Windows: Turn on dark mode support by default

The implementation was already there, and handles theme changes at
runtime as well. However, it was disabled unless the QPA parameter
"darkmode" was set to either 1 (supporting only the frame) or 2 (the
Windows theme also supports dark mode when reading the palette).

With both Windows 10 and Windows 11 now having dark mode as a fully
supported feature that is easily accessible to end-users, we should
respect that setting by default.

So change the default: support both dark window frames and palette, and
let users turn this partially off by setting darkmode=1 or darkmode=0.

This does not mean accent colors etc are fully supported by the Windows
styles.

[ChangeLog][QtGui][Windows] Dark mode, both for the window frames and
for the palette, is now supported by default. It can be turned
off (partially or entirely) by setting the QPA parameter "darkmode=0"
(no dark mode support) or "darkmode=1" (darkmode support only for the
window frames).

Pick-to: 6.4
Fixes: QTBUG-72028
Change-Id: Ia55af101896c106cde21340b306aa81390e608a2
Reviewed-by: Oliver Wolff <oliver.wolff@qt.io>

1 files changed, 5 insertions, 1 deletions

diff --git a/src/plugins/platforms/windows/qwindowsintegration.cpp b/src/plugins/platforms/windows/qwindowsintegration.cpp
index f1874b37bb..40b264d186 100644
--- a/src/plugins/platforms/windows/qwindowsintegration.cpp
+++ b/src/plugins/platforms/windows/qwindowsintegration.cpp
@@ -188,8 +188,11 @@ static inline unsigned parseOptions(const QStringList &paramList,
             options |= QWindowsIntegration::DontUseWMPointer;
         } else if (param == u"reverse") {
             options |= QWindowsIntegration::RtlEnabled;
+        } else if (param == u"darkmode=0") {
+            *darkModeHandling = {};
         } else if (param == u"darkmode=1") {
             darkModeHandling->setFlag(DarkModeHandlingFlag::DarkModeWindowFrames);
+            darkModeHandling->setFlag(DarkModeHandlingFlag::DarkModeStyle, false);
         } else if (param == u"darkmode=2") {
             darkModeHandling->setFlag(DarkModeHandlingFlag::DarkModeWindowFrames);
             darkModeHandling->setFlag(DarkModeHandlingFlag::DarkModeStyle);
@@ -209,7 +212,8 @@ void QWindowsIntegrationPrivate::parseOptions(QWindowsIntegration *q, const QStr
     QtWindows::ProcessDpiAwareness dpiAwareness = QtWindows::ProcessPerMonitorV2DpiAware;
 
     int tabletAbsoluteRange = -1;
-    DarkModeHandling darkModeHandling;
+    DarkModeHandling darkModeHandling = DarkModeHandlingFlag::DarkModeWindowFrames
+                                      | DarkModeHandlingFlag::DarkModeStyle;
     m_options = ::parseOptions(paramList, &tabletAbsoluteRange, &dpiAwareness, &darkModeHandling);
     q->setDarkModeHandling(darkModeHandling);
     QWindowsFontDatabase::setFontOptions(m_options);