Windows: Dark mode with non-native theme now uses dark titlebar.

qView.pro

@@ -40,7 +40,7 @@ win32 {
 
     # To build without win32: qmake CONFIG+=NO_WIN32
     !CONFIG(NO_WIN32) {
-        LIBS += -lshell32 -luser32 -lole32 -lshlwapi -lgdi32
+        LIBS += -lshell32 -luser32 -lole32 -lshlwapi -lgdi32 -ldwmapi
         DEFINES += WIN32_LOADED
         message("Linked to win32 api")
     }

src/mainwindow.cpp

@@ -203,6 +203,9 @@ void MainWindow::showEvent(QShowEvent *event)
     QTimer::singleShot(0, this, [this]() {
         QVCocoaFunctions::setFullSizeContentView(windowHandle(), true);
     });
+#elif defined WIN32_LOADED
+    if (qvApp->getSettingsManager().getBoolean("nonnativetheme"))
+        QVWin32Functions::setDarkTitlebarOptIn(windowHandle(), true);
 #endif
 
     if (!menuBar()->sizeHint().isEmpty())

src/qvwin32functions.cpp

@@ -6,6 +6,7 @@
 #include "Objbase.h"
 #include "appmodel.h"
 #include "Shlwapi.h"
+#include "dwmapi.h"
 
 #include <QFileInfo>
 #include <QFile>
@@ -173,6 +174,14 @@ QString QVWin32Functions::getShortPath(const QString &path)
     return getLongOrShortPath(path, GetShortPathNameW);
 }
 
+void QVWin32Functions::setDarkTitlebarOptIn(const QWindow *window, const bool enable)
+{
+    const HWND hWnd = reinterpret_cast<HWND>(window->winId());
+    const DWORD useImmersiveDarkModeAttribute = 20;
+    const BOOL attributeValue = static_cast<BOOL>(enable);
+    DwmSetWindowAttribute(hWnd, useImmersiveDarkModeAttribute, &attributeValue, sizeof(attributeValue));
+}
+
 QByteArray QVWin32Functions::getIccProfileForWindow(const QWindow *window)
 {
     QByteArray result;

src/qvwin32functions.h

@@ -18,6 +18,8 @@ class QVWin32Functions
 
     static QString getShortPath(const QString &path);
 
+    static void setDarkTitlebarOptIn(const QWindow *window, const bool enable);
+
     static QByteArray getIccProfileForWindow(const QWindow *window);
 };