init the OpenGL context in the windows backend

Change-Id: Ic4fb491c95170639015a4452f355354ad01612bc

include/vcl/opengl/OpenGLContext.hxx

@@ -164,6 +164,8 @@ public:
 // only in vcl's platform code
 #if defined( UNX ) && !defined MACOSX && !defined IOS && !defined ANDROID
     bool init(Display* dpy, Window win, int screen);
+#elif defined( _WIN32 )
+    bool init( HDC hDC, HWND hWnd );
 #endif
 
     void makeCurrent();

vcl/source/opengl/OpenGLContext.cxx

@@ -513,6 +513,16 @@ bool OpenGLContext::init(Display* dpy, Window win, int screen)
 
     return ImplInit();
 }
+#elif defined( _WIN32 )
+bool OpenGLContext::init(HDC hDC, HWND hWnd)
+{
+    if (mbInitialized)
+        return false;
+
+    m_aGLWin.hDC = hDC;
+    m_aGLWin.hWnd = hWnd;
+    return ImplInit();
+}
 #endif
 
 bool OpenGLContext::ImplInit()
@@ -524,7 +534,6 @@ bool OpenGLContext::ImplInit()
     m_aGLWin.Height = 0;
 
 #if defined( WNT )
-    m_aGLWin.hDC = GetDC(m_aGLWin.hWnd);
 #elif defined( MACOSX )
 
 #elif defined( IOS )
@@ -778,6 +787,7 @@ bool OpenGLContext::initWindow()
         m_aGLWin.hWnd = sysData->hWnd;
     }
 
+    m_aGLWin.hDC = GetDC(m_aGLWin.hWnd);
     return true;
 }
 

vcl/win/source/gdi/salgdi.cxx

@@ -483,6 +483,12 @@ void WinSalGraphics::InitGraphics()
     ::SetTextAlign( getHDC(), TA_BASELINE | TA_LEFT | TA_NOUPDATECP );
     ::SetBkMode( getHDC(), WIN32_TRANSPARENT );
     ::SetROP2( getHDC(), R2_COPYPEN );
+
+    OpenGLSalGraphicsImpl* pImpl = dynamic_cast<OpenGLSalGraphicsImpl*>(mpImpl.get());
+    if (pImpl)
+    {
+        pImpl->GetOpenGLContext().init(mhLocalDC, mhWnd);
+    }
 }
 
 void WinSalGraphics::DeInitGraphics()