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 ) ;
.
.
.
}