Platform theme: fill QPalette::AccentColor with OS value

The AccentColor role, added in Qt 6.6, is currently populated with a
default value.

This patch implements populating the brush with OS values for Windows
and macOS.

Change-Id: Ic243c3b8664d50db3a2096a034de6ba672d9e2d2
Reviewed-by: Axel Spoerl <axel.spoerl@qt.io>

src/plugins/platforms/cocoa/qcocoatheme.mm

@@ -94,6 +94,9 @@ static QPalette *qt_mac_createSystemPalette()
     palette->setColor(QPalette::Inactive, QPalette::PlaceholderText, qc);
     palette->setColor(QPalette::Disabled, QPalette::PlaceholderText, qc);
 
+    qc = qt_mac_toQColor([NSColor controlAccentColor]);
+    palette->setColor(QPalette::AccentColor, qc);
+
     return palette;
 }
 

src/plugins/platforms/windows/qwindowstheme.cpp

@@ -221,28 +221,48 @@ static QColor placeHolderColor(QColor textColor)
     return textColor;
 }
 
+[[maybe_unused]] [[nodiscard]] static inline QColor qt_accentColor()
+{
+    const QWinRegistryKey registry(HKEY_CURRENT_USER, LR"(Software\Microsoft\Windows\DWM)");
+    if (!registry.isValid())
+        return {};
+    const QVariant value = registry.value(L"AccentColor");
+    if (!value.isValid())
+        return {};
+    // The retrieved value is in the #AABBGGRR format, we need to
+    // convert it to the #AARRGGBB format which Qt expects.
+    const QColor abgr = QColor::fromRgba(qvariant_cast<DWORD>(value));
+    if (!abgr.isValid())
+        return {};
+    return QColor::fromRgb(abgr.blue(), abgr.green(), abgr.red(), abgr.alpha());
+}
+
 /*
     This is used when the theme is light mode, and when the theme is dark but the
     application doesn't support dark mode. In the latter case, we need to check.
 */
 void QWindowsTheme::populateLightSystemBasePalette(QPalette &result)
 {
-    QColor background = getSysColor(COLOR_BTNFACE);
+    const QColor background = getSysColor(COLOR_BTNFACE);
-    QColor textColor = getSysColor(COLOR_WINDOWTEXT);
+    const QColor textColor = getSysColor(COLOR_WINDOWTEXT);
-    QColor accent = getSysColor(COLOR_HIGHLIGHT);
 
 #if QT_CONFIG(cpp_winrt)
     // respect the Windows 11 accent color
     using namespace winrt::Windows::UI::ViewManagement;
     const auto settings = UISettings();
 
-    accent = getSysColor(settings.GetColorValue(UIColorType::Accent));
+    const QColor accent = getSysColor(settings.GetColorValue(UIColorType::Accent));
+    const QColor accentDarkest = getSysColor(settings.GetColorValue(UIColorType::AccentDark3));
+#else
+    const QColor accent = qt_accentColor();
+    const QColor accentDarkest = accent.darker(120 * 120 * 120);
 #endif
 
+    const QColor linkColor = accent;
     const QColor btnFace = background;
     const QColor btnHighlight = getSysColor(COLOR_BTNHIGHLIGHT);
 
-    result.setColor(QPalette::Highlight, accent);
+    result.setColor(QPalette::Highlight, getSysColor(COLOR_HIGHLIGHT));
     result.setColor(QPalette::WindowText, getSysColor(COLOR_WINDOWTEXT));
     result.setColor(QPalette::Button, btnFace);
     result.setColor(QPalette::Light, btnHighlight);
@@ -257,9 +277,10 @@ void QWindowsTheme::populateLightSystemBasePalette(QPalette &result)
     result.setColor(QPalette::Midlight, getSysColor(COLOR_3DLIGHT));
     result.setColor(QPalette::Shadow, getSysColor(COLOR_3DDKSHADOW));
     result.setColor(QPalette::HighlightedText, getSysColor(COLOR_HIGHLIGHTTEXT));
+    result.setColor(QPalette::AccentColor, accent);
 
