Processing the WM_HSCROLL and WM_VSCROLL messages
When processing the scrolling message for a window that owns a container associated with an automation handle, the user must set the container offsets. This can be done using L_ContainerSetOffset.
The following example shows how to do this for the WM_SIZE message:
static L_VOID OnSize
(
HWND hWnd,
pCONTAINERHANDLE pContainer,
pBITMAPHANDLE pBitmap,
LPRECT prcView,
L_INT cx,
L_INT cy,
L_INT nZoom,
L_INT *pnHScroll, /*last horizontal scroll position*/
L_INT *pnVScroll /*last vertical scroll position*/
)
{
SCROLLINFO si ;
L_INT nXOffset, nYOffset ;
if ( NULL != pBitmap && pBitmap->Flags.Allocated )
{
si.cbSize = sizeof ( SCROLLINFO ) ;
si.fMask = SIF_ALL ;
// vertical scroll.
GetScrollInfo ( hWnd, SB_VERT, &si ) ;
si.nMin = 0 ;
si.nMax = BITMAPHEIGHT ( pBitmap ) ;
si.nPage = MulDiv ( cy, 100, nZoom ) ;
SetScrollInfo ( hWnd, SB_VERT, &si, TRUE ) ;
GetScrollInfo ( hWnd, SB_VERT, &si ) ;
*pnVScroll = si.nPos ;
// horizontal scroll
GetScrollInfo ( hWnd, SB_HORZ, &si ) ;
si.nMin = 0 ;
si.nMax = BITMAPWIDTH ( pBitmap ) ;
si.nPage = MulDiv ( cx, 100, nZoom ) ;
SetScrollInfo ( hWnd, SB_HORZ, &si, TRUE ) ;
GetScrollInfo ( hWnd, SB_HORZ, &si ) ;
*pnHScroll = si.nPos ;
}
else
{
si.cbSize = sizeof ( SCROLLINFO ) ;
si.fMask = SIF_RANGE ;
si.nMin = 0 ;
si.nMax = 0 ;
SetScrollInfo ( hWnd, SB_VERT, &si, TRUE ) ;
SetScrollInfo ( hWnd, SB_HORZ, &si, TRUE ) ;
*pnHScroll = 0 ;
*pnVScroll = 0 ;
}
// set the painting rectangle.
SetRect ( prcView, 0, 0, BITMAPWIDTH ( pBitmap ), BITMAPHEIGHT ( pBitmap ) ) ;
if ( nZoom < 100 )
{
nXOffset = MulDiv ( *pnHScroll, 100, nZoom ) ;
nYOffset = MulDiv ( *pnVScroll, 100, nZoom ) ;
}
else
{
nXOffset = *pnHScroll ;
nYOffset = *pnVScroll ;
}
OffsetRect ( prcView, - nXOffset, - nYOffset ) ;
prcView->left = MulDiv ( prcView->left, nZoom, 100 ) ;
prcView->top = MulDiv ( prcView->top, nZoom, 100 ) ;
prcView->right = MulDiv ( prcView->right, nZoom, 100 ) ;
prcView->bottom = MulDiv ( prcView->bottom, nZoom, 100 ) ;
L_ContainerSetOffset ( pContainer, - prcView->left, - prcView->top, 0 ) ;
}