When working in an MDI environment, each window may have its own bitmap data or transformations. Therefore, the toolkit data should be set to reflect the changes.
L_VOID OnMDIActivate ( HWND hWnd, L_BOOL active, HWND hActivate, HWND hDeactivate ){PAINTXFORM XForm ;HDC hdcCompatibility ;RECT rcDCRect ;.../*set the painting toolkit data*/hdcCompatibility = GetDC ( hMDIChildWnd ) ;L_PntSetMetrics ( pPaint, hdcCompatibility, MDIChildData.pBitmap, MDIChildData.hPalette ) ;ReleaseDC ( hWnd, hdcCompatibility ) ;XForm.nZoom = MDIChildData.nZoomFactor ;XForm.nXOffset = MDIChildData.nHscroll ;XForm.nYOffset = MDIChildData.nVscroll ;L_PntSetTransformation ( pPaint, &XForm ) ;GetClientRect ( hMDIChildWnd, &rcDCRect ) ;L_PntSetDCExtents ( pPaint, &rcDCRect ) ;L_PntSetClipRgn (pPaint, MDIChildData.hClipRng ) ;...}