-    result.setColor(QPalette::Link, Qt::blue);
+    result.setColor(QPalette::Link, linkColor);
-    result.setColor(QPalette::LinkVisited, Qt::magenta);
+    result.setColor(QPalette::LinkVisited, accentDarkest);
     result.setColor(QPalette::Inactive, QPalette::Button, result.button().color());
     result.setColor(QPalette::Inactive, QPalette::Window, result.window().color());
     result.setColor(QPalette::Inactive, QPalette::Light, result.light().color());
@@ -293,19 +314,18 @@ static void populateDarkSystemBasePalette(QPalette &result)
     const QColor accentLight = getSysColor(settings.GetColorValue(UIColorType::AccentLight1));
     const QColor accentLighter = getSysColor(settings.GetColorValue(UIColorType::AccentLight2));
     const QColor accentLightest = getSysColor(settings.GetColorValue(UIColorType::AccentLight3));
-    const QColor linkColor = accent;
 #else
     const QColor foreground = Qt::white;
     const QColor background = QColor(0x1E, 0x1E, 0x1E);
-    const QColor accent = QColor(0x00, 0x55, 0xff);
+    const QColor accent = qt_accentColor();
     const QColor accentDark = accent.darker(120);
     const QColor accentDarker = accentDark.darker(120);
     const QColor accentDarkest = accentDarker.darker(120);
     const QColor accentLight = accent.lighter(120);
     const QColor accentLighter = accentLight.lighter(120);
     const QColor accentLightest = accentLighter.lighter(120);
-    const QColor linkColor = Qt::blue;
 #endif
+    const QColor linkColor = accent;
     const QColor buttonColor = background.lighter(200);
 
     result.setColor(QPalette::All, QPalette::WindowText, foreground);
@@ -331,6 +351,7 @@ static void populateDarkSystemBasePalette(QPalette &result)
     result.setColor(QPalette::All, QPalette::ToolTipBase, buttonColor);
     result.setColor(QPalette::All, QPalette::ToolTipText, foreground.darker(120));
     result.setColor(QPalette::All, QPalette::PlaceholderText, placeHolderColor(foreground));
+    result.setColor(QPalette::All, QPalette::AccentColor, accent);
 }
 
 static QPalette systemPalette(bool light)
@@ -346,6 +367,8 @@ static QPalette systemPalette(bool light)
                         result.color(QPalette::Inactive, QPalette::Window));
         result.setColor(QPalette::Inactive, QPalette::HighlightedText,
                         result.color(QPalette::Inactive, QPalette::Text));
+        result.setColor(QPalette::Inactive, QPalette::AccentColor,
+                        result.color(QPalette::Inactive, QPalette::Window));
     }
 
     const QColor disabled = mixColors(result.windowText().color(), result.button().color());
@@ -359,6 +382,7 @@ static QPalette systemPalette(bool light)
     result.setColor(QPalette::Disabled, QPalette::ButtonText, disabled);
     result.setColor(QPalette::Disabled, QPalette::Highlight, result.color(QPalette::Highlight));
     result.setColor(QPalette::Disabled, QPalette::HighlightedText, result.color(QPalette::HighlightedText));
+    result.setColor(QPalette::Disabled, QPalette::AccentColor, disabled);
     result.setColor(QPalette::Disabled, QPalette::Base, result.window().color());
     return result;
 }
@@ -549,7 +573,6 @@ void QWindowsTheme::clearPalettes()
 
 void QWindowsTheme::refreshPalettes()
 {
-
     if (!QGuiApplication::desktopSettingsAware())
         return;
     const bool light =
@@ -567,19 +590,15 @@ void QWindowsTheme::refreshPalettes()
         const QColor accent = getSysColor(settings.GetColorValue(UIColorType::Accent));
         const QColor accentLight = getSysColor(settings.GetColorValue(UIColorType::AccentLight1));
         const QColor accentDarkest = getSysColor(settings.GetColorValue(UIColorType::AccentDark3));
+#else
+        const QColor accent = qt_accentColor();
+        const QColor accentLight = accent.lighter(120);
+        const QColor accentDarkest = accent.darker(120 * 120 * 120);
+#endif
         m_palettes[CheckBoxPalette] = new QPalette(*m_palettes[SystemPalette]);
         m_palettes[CheckBoxPalette]->setColor(QPalette::Active, QPalette::Base, accent);
         m_palettes[CheckBoxPalette]->setColor(QPalette::Active, QPalette::Button, accentLight);
         m_palettes[CheckBoxPalette]->setColor(QPalette::Inactive, QPalette::Base, accentDarkest);
-#else
-        m_palettes[ButtonPalette] = new QPalette(*m_palettes[SystemPalette]);
-        m_palettes[ButtonPalette]->setColor(QPalette::Button, QColor(0x666666u));
-        const QColor checkBoxBlue(0x0078d7u);
-        m_palettes[CheckBoxPalette] = new QPalette(*m_palettes[SystemPalette]);
-        m_palettes[CheckBoxPalette]->setColor(QPalette::Base, checkBoxBlue);
-        m_palettes[CheckBoxPalette]->setColor(QPalette::Button, checkBoxBlue);
-        m_palettes[CheckBoxPalette]->setColor(QPalette::ButtonText, Qt::white);
-#endif
         m_palettes[RadioButtonPalette] = new QPalette(*m_palettes[CheckBoxPalette]);
     }
 }