vcl: use resetToReInitialize to avoid context problems on Windows.

It appears that we have to do this for VirtualDevices, where we have
freed / re-allocated the underlying resource, or we fail to switch the
current context, and render to the wrong place, before blatting a
blank texture over the top of it.

Change-Id: I0253f216ea7dc9786374dc83ca38f4f6295e3035

vcl/opengl/gdiimpl.cxx

@@ -105,6 +105,15 @@ void OpenGLSalGraphicsImpl::Init()
         maOffscreenTex.GetHeight() != GetHeight() )
     {
         maOffscreenTex = OpenGLTexture();
+#if defined(WNT)
+        // URGH ... VirtualDevice may have destroyed the underlying resource
+        // our context is associated with - FIXME: can we do better here ?
+        if (mpContext)
+        {
+            mpContext->resetToReInitialize();
+            ReleaseContext();
+        }
+#endif
     }
 }
 

vcl/source/opengl/OpenGLContext.cxx

@@ -621,6 +621,17 @@ bool OpenGLContext::init(SystemChildWindow* pChildWindow)
     return ImplInit();
 }
 
+#if defined( WNT )
+// FIXME share resetToReInitialize() across platforms...
+void OpenGLContext::resetToReInitialize()
+{
+    if( !mbInitialized )
+        return;
+    resetCurrent();
+    mbInitialized = false;
+}
+#endif
+
 #if defined( UNX ) && !defined MACOSX && !defined IOS && !defined ANDROID
 bool OpenGLContext::init(Display* dpy, Window win, int screen)
 {