qt: fix CompositorDCompositionAcrylicSurface causing the interface wi…

…ndow to be inactive

CompositorDCompositionAcrylicSurface creates a window itself, which makes the newly
shown interface window to be no longer active.

The interface window is just shown, it should be active. At the same time, the window
CompositorDCompositionAcrylicSurface creates is a dummy window, so it does not
make sense for it to request (and steal from the interface window) activation.

modules/gui/qt/maininterface/compositor_dcomp_acrylicsurface.cpp

@@ -319,10 +319,10 @@ try
     vlc_assert(!m_dummyWindow);
     // lDwmpCreateSharedMultiWindowVisual requires a window with disabled live (thumbnail) preview
     // use a hidden dummy window to avoid disabling live preview of main window
-    m_dummyWindow = ::CreateWindowExA(WS_EX_TOOLWINDOW, "STATIC", "dummy", WS_VISIBLE, 0, 0, 0, 0, NULL, NULL, NULL, NULL);
+    m_dummyWindow = ::CreateWindowExA(WS_EX_TOOLWINDOW, "STATIC", "dummy", 0, 0, 0, 0, 0, NULL, NULL, NULL, NULL);
     if (!m_dummyWindow)
         throw DXError("failed to create dummy window",  static_cast<HRESULT>(GetLastError()));
-
+    ShowWindow(m_dummyWindow, SW_SHOWNOACTIVATE);
     int attr = DWM_CLOAKED_APP;
     DwmSetWindowAttribute(m_dummyWindow, DWMWA_CLOAK, &attr, sizeof attr);