Directx - paint mouse track problem

[qtplus]

I am trying to solve some bugs of an application I havent developed. It had developed with Directx to draw some terrain and model data. But guys combined these features with a qt widget and tried to create its terrain on a widget.
Problem is : if you run the application standalone you can draw models wherever you touch but if you use qt widgets , there is a cursor problem. You touch somewhere it models to another places.

- they canceled widget paintEngine

QPaintEngine *paintEngine() const { return NULL; }

QPaintEngine *paintEngine() const { return NULL; }

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- they setup qtwidget like:

g_hWnd= (HWND)winId();
		SceneManager::getInstance().setupViewer(g_hWnd);

g_hWnd= (HWND)winId();
		SceneManager::getInstance().setupViewer(g_hWnd);

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If i put 0 to g_hWnd : it works as standalone correctly.

they set up window like :

setAttribute( Qt::WA_OpaquePaintEvent, true);  
setAttribute( Qt::WA_PaintOnScreen, true);

setAttribute( Qt::WA_OpaquePaintEvent, true);  
setAttribute( Qt::WA_PaintOnScreen, true);

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I want to understand the reason of problem. Thanks.