richedit设置滚动条位置并更新内容

想做txt阅读器时发现richedit的scrollbar位置（为了下次阅读方便，下次读取直接获取上次阅读位置）不好处理，使用GetScrollPos、SetScrollPos能够获取设置scorllbar位置的值，但是！SetScorllPos调用后只更新了scorllbar的位置richedit的内容没得到更新，google一下没有个现成的解决，只得msdn。

WM_VSCROLL重点标记一下：

However, because the SetScrollInfo, SetScrollPos, SetScrollRange, GetScrollInfo,GetScrollPos,
and GetScrollRange functions
support 32-bit scroll bar position data, there is a way to circumvent the 16-bit barrier of the WM_HSCROLL and WM_VSCROLL messages.
SeeGetScrollInfo for
a description of the technique.

GetScrollInfo重点标记一下：

SIF_TRACKPOS

Copies the current scroll box tracking position to the nTrackPosmember of the SCROLLINFO structure pointed to by lpsi.

Remarks

The GetScrollInfo function enables applications to use 32-bit scroll positions. Although the messages that indicate scroll bar position, WM_HSCROLL and WM_VSCROLL,
provide only 16 bits of position data, the functions SetScrollInfo and GetScrollInfo provide
32 bits of scroll bar position data. Thus, an application can call GetScrollInfo while processing either theWM_HSCROLL or WM_VSCROLL messages to obtain 32-bit scroll bar position data.

To get the 32-bit position of the scroll box (thumb) during a SB_THUMBTRACK request code in a WM_HSCROLL or WM_VSCROLL message,
call GetScrollInfo with the SIF_TRACKPOS value in the fMask member of the SCROLLINFO structure.
The function returns the tracking position of the scroll box in the nTrackPos member of the SCROLLINFO structure. This allows you to get the position of the scroll box as the user moves it. The following sample code illustrates
the technique.

SCROLLINFO si;
case WM_HSCROLL:
    switch(LOWORD(wparam)) {
        case SB_THUMBTRACK:
          // Initialize SCROLLINFO structure

            ZeroMemory(&si, sizeof(si));
            si.cbSize = sizeof(si);
            si.fMask = SIF_TRACKPOS;

          // Call GetScrollInfo to get current tracking
          //    position in si.nTrackPos

            if (!GetScrollInfo(hwnd, SB_HORZ, &si) )
                return 1; // GetScrollInfo failed
            break;
        .
        .
        .
    }

//保存scrollbar位置
  SCROLLINFO Info={0};
  Info.cbSize=sizeof Info;
  Info.fMask=SIF_TRACKPOS;
  GetScrollInfo(RichEdit1->Handle,SB_VERT,&Info);
  std::auto_ptr<TIniFile> ptrIni(new TIniFile(ExtractFilePath(Application->ExeName)+"Config"));
  ptrIni->WriteInteger("Reader","ScorllPos",Info.nTrackPos);

//设置scrollbar位置
    std::auto_ptr<TIniFile> ptrIni(new TIniFile(ExtractFilePath(Application->ExeName)+"Config"));
    int pos=ptrIni->ReadInteger("Reader","ScorllPos",0);
    SendMessage(RichEdit1->Handle,WM_VSCROLL,MAKEWPARAM(SB_THUMBPOSITION,pos),0);