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请高手帮我解读一下这段代码，在此谢过
/***************************************************************************
 * Function: ToExpand
 *
 * Purpose:
 *
 * Switch to expand view of the selected line
 */
BOOL
ToExpand(HWND hwnd)
{
        if (selection < 0) {
                return(FALSE);
        }

        if (!view_isexpanded(current_view)) {
                /* save the current outline size and position */
                WINDOWPLACEMENT wp;
                if (GetWindowPlacement(hwndClient,&wp)) {
                        WriteProfileInt(APPNAME, "OutlineShowCmd", wp.showCmd);
                        WriteProfileInt(APPNAME, "OutlineMaxX", wp.ptMaxPosition.x);
                        WriteProfileInt(APPNAME, "OutlineMaxY", wp.ptMaxPosition.y);
                        WriteProfileInt(APPNAME, "OutlineNormLeft", wp.rcNormalPosition.left);
                        WriteProfileInt(APPNAME, "OutlineNormTop", wp.rcNormalPosition.top);
                        WriteProfileInt(APPNAME, "OutlineNormRight", wp.rcNormalPosition.right);
                        WriteProfileInt(APPNAME, "OutlineNormBottom", wp.rcNormalPosition.bottom);
                        WriteProfileInt(APPNAME, "OutlineSaved", 1);
                }

                /* restore the previous expanded size and position, if any */
                if (GetProfileInt(APPNAME, "ExpandedSaved", 0)) {
                        wp.flags                   = 0;
                        wp.showCmd
                                = GetProfileInt( APPNAME, "ExpandShowCmd"
                                               , SW_SHOWMAXIMIZED);
                        wp.ptMaxPosition.x
                                = GetProfileInt( APPNAME, "ExpandMaxX", 0);
                        wp.ptMaxPosition.y
                                = GetProfileInt( APPNAME, "ExpandMaxY", 0);
                        wp.rcNormalPosition.left
                                = GetProfileInt( APPNAME, "ExpandNormLeft"
                                               , wp.rcNormalPosition.left);
                        wp.rcNormalPosition.top
                                = GetProfileInt( APPNAME, "ExpandNormTop"
                                               , wp.rcNormalPosition.top);
                        wp.rcNormalPosition.right
                                = GetProfileInt( APPNAME, "ExpandNormRight"
                                               , wp.rcNormalPosition.right);
                        wp.rcNormalPosition.bottom
                                = GetProfileInt( APPNAME, "ExpandNormBottom"
                                               , wp.rcNormalPosition.bottom);
                        SetWindowPlacement(hwndClient,&wp);
                }
                else ShowWindow(hwndClient, SW_SHOWMAXIMIZED);
        }

        /*change the view mapping to expand mode */
        if (view_expand(current_view, selection)) {

                /* ok - we now have an expanded view - change status
                 * to show this
                 */

                DisplayMode = MODE_EXPAND;

                /* resize to show the graphic bar picture */
                DoResize(hwndClient);


                /* change button,status text-if we are not still busy*/
                if (!fBusy) {
                        TCHAR szBuf[10];
                        lstrcpy(szBuf,LoadRcString(IDS_OUTLINE));
                        /* the status field when we are expanded shows the
                         * tag field (normally the file name) for the
                         * item we are expanding
                         */
                        SetStatus(view_getcurrenttag(current_view) );
                        SetButtonText(szBuf);
                }

                return(TRUE);
        }
        return(FALSE);
} /* ToExpand */

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