipPalette(*m_palettes[SystemPalette]));
-    m_palettes[MenuPalette] = new QPalette(menuPalette(*m_palettes[SystemPalette]));
-    m_palettes[MenuBarPalette] = menuBarPalette(*m_palettes[MenuPalette]);
+    const bool light =
+        !QWindowsContext::isDarkMode()
+        || (QWindowsIntegration::instance()->options() & QWindowsIntegration::DarkModeStyle) == 0;
+    m_palettes[SystemPalette] = new QPalette(systemPalette(light));
+    m_palettes[ToolTipPalette] = new QPalette(toolTipPalette(*m_palettes[SystemPalette], light));
+    m_palettes[MenuPalette] = new QPalette(menuPalette(*m_palettes[SystemPalette], light));
+    m_palettes[MenuBarPalette] = menuBarPalette(*m_palettes[MenuPalette], light);
+    if (!light) {
+        m_palettes[ButtonPalette] = new QPalette(*m_palettes[SystemPalette]);
+        m_palettes[ButtonPalette]->setColor(QPalette::Button, QColor(0x666666u));
+        const QColor checkBoxBlue(0x0078d7u);
+        const QColor white(Qt::white);
+        m_palettes[CheckBoxPalette] = new QPalette(*m_palettes[SystemPalette]);
+        m_palettes[CheckBoxPalette]->setColor(QPalette::Window, checkBoxBlue);
+        m_palettes[CheckBoxPalette]->setColor(QPalette::Base, checkBoxBlue);
+        m_palettes[CheckBoxPalette]->setColor(QPalette::Button, checkBoxBlue);
+        m_palettes[CheckBoxPalette]->setColor(QPalette::ButtonText, white);
+        m_palettes[RadioButtonPalette] = new QPalette(*m_palettes[CheckBoxPalette]);
+
+    }
 }
 
 void QWindowsTheme::clearFonts()
@@ -499,6 +559,12 @@ void QWindowsTheme::clearFonts()
     std::fill(m_fonts, m_fonts + NFonts, nullptr);
 }
 
+void QWindowsTheme::refresh()
+{
+    refreshPalettes();
+    refreshFonts();
+}
+
 void QWindowsTheme::refreshFonts()
 {
     clearFonts();

src/plugins/platforms/windows/qwindowstheme.h

@@ -88,11 +88,11 @@ public:
     static bool queryHighContrast();
 
     void refreshFonts();
+    void refresh();
 
     static const char *name;
 
 private:
-    void refresh() { refreshPalettes(); refreshFonts(); }
     void clearPalettes();
     void refreshPalettes();
     void clearFonts();

src/plugins/styles/windowsvista/qwindowsxpstyle.cpp

@@ -225,9 +225,11 @@ static HRGN qt_hrgn_from_qregion(const QRegion &region)
 */
 bool QWindowsXPStylePrivate::useXP(bool update)
 {
-    if (!update)
-        return use_xp;
-    return use_xp = IsThemeActive() && (IsAppThemed() || !QCoreApplication::instance());
+    if (update) {
+        use_xp = IsThemeActive() && (IsAppThemed() || !QCoreApplication::instance())
+                 && !QWindowsStylePrivate::isDarkMode();
+    }
+    return use_xp;
 }
 
 /* \internal

src/widgets/styles/qwindowsstyle.cpp

@@ -84,6 +84,7 @@
 #include <qpa/qplatformscreen.h>
 #include <private/qguiapplication_p.h>
 #include <private/qhighdpiscaling_p.h>
+#include <qpa/qplatformnativeinterface.h>
 #include <private/qwidget_p.h>
 
 #include <private/qstylehelper_p.h>
@@ -127,6 +128,22 @@ qreal QWindowsStylePrivate::appDevicePixelRatio()
     return qApp->devicePixelRatio();
 }
 
+bool QWindowsStylePrivate::isDarkMode()
+{
+    bool result = false;
+#ifdef Q_OS_WIN
+    // Windows only: Return whether dark mode style support is desired and
+    // dark mode is in effect.
+    if (auto ni = QGuiApplication::platformNativeInterface()) {
+        const QVariant darkModeStyleP = ni->property("darkModeStyle");
+        result = darkModeStyleP.type() == QVariant::Bool
+                 && darkModeStyleP.value<bool>()
+                 && ni->property("darkMode").value<bool>();
+    }
+#endif
+    return result;
+}
+
 // Returns \c true if the toplevel parent of \a widget has seen the Alt-key
 bool QWindowsStylePrivate::hasSeenAlt(const QWidget *widget) const
 {

src/widgets/styles/qwindowsstyle_p_p.h

@@ -74,6 +74,7 @@ public:
     static qreal devicePixelRatio(const QWidget *widget = nullptr)
         { return widget ? widget->devicePixelRatioF() : QWindowsStylePrivate::appDevicePixelRatio(); }
     static qreal nativeMetricScaleFactor(const QWidget *widget = nullptr);
+    static bool isDarkMode();
 
     bool hasSeenAlt(const QWidget *widget) const;
     bool altDown() const { return alt_down; }