Clean up qwindowdefs_win.h

The file lives in Qt Gui, but declares a few methods from
Qt Core and Widgets. All of those methods are actually mostly
unused, not documented and pretty trivial.

This patch removes the last few places the methods got used and
removes the declarations. The implementations should get removed
in a future release.

Change-Id: I2b609c29f403d2ed4824ff4346008be08b3fd067
Reviewed-by: Marc Mutz <marc.mutz@kdab.com>

src/corelib/kernel/qcoreapplication_win.cpp

@@ -122,6 +122,7 @@ QString QCoreApplicationPrivate::appName() const
 
 #ifndef Q_OS_WINRT
 
+#if QT_VERSION < QT_VERSION_CHECK(6, 0, 0)
 Q_CORE_EXPORT HINSTANCE qWinAppInst()                // get Windows app handle
 {
     return GetModuleHandle(0);
@@ -145,6 +146,7 @@ Q_CORE_EXPORT int qWinAppCmdShow()                        // get main window sho
         : SW_SHOWDEFAULT;
 #endif
 }
+#endif
 
 /*****************************************************************************
   qWinMain() - Initializes Windows. Called from WinMain() in qtmain_win.cpp

src/corelib/kernel/qeventdispatcher_win.cpp

@@ -55,7 +55,6 @@
 
 QT_BEGIN_NAMESPACE
 
-HINSTANCE qWinAppInst();
 extern uint qGlobalPostedEventsCount();
 
 #ifndef TIME_KILL_SYNCHRONOUS
@@ -310,7 +309,7 @@ QWindowsMessageWindowClassContext::QWindowsMessageWindowClassContext()
     wc.lpfnWndProc = qt_internal_proc;
     wc.cbClsExtra = 0;
     wc.cbWndExtra = 0;
-    wc.hInstance = qWinAppInst();
+    wc.hInstance = GetModuleHandle(0);
     wc.hIcon = 0;
     wc.hCursor = 0;
     wc.hbrBackground = 0;
@@ -327,7 +326,7 @@ QWindowsMessageWindowClassContext::QWindowsMessageWindowClassContext()
 QWindowsMessageWindowClassContext::~QWindowsMessageWindowClassContext()
 {
     if (className) {
-        UnregisterClass(className, qWinAppInst());
+        UnregisterClass(className, GetModuleHandle(0));
         delete [] className;
     }
 }
@@ -345,7 +344,7 @@ static HWND qt_create_internal_window(const QEventDispatcherWin32 *eventDispatch
                             0, 0, 0, 0,        // geometry
                             HWND_MESSAGE,            // parent
                             0,                 // menu handle
-                            qWinAppInst(),     // application
+                            GetModuleHandle(0),     // application
                             0);                // windows creation data.
 
     if (!wnd) {

src/gui/kernel/qwindowdefs_win.h

@@ -111,13 +111,4 @@ typedef long HRESULT;
 
 typedef struct tagMSG MSG;
 
-QT_BEGIN_NAMESPACE
-
-Q_CORE_EXPORT HINSTANCE qWinAppInst();
-Q_CORE_EXPORT HINSTANCE qWinAppPrevInst();
-Q_CORE_EXPORT int       qWinAppCmdShow();
-Q_WIDGETS_EXPORT HDC           qt_win_display_dc();
-
-QT_END_NAMESPACE
-
 #endif // QWINDOWDEFS_WIN_H

src/widgets/kernel/qapplication.cpp

@@ -868,6 +868,7 @@ QApplication::~QApplication()
 #endif
 }
 
+#if QT_VERSION < QT_VERSION_CHECK(6, 0, 0)
 #if defined(Q_OS_WIN) && !defined(Q_OS_WINRT)
 // #fixme: Remove.
 static HDC         displayDC        = 0;                // display device context
@@ -880,6 +881,7 @@ Q_WIDGETS_EXPORT HDC qt_win_display_dc()                        // get display D
     return displayDC;
 }
 #endif
+#endif
 
 void qt_cleanup()
 {
@@ -887,12 +889,14 @@ void qt_cleanup()
     QColormap::cleanup();
 
     QApplicationPrivate::active_window = 0; //### this should not be necessary
+#if QT_VERSION < QT_VERSION_CHECK(6, 0, 0)
 #if defined(Q_OS_WIN) && !defined(Q_OS_WINRT)
     if (displayDC) {
         ReleaseDC(0, displayDC);
         displayDC = 0;
     }
 #endif
+#endif
 }
 
 /*!

src/widgets/styles/qwindowsxpstyle.cpp

@@ -451,8 +451,11 @@ HBITMAP QWindowsXPStylePrivate::buffer(int w, int h)
     w = qMax(bufferW, w);
     h = qMax(bufferH, h);
 
-    if (!bufferDC)
-        bufferDC = CreateCompatibleDC(qt_win_display_dc());
+    if (!bufferDC) {
+        HDC displayDC = GetDC(0);
+        bufferDC = CreateCompatibleDC(displayDC);
+        ReleaseDC(0, displayDC);
+    }
 
     // Define the header
     BITMAPINFO bmi